nr's blog

Short Sharp Shock 9 December, 2016

Filed under: Motorcycling — nr @ 8:47 pm

Blimey. After complaining last month that not a lot was happening in TRX World other than cleaning up a lot of manky components, rather a lot has happened in a short space of time. Firstly, the engine and mounting… well, as mentioned, the lower rear mounting bolt was seized. Completely. I got the engine out by unbolting the little brackety-wotsit, but that left the problem of how to get the brackety-wotsit out of the frame. I tried everything I could think of – but in the end, the only way this came out was in about eighteen pieces, with the aid of an angle grinder. So, feeling a little despondent that I’d need to scour breakers yards for a part that I didn’t even know what to call, I went into the spares box to at least look for another engine bolt. First thing I found was a brackety-wotsit, complete with new mounting bolt… I get the feeling that one of the previous owners tried to get the same bolt out at some point, realised that it wasn’t going anywhere, so bought the necessary spares before giving up on whatever plans they had. Still, not to worry. The bottom end of the engