nr's blog

Making Plans for Nigel 13 October, 2018

Filed under: Motorcycling — nr @ 8:46 pm

So, a few days ago, I was idly chatting with my mate Lippy on Facebook about this and that – it’s a regular Sunday evening thing really. We’ll start talking about bikes in some form, and just see where the conversation goes. I’ve idly spent many happy Sunday evenings just talking rubbish about bikes. Anyway, last Sunday, a group of us were chatting away, when Lippy mentioned that he had a lead on an SV650 in need of restoration, for £250. Now, call me optimistic, but that sounded like a challenge if ever there was one, so I instantly responded with “I’ll have it for that”, having never even seen a picture of it. The very next day, I got a photo:


Well, doesn’t look *that* bad, right? I mean, the paintwork is, well, not to my taste, but looks presentable enough. The motocross bars? Errr, no thanks. They’re going in the bin. That headlight unit looks like a prop from a 50p remake of Star Wars or something. That’s going to follow the bars into the same bin. And that exhaust looks to be terrifyingly, shatteringly illegal, even for race use.

Now, it’s safe to say that I wasn’t really looking for a project bike. I’m skint, after my car shat itself a few weeks back. But I have a massive soft spot for SVs, especially after racing the fabulous Darvill Racing SV at Jurby last year. So, I started putting together a plan to get up to Birmingham to collect it, and trying to work out what to actually do with it. The first part of this plan of action was made very easy when Foz dropped me a line, saying “I’ve got a van, happy to pick it up and drive it over for you”. So, earlier today, Foz and his son Bobby turned up, and we unloaded the SV, and got it out into the sunlight. We then got on with the important business of drinking tea, eating bacon & black pudding butties, and then having another cuppa to wash it down with. Foz & Bobby then headed back home, and I started to put together a plan of action.

First thing, obviously, is to see if it runs. And there are myriad reasons that I’m not even going to attempt to start it yet. Firstly, the wiring is quite horrifically bodged in places, and really needs a good going over. I have a spare ECU and loom, but I suspect that whatever was causing it not to run is down to electrical bodgery, rather than an ECU failure. And I’m in the very happy position of having some mates with excellent knowledge of the SV650, having either invented the Minitwins race series, or built, from the ground up, some very competitive bikes. Already I’ve had some brilliant guidance on where to start looking for lack-of-sparky-action problems. Secondly, the fuel system needs a good seeing too. The carbs are pretty gunged up, and really need a good stripping and cleaning up. And, finally, I need to check to see if there’s any oil in there…

Secure in the knowledge that this is a 20yr old Suzuki, and therefore pretty much every fastener will be seized, I dived in. And it’s safe to say that this bike has had a very hard life. Bodge upon bodge was unveiled, and while some of them just need cleaning up and putting back together properly (like the wiring for example), some will require either some fabrication or looking for s/hand parts (footrests for example) and at least one bodge is irreversible, and may cause a few headaches later on – one of the front fairing mounts has been removed. Bother. But, of course, none of this matters if I can’t get the thing running, which is where I am now. The airbox and carbs are currently off. The engine turns over when cranked by hand. And the wiring is being methodically checked, and un-bodged where necessary. It’s going to be a good while before it runs, as there’s a lot more un-bodging to complete, but it’s all therapeutic work, and will keep me out of mischief for a while.

Assuming it does run, what am I going to do with it? I did, for one moment, think of turning it into a trackday bike. But, that would be epically stupid, as I don’t do trackdays. No, this will go back on the road. And I’m not going to just stick a stubby seat unit on there and call it a café racer. No, that’s been done with a million other SVs. And it’s certainly not going back on the road with the existing paintwork on there. Plans will come along, I’m sure. I’ve seen some things that I like the look of, but I’m not going to start thinking about bodywork and paint yet. There are too many other things to think about right now. And if it’s beyond a financially sensible repair to get it running again (I suspect it’ll be fine, but I’m being pragmatic about this), I’ll just sell the parts on, and get my money back.

So, I’ve ended up with something that really, should be on the scrapheap. It should have been there a long time ago. It’s loud, gaudy, and in this day and age, of no use at all. Yet, inexplicably it’s been given a second chance, no doubt to be kicked and sworn at repeatedly. There are so many better options available. Really, there is no good reason to take this path at all. I know it will let me down when tough questions are asked of it.

Now, what should I call it?

Postscript: Thinking about it, and I know I probably shouldn’t do this, but I’m going to keep a running total of costs, and a wishlist of things that I need.  So, here goes:

Running Total

  • Bike: £250


  • Bucket of deox
  • Industrial strength degreaser
  • Willpower of a saint
  • Penetrating oil
  • Impact driver
  • Haynes Manual. (Already have the workshop manual as a .pdf, but I find the Haynes manuals to be useful to have alongside the workshop manual)

Once I’ve proven that the motor works, the wishlist will start to include things that I actually need to progress the next stage of the rebuild. But for now, until I hear the motor running, I’m not going to buy anything.



All ones and zeroes 16 September, 2018

Filed under: Motorcycling — nr @ 11:42 am

Blimey, it’s been a while, hasn’t it? All sorts of stuff has happened in the past few months, and I’ve really been a bit lazy with regard to keeping this lot updated. If you cast your mind back to, erm, July, I mentioned that I had plans for some track time and a quick jaunt to France. Both of those things did indeed happen, but in time honoured fashion, I’m not going to talk about them just yet. No, the first thing I want to talk about is this:


Yup, I’ve finally brought the TRX kicking and screaming (well, farting and droning) into the digital age, with a lovely Ignitech programmable ignition unit. Actually getting hold of this is another story in its own right, which I’m sure will be told later. What’s particularly nice about this story though is that there’s another TRX850 that’s just been rescued from the great scrappy in the sky, and it’s now owned by my mate Foz. I’d originally planned to buy the bike myself, but my car threw a bearing in the rear diff, and I couldn’t justify spending the money. However, plans were rapidly thrown together with Alex from Darvill Racing and Foz, and I ended up swapping a spare stock CDI unit that I had in the garage for the Ignitech unit. So, what will this do for the bike? Well, I’m not entirely sure so far… but it does mean that I can plug it into a laptop now and pretend to be in a MotoGP paddock. Current plan is to just run the bike for a while (at least until I’ve replaced the car and let my finances recover a bit), and then take it to Spike at Cambridge Motorcycles for some dyno time, and maybe some tweaking of the advance map to suit the FCR41s. This is the first time I’ve ever owned a bike that can be tuned with a laptop rather than a set of riffler files, so I’m going to bore everyone stupid for the next six months, talking about programmable dwell times and shift light outputs.

So, looking a bit further back, we went to France. This was, undoubtedly, the highlight of the year for me. It was a bit of a trek for sure, which really started a long time before ever booking the tunnel crossing… Some time last year, my friend Michael, with whom I’d shared several good bottles of wine, many happy evenings together, and even an avalanche, suggested that Sol and me, and our families, take a trip to his place in Burgundy for a week of summer sun. This seemed like a fabulous idea, so over a large roast dinner and a couple of bottles of wine, a plot was hatched. The Lovely Faye, Sue, and the girls would all jump on a flight to Geneva, and hire a car to get to Chantisy. Meanwhile, Sol and I would ride. A proper road trip. The first challenge really was to ensure that the bikes were up to the job. I wasn’t too concerned, as I use mine for work every day anyway, but as Sol has written about on his blog, his Katana was always going to need a bit more work, as it was still in a pile of bits in the corner of his garage. Here be spiders. About five months of weapons grade procrastination followed, which was brilliantly enjoyable, but not ultimately productive, and so, a week before we were due to travel, we ended up in Sol’s garage frantically stripping forks, changing the oil, and re-lockwiring everything again.

The journey down to Michael’s place was, of course, brilliant. We left Cambridge about about midnight, got the 03:20 train, and by 05:00 or so local time, we were riding out of Calais. It’s worth mentioning at this point that Sol’s mighty Katana is probably the only bike that is louder than my TRX in the country. When we left Sol’s house at midnight, we actually walked the bikes about 100metres down the road before starting them up… Anyhow, the kilometres rolled past, and the initial bone-chilling cold soon passed as the sun rose:


Yeah. That Katana. It has 145bhp. You would, wouldn’t you?

I can’t remember how long the ride was. I think it was about 900kms or so, but it was all bloody brilliant. The only mechanical worry was the oil consumption of the TRX. It gets through about a litre per 1500kms at the speeds we were carrying, so I just had to keep topping it up every now and then. This simple sounding act is made more challenging by the design decision that Yamaha came to when they placed the oil filler on a vertical surface. I’d like to have words with the team that approved that idea.

While in France, we also had the pleasure of a nice jaunt through the Jura mountains, and over the Col de la Faucille. This was some of the best riding I’ve ever done, no question. The roads were brilliant, the scenery was exactly not like The Fens at all, and the weather was brilliant. But the best thing was following Sol. The Kat, being long, low, and brutally fast, is completely out of it’s element on these roads really, particularly when we started gaining altitude and encountering damp patches and damaged road surfaces due to the winter freeze/thaw cycle. The TRX felt beautifully nimble and surefooted on the excellent Conti SportAttack3 tyres. The Kat was obviously keeping Sol *very* occupied. I may have laughed out loud on more than one occasion as Sol brutally wrestled the recalcitrant Kat into some sort of shape to get around a corner. For sure he missed a lot of apexes, but gratifyingly, he also managed to miss the 300 metre drop on the outside of some of the corners too. All too soon though, it was time to head home, and leave Burgundy behind. As I sit here typing this, at the end of a quite extraordinary summer, I realise that I’ve fallen a little bit more hopelessly and totally in love with France. I could carry on typing for hours, I’m sure, about the discovery of the beautiful local Aligoté wine. The marvellous collection of old bikes, cars, and aeroplanes at the equally magnificent Château de Savigny-les-Beaune, and the brilliant French guy riding the Haga rep Mille who we kept seeing, scowling and straining the guts out of a disgracefully weedy little rollup cigarette on the journey home. But that would really just be self indulgent twoddle.

So, there was something else, wasn’t there? Ah, yup. Cadwell Park. The TRX did indeed make it back onto a circuit for the first time in a few years. And while it acquitted itself well, it wasn’t all beer and skittles.


The stupid Renegade exhausts limited the amount of fun that could be had, by grounding out at every opportunity. Now, given that they are appallingly badly made, and look awful, I’m even more determined to replace them with something better. Any ideas out there, I’m all ears. All that said, other than the ground clearance, the bike was lovely to ride on the track. And, I know that I’m biased, but it’s also safe to say that it was by far the best sounding bike out there. Will there be more track time in the future? Well, given that I’ve just installed a programmable ignition unit, it would be a shame not to set up an ignition map for track use, wouldn’t it?

What a brilliant summer it’s been. And I’m sure that there’s going to be a few new developments over the coming months too. Plans are afoot. On more than one front.


Everything in its right place 2 July, 2018

Filed under: Motorcycling — nr @ 12:45 pm

Looking at my whiteboard in the shed [1], among some circuit diagrams, passwords, and general scrawl, there’s a small list, neatly tucked away next to my holiday dates for the year. It looks like this:

  • ✔ Forks
  • ✔ Air Filter
  • ✔ Plug leads/caps
  • ✔ Sprocket(s)
  • ? Head Bearings
  • ✔ Reg/Rec
  • ✔ Re-pack cans
  • Tyres
  • Oil + Filter
  • Brake Pads

I’m not normally that well organised to be honest, but, well, there’s a couple of things coming up in TRX world that need things to be just so. Just right. Firstly, I’ve got a trackday at Cadwell Park coming up – I’ve not been on a track since October last year, and for all I know the TRX hasn’t been on a track since, well, the first time I rode it, back in about 2001 or so. The trackday itself shouldn’t be that hard on the bike, but rather more importantly, a few days after the trackday, I’ll be loading the bike onto the Channel Tunnel, and heading to France for a week of rest and sunshine.

So, what’s with all the things on the list then? Well, that was all the stuff that needs doing before I set off. The forks were done a while back, and I wrote about it at the time. Other than maybe putting in some thicker oil to increase the rebound damping a bit, I’m pretty happy with the way things turned out. Certainly they’re a lot better than they were, and I’m happy that I didn’t have to go the whole hog and throw something like a YZF750 front end on there. So, what else needed/still needs doing?

Air filter. Now that I’m using the bike for work pretty much every day, I need to think about longevity (and comfort!) a bit more. And while those massive unfiltered bellmouths on the FCR41s looked great, and sounded even better, it was always obvious that the engine would last longer with at least some filtering in place. A bit of looking around turned up a lovely Pipercross dual filter, that fits just perfectly:


I have a feeling that it has richened things up a little on the carburation, but nothing untoward. And the best thing (other than hopefully avoiding ingesting small rodents) is that it hasn’t affected the induction noise at all. It still sounds for all the world like God’s vacuum cleaner when you give the throttle a vicious twist.

Plug leads/caps. I was always painfully aware that the old plug leads were just that. Old. And it’s a quick and cheap thing to replace with something a lot newer, so why not? And at the same time, replace the resistors in the plug caps with some brass rod. The plugs already have resistors in there, so there’s really no need for further resistance in the plug caps. I’ve heard all sorts of reasons as to why these are actually there, from suppressing RF interference to allowing lower octane fuel to be used. In the absence of any actual information, I put them to one side and fitted the bits of brass rod in place. And whether it was the new leads, or losing the resistors, it definitely had an impact on the running of the bike. Throttle response is now smoother, and starting is easier. Highly recommended to anyone else with a TRX who’s reading this.

Sprocket. When I rebuilt the thing, I replaced the 525 chain and sprockets with a 520 set by JT. With hindsight, this was a mistake. The chain was junk, and I ended up replacing it after about 2000 miles with a DID chain, which is lasting so much better. And the rear sprocket was a 42T jobbie, from an NX650, as opposed to the stock 39T of the TRX. On the track, this was probably fine (the bike came with a 42T when I picked it up) but on the road, the 42T is pretty short. Particularly with the low first gear of the TDM gearbox. And while this was entertaining for unexpected wheelies, it did get a bit tiresome after a while. So, I needed a 39T rear sprocket, to fit a TRX850, but 520 rather than 525. No chance. I had to get one made – stand up and take a bow B&C express, who handled the making of a beautiful, hard anodized sprocket to fit. It looks great, and it just makes the bike a lot more pleasant to ride on long motorway trips too. The 42T may get refitted for the Cadwell trackday, but I doubt it. The motor feels so un-revvy that I doubt gearing will be critical. Besides, this is a trackday, not a race. There are no prizes for first place.

Head bearings. I’m still unsure about this. For a while I was plagued with a clunky front end, and was convinced that the bearings were shot. So, I ordered up a set of taper roller bearings, and made plans to fit them. However, I ran out of time (and patience, and humour) when attempting to get the old bearing cups out, so I just cleaned up, regreased, and refitted what I had. Since then, it’s actually been OK. I’ll still fit the taper roller bearings, but that’s now dropped to the bottom of the list. Or to whenever I have enough money and time to ask someone else to do it for me. It’s a git of a job.

Reg/Rec. Yes, the old regulator/rectifier fried itself. I’m not surprised really, as it was 20 years old, and what actually happened was that the connector block started arcing, which melted everything, and led to additional load on the reg/rec:

20180509_190357 (1)

Now, in an unbridled display of optimism, I replaced the failed 20yr old Yamaha item with a 30yr old Suzuki item, because of course, Suzuki are well known for the quality of their 1980s bike electrics… (Incidentally, I was looking at the wiring diagram for a GSX1100 the other day. The wiring there is designed to only use all three phases of the alternator when the lights are on, rather than fit a unit that could cope with running with the lights off). And this actually worked for a while, until I could get another Yamaha unit to replace it with. I know, I should have bought a lovely new MOSFET unit, but the plain fact is I don’t have the money kicking around right now, so I’m making do and mending. The new unit is soldered into the loom, rather than risking another connector meltdown. Fingers crossed, as this is the one thing that worries me for the long ride across France.

Re-pack cans. Yeah. This was absolutely necessary, and long overdue. The old packing was basically some nasty old loft insulation held in place with masking tape. Classy. A repacking with the correct size Acousta-fil matting has made the thing a lot more pleasant to be around, both from the rider’s seat and I should imagine from the side of the road too. If I was ever to stand a chance of passing the noise test up at Cadwell Park, this was always going to be necessary. I think I’d also like to apologise to anyone on the A1 over the past few months who I scared.

Tyres. Yup. When I rebuilt the bike, I put a set of ex-race Pirelli Weavemasters on there. And hated them. There was no end of grip, but really, they just didn’t feel ‘right’. I suspect they were just worn badly, as Pirelli really are a good tyre manufacturer. Not my favourite though – that accolade goes to Continental. So, last time I was on the Isle of Man, I picked up a lightly worn set of Conti RaceAttack Comp Softs. And they’ve been completely transformative. The bike turns quicker, holds a tighter line, and doesn’t kick off so badly when twatting the gas over white lines and cats eyes. Now, I’ve put a good few thousand miles on them, but there’s still enough tread for the track day up at Cadwell (and as they’re softs, no end of grip either…) but probably not enough for the ensuing few thousand kms around France. So, I have a set of SportAttack 3s on order, to fit after the trackday.

Oil + Filter. No need to go into this really. The bike needs an oil change. Motul 5000 has always worked well for me, and is nice and cheap now that its been superceded by 5100.

Brake pads. The EBC HHs on there were always a stop-gap until I could get some Bendix pads. That time has come, so I need to get these ordered and fitted to give them a chance to bed in before I get to the track.


So, that’s it really. The bike has been pretty reliable, other than the failed reg/rec. And if that’s the worst thing to worry about, well, I’m pretty chuffed. Actually, thinking about it, I also blew a headlight bulb, which is a pain in the arse, as the P30T-40 bulbs are hard to come by, expensive, and I need a spare for the trip through France. Dammit.


I’ll take bets now on my crashing at Cadwell and buggering up a perfectly good holiday plan…


[1] It’s a pretty cool shed


Flat of Angles [1] 30 March, 2018

Filed under: Motorcycling — nr @ 12:38 pm

So, things have been progressing. Without further ado:


That’s the first test run of the data logger. running at 5Hz. The eagle-eyed among you will notice there are no lean angle values. The reason for this is simple – the ADXL335 that I’m using will never ever measure a lean angle in a dynamic system with any accuracy. It’s measuring acceleration, so in a static system, you can calculate a lean angle with no problem. However once things are moving, and bouncing around, there’s going to be all sorts of accelerations in all sorts of planes, and so extrapolating a lean angle is next to impossible. Certainly for me anyway. I’m sure it can be done – just not by me. So, I’m now looking at a gyro, to go with the accelerometer, to give me lean angle. This may not be possible on the Uno that I’m using, due to the number of inputs I have to play with. But we’ll see.

Talking of the platform, if I was to do this again, I’d probably use a Mega, rather than an Uno for development. The extra serial pins would be useful to run both the GPS and a serial console for debugging. As it is, I’m flashing LEDs and dumping to the SD card when things go wrong, which is adequate for such a simple project. In fact, it’s quite good fun, and reminds me very much of my early days programming in 6502 assembler.

So, next step really, is to hook up the TPS properly (you can see it’s reading zero above – I still don’t have the voltage regulator built yet, so I daren’t plug it in) and work out a good way to mount all this to the bike. But, as a first test, I’m happy with that. It must be said, that building the map is ridiculously easy. Just load up the .csv file as a Google Fusion Table, and visualise it as a map. That’s all there is to it.

Postscript: So I hooked up the TPS:


Nothing exploded, and there’s no sign of the magic smoke. Obviously needs calibrating, and it’s a bit jittery so I may do some smoothing. But that’s that really. It all works. Just need to sort out the whether I can get the lean angle sensor working, and why Excel is stripping the hour off the timestamp in the graphs.

[1] Still can’t quite believe that there’s never going to be another Fall album.


Living by Numbers 24 March, 2018

Filed under: Motorcycling — nr @ 12:25 pm

I’ve been a bit out of sorts recently. Restless. Fidgety. Bad-tempered. At times, it’s got so bad that even tea hasn’t restored my karma, and I’ve taken to firing up the coffee machine. Yeah, it’s been bad. I put it down, mainly, to the weather really. The false start to Spring that we had a few weeks ago really got my hopes up that the seasons were changing, and then we had a couple of cold snaps which sent us right back into the depths of winter, and me back into my gloomy place.

I needed a project. So, I was sitting in my shed the other day, just looking around. On my workbench were the remnants of the fork valve conversion that I recently performed on the TRX. Sitting next to that graveyard of unwanted bits was a small pile of Raspberry Pi computers, with bits of wire hanging out of the box, leftover from when I was having a bit of a clearout a few weeks back. The first book on the end of my bookshelf, Data Science at the Command Line, grabbed my attention.

Motorbikes. Computers. Data… s’obvious, innit? Home-made datalogging. So, I did what any normal person would do. Put the kettle on, and had a cuppa. By the time I’d finished the cuppa, I realised that a Raspberry Pi was pretty unsuited to the job at hand, so I’d ordered an Arduino Uno, and a few bits of wire.

Spurred on by this, I decided to write down what I’d actually like to log, and came up with:

  • Speed
  • Throttle Position
  • Revs
  • Brakes

And that was about it really. I was starting to wonder if this was going to be a bit of a rubbish project, but, I was intrigued enough to want to put some thought into how I’d collect this data, and how to present it to the Arduino, and then, importantly, seeing that the Arduino has no real storage to speak of, how to actually log anything. This was rapidly turning into a multiple tea project.

So, first up, speed. Just take a feed from the speedo. Oh – of course, I’ve got a mechanical speedo drive. Hmmm, I could buy a GPS speedo, and see if I could hack into it to get a serial feed, or… hold on a moment… idea time! Get a GPS card for the Arduino, and use that to extrapolate speed. As a bonus, I could also map my journeys, and I love maps. Really. I spend hours looking at them. So, back to the internet, and a quick bit of googlage found a few Arduino GPS shields that also contained an SD card socket. So, two birds, one stone. Nice.

Next: Throttle position. I have a TPS on the TRX, so it should just be a case of feeding it into one of the analogue pins on the Arduino. I put this to one side for the time being, as it seemed pretty straightforward.

Revs: I thought about this for a while, and decided to put this one on hold – I need an oscilloscope to look at the feed to the rev counter to see what it’s doing, and how I’d feed that to the Arduino. I don’t have a scope, so I’ve put this idea on hold for now.

Brakes: This one took me by surprise really. I thought that a pressure transducer would be cheap and cheerful, the kind of thing that you pick up on eBay for 99p. So, I’d fit one, and again, take a feed to one of the analogue pins. This idea lasted for as long as it took me to find the price and availability. So, plan B was hatched. I’d just take a feed from the brake light circuit into one of the digital pins instead. So, I’d get an on/off indicator for the brakes – this is still useful, as at the track, I can tell how long I’m holding the brakes on for, and how soon I get on the throttle once I come off the brakes. But, a complication came up – the brake light circuit is obviously 12V, and the Arduino input is 5V. Also, vehicle electrical systems are notoriously noisy. I scratched my head, and put the kettle on, and again, fired up Google. And of course, someone has already beaten me to the whole bloody idea: – where I found this brilliantly simple circuit:


At about this time, I phoned Sol of 150bhp Katana fame, and we got chatting, and the idea of measuring lean angle was thrown into the mix. I was expecting an inclinometer to be expensive. But, I was surprised to find that an ADXL335 accelerometer can be had for under a fiver, and with a bit of trigonometry, lean angle in three axes can be calculated.

By this time, I had quite a pile of bits on my desk, and the Arduino IDE fired up on my PC. The GPS unit still hadn’t turned up, so I set about measuring lean angle, and throwing together the brake like opto-isolating circuit. I came up with this:


And, with no surprises whatsoever, it didn’t work. The lean angle was all over the place, and the brake sensor steadfastly refused to do anything. Considering its only function is to emit either a 1 or a 0, this is a pretty poor state of affairs.

I put the kettle on. The lean angle (the ADXL335 is the little square thing on the end of the long ribbon cable for those who are interested) was just me screwing up the maths. I really should have listened to my maths teacher in school, as really, it’s just A-level trigonometry – in the end, I just grabbed the code from and hacked around with it a bit. Then again, my A levels were 32 years ago, so it’s not surprising I’ve forgotten things. The brake light thingie was incompetence on my part. I shoved 12V straight into the input, without going through the resistor first. Luckily the things cost something like 18p each, and come in packs of 10. Once I’d fixed this, it was all fired up again, the code reflashed to the arduino, and all was well with the world. Next step was just to transfer the prototype brake circuit to stripboard for mounting to the bike:


I still need to cut the board to size (excellent! Angle grinder action ahead…), but that’s ready to be wrapped in heatshrink, and fitted to the bike now. Down in the bottom right hand corner of that photo you can see the GPS shield, which has now turned up. A quick bit of poking with the lovely TinyGPS library has shown that it’s giving me location data, and as a bonus, there’s a function in that library to calculate speed already. So, that saves me a job. Writing data to the SD card has also been tested, and that works OK too.

And that’s really where we are right now. Need to finish the coding to write the GPS data to the SD card, to go with the lean angle and brake status the code currently logs. Then I need to shuffle out to the garage to work out how to grab a feed from the throttle position sensor. I may have to do something with the voltage on this one – if it’s between zero and five volts from closed to fully open, I’m good, as I can just stuff that straight into an analogue pin on the Arduino. May want to see about filtering it somehow to prevent spikes. I have no clue how to do this, so any ideas will be gratefully received.

Total cost, so far, is refreshingly not very much at all. The Arduino was old stock, and I got it for about a tenner. The most expensive thing was the GPS unit, at about £20. The accelerometer was under £5. Resistors, optocouplers, and stripboard also came to under a fiver.

Next instalment should, with any luck, contain some actual ride logging data. Need to crack on with that coding. This may take some time, as I’m not a good programmer at the best of times, but I’m thoroughly enjoying diving into the Arduino IDE and learning about GPS protocols. I really should get out more.

Firstly though, I’d best put the kettle on. I’m done with coffee for a while now.


Never Understand 3 March, 2018

Filed under: Motorcycling — nr @ 12:16 pm

Blimey. Conclusive proof that people actually read this… I’ve had a request from my good mate Champ, to go into a bit more detail about how forks work, and how the emulator valves will help to make things better. This is a bit of a first for me. I’ve never been asked to explain anything (other than some rather inappropriate behaviour in my youth) before now, particularly in writing. Oh, hold on. No. Scratch that. I did have to write a letter to my headmaster explaining the incident attempting to abseil out of the library window.

So, anyway, Here goes. Firstly, the basics. What is suspension? Well, in it’s most basic form, it’s a spring that suspends the chassis of the bike from the unsprung bits (basically, the wheels and brakes really, and the solid bits that hold them in place). Those springs allow bumps in the road to move the wheels up and down, without transferring that movement directly to the rider. A spring, by itself, isn’t much good though – any forces imparted to the spring will cause the system to start oscillating. If you’ve ever ridden a C90 with clapped out shocks you already know what this feels like. You hit a bump in the road, and by the time you get to your destination, the thing has just about stopped pogoing up and down like the front row of a UK Subs gig. So, we need damping. This is basically a way to lose some of that energy by dumping it into a viscous medium. Oil, usually. Although in the case of the aforementioned C90, I think it’s some secret concoction of hamster piss and bilgewater. But, the principle is sound. For basic suspension, we need a spring, and a damping mechanism.

A spring is a spring is a spring. As long as you get one the right length, and the right spring rate (basically, how far does it move for a given amount of force), it’ll do the job. Too high a spring rate, and the suspension will be too ‘stiff’ for want of a better word. The spring won’t be able to deflect enough to absorb the bumps, and they’ll be transferred to the chassis. Too low a spring rate, and the suspension will bottom out – the spring will use all of its travel too quickly, and the suspension will hit the end of its travel. So we want something in between. As for spring length, well, that’s self explanatory really. No point in having a three metre long spring in a 30cm fork tube.

Which brings us to damping. On the TRX, this is done by forcing oil through holes, to slow things down and absorb some of the spring movement. On the compression stroke, there is no adjustment – there are a pair of 7.5mm holes through which the oil must flow. And on the rebound stroke, there is some adjustment – there are four holes of different sizes. And, of course, we can change the thickness (or weight) of the fork oil, so we can move it more quickly through the same size hole. (Think of drinking a glass of water vs. a thick shake through a straw. For the same amount of effort, you can shift a lot more water, as it’s runnier). Now, the problem with the TRX is that compression damping – if you hit a large bump in the road, the hole can’t flow the oil quickly enough to allow the spring to compress, so the force is transferred straight to the rider. If you put thinner oil in, it means the rebound damping is then so weak, that when the forks are compressed, they subsequently extend too violently, which is kind of OK when you’re upright, but if you hit a bump in a corner, the rebound action will make the front end of the bike pop up quite quickly, leading to unpleasant handling, and the possibility of ending up in a ditch.

So, what we need then, is a way to independently adjust the compression and rebound damping, over a greater range than the stock forks provide. This is where the emulator valves come in. With these installed, you can open up the compression damping holes (or just drill more, as I did), and control the flow using the sprung restriction in the valve. On the rebound side, you control the flow purely using the thickness of the oil (you can also physically drill the rebound drain hole a bit bigger in the fork internals if you run out of adjustment, but hopefully I won’t need to do that).  So, what we now have is the ability to flow enough oil to cope with large bumps, the ability to control that flow of oil on the compression stroke, and a completely separate way to control the damping on the rebound stroke. Which is exactly what we wanted. To make changes to the compression damping, we need to fish the valves out of the forks, and give the spring tensioners a twiddle. To make changes to the rebound damping, we use a different weight oil. I’ve tried to sum that up in the following table – no idea how WordPress will justify this, but let’s give it a go:

Rebound Compression Action
High High Thinner oil
High Low Thinner oil, increase compression adjuster
High OK Thinner oil, increase compression adjuster
Low High Thicker oil, reduce compression adjuster
Low Low Thicker oil
Low OK Thicker oil, reduce compression adjuster
OK High Reduce compression adjuster
OK Low Increase compression adjuster
OK OK Cup of tea

Of course, it goes without saying, that pretty much any modern bike will have a better setup than the stock TRX850. Really, anything from the 90s onwards, with upside down forks, will have this range of adjustment built in with separate damping adjustment possible

And even more of course, Racetech have a far better description of all this, complete with some nice pictures: – this description makes no mention of the rebound damping adjustment that needed to be removed in my case, but the principle is exactly the same.



Le Sacre du printemps 2 March, 2018

Filed under: Motorcycling — nr @ 12:59 pm

For pretty much as long as I’ve ridden the TRX, I’ve wanted to do something about the front suspension. The forks, somehow, contrive to be weedy, bouncy, clattery, harsh, underdamped and overdamped. All at the same time. Looking on the bright side, well, the spring rate is about right for my weight, and they do keep the front wheel pointing in the right direction, but that’s about all they really had going for them. I’m probably being a little unfair, as the roads that I ride on around here are notoriously bumpy, and even well suspended bikes are soon tied up in tankslapping knots. Just avoiding the rapidly approaching dykes can be enough to keep your hands full at times. So, I had a few days off work this week, the bike was up on stands for a bit of routine maintenance, it was the perfect time to do something about it. A lot of TRX850 owners take a fairly radical approach to this problem, by just throwing the stock setup away, and replacing it with a set of forks from a YZF750. I briefly considered this, but ruled it out on the grounds that I fancied having a crack at fitting some cartridge emulators. If they don’t work, I can always throw them away, and then fit a fancy front end from a proper bike.

So, stage one then, was to determine what to buy. Racetech have always been the standard for cartridge emulation, but there’s a long lead time, and they’re pretty expensive. Enter the YSS PD fork valve. £63 a pair, the right size, in stock, delivered. That’ll do nicely. A litre of Rock Oil suspension oil completes the shopping list. “But what about the new seals?” I hear you ask. Well, yes, that would have been prudent. But, I put new seals in there when I rebuilt the forks, and it’s perfectly feasible to fit emulators without disturbing the seals, so I left them as is.

A couple of days later, a nice parcel turned up, and the valves dropped out:


I pottered out to the shed to fit things. This would have been much easier if it wasn’t 8 degrees below freezing, but at least I have a heater in the shed. Fitting emulators consists of five steps really:

  1. Drain oil, remove springs, spacers, damping rods.
  2. Shorten internals to allow new valves to fit.
  3. Open up oil flow in damping rods.
  4. Remove old damping gubbins.
  5. Refit everything.

So, pretty straightforward then. At first glance it seems like there’s a lot of complicated things to do, but break it all down, and it’s easy enough.

Step one passed without drama. The forks were dropped out of the bike, the caps removed, and then the springs and spacers came out with the aid of the magnet on a long stick. I turned the forks upside down in a bucket, and let the oil drain out. While that was happening, the damper retaining bolts were unscrewed from the bottom of the fork legs, and the dampers fell out with a nice clonk. Everything was cleaned up, and the forks just left in the bucket to complete draining.

Step two: making sure everything fits. Well, first step I guess is to measure the thickness of the valves. Out with the calipers:


I make that about 14.5mm, give or take. It’s not that critical. Now, we can either remove that amount of material from the spring, the damper rod, or the spacer. If I had a lathe, I’d probably remove that from the top of the damper rod, as that would make step four a lot easier (more of which later). Under no circumstances would I attempt to shorten the spring. Which leads to the spacer. Transferring the dimension to the spacer is trivial:


As well as not having a lathe, I don’t have any engineers blue either, so I just used a Sharpie, so the line scribed by the caliper was more visible. A quick appointment with Mr. Hacksaw later, and the spacers were about 14.5mm shorter. Again, a lathe would have made this easier. I really should start saving up.

Step three. Where were we? Ah, yes, increasing the oil flow. As standard, the damper rods have a pretty restrictive flow, which I think is responsible for the horribly overdamped high-speed damping in stock form. So, we’re going to replace a pair of 6mm holes with six 8mm holes. I chose to go this way, rather than just opening up the existing holes, as this bit of metal supports the entire weight of the bike under heavy braking. And I know I’m famous for saying “what’s the worst that can happen?” but in this case, I don’t even want to think about that. So, let’s mark up the damper rod where the new holes are to go:


Again, no engineers blue, so the Sharpie was pressed into service. I tried to keep things as well spaced as possible, with the middle set of holes at 90 degrees to the others. A whack with the centre punch, and a bit of drilling, and we’re left with this:


Which looks a lot more meaningful. What’s important here isn’t so much the drilling, as the cleaning up and deburring afterwards. We really don’t want to leave any swarf lurking in there to rip out the seals and get stuck in the valves later, so I spent quite a bit of time filing off the burrs internally and externally, and flushing the things out with solvents and compressed air. I’m resigned to the fact that they won’t be 100% perfect, but they’re as good as I’m going to get them without some very specialist equipment.

Step four: removing the existing damping gubbins. This is the most involved aspect of the job. The first stage of this is easy enough. Pop out the circlip from the damping adjuster:


With that removed, just pop the adjuster out of the damper rod. The little spring and ball-bearing used for the detent mechanism will fly out, so be careful you’re not looking too closely. Of course, this will land in a dark corner of the shed, never to be seen again. Here be spiders. With that removed, you now need to block up the five holes left at the top of the damper rod:


As mentioned earlier, if I had a lathe, I’d simply have taken 14-15mm off the top of the damper rod, which would have removed the four small holes used by the damping adjuster detent. But I don’t, so I had to think of another way. It’s perfectly feasible to sleeve the inside of the rod, and I considered using the old adjusters to do this, but they would have needed lots of machining to remove the core of the casting, and I just don’t have access to that kind of machinery. So, I cleaned everything up as best I could, and broke out the MIG and angle grinder:


Now, it’s worth remembering that in the hands of the right person, an angle grinder can be a precision tool. Looking at the above, it’s safe to say that person isn’t me. Anyway, again, this isn’t brain surgery – it just needs to be clean, and oil tight. Again, give everything a good clean in solvent to get rid of any swarf left behind by the grinding. Also worth mentioning that I cleaned things up a bit more with a Dremel to get into all the nooks and crannies. Finally, (and this really should have been covered in step two), I chopped the adjuster rods off near the top:


This is purely to stop them clouting the new valves when everything is buttoned back together. Which brings us on to:

Step five: putting everything back. Again, give everything a good clean, then put the damper spring and little red plastic seal back on the damper rod. Drop it into the fork, and refit the retaining bolt. Prepare to say goodbye to the little valves:


Drop the valves on top of the damper rods, with the long bit of the adjuster on top. Refill with oil (I used 10 weight), and the book figure is a 130mm air gap, compessed, with no spring. Now, when pumping the forks to expel any air from the damper mechanism, chances are that you’ll push the valves up out of their seat, and they’ll land again at a funky angle. This isn’t what we want at all, so spend some time with the spring and dampers fitted, bouncing things up and down, checking that the caps will fit without undue pressure, to ensure that the valves are seated correctly.

And that’s it really. Any difference? No idea at the mo. There’s eight centimetres of snow outside, and no way I’m going for a test ride. So much for the rites of Spring.


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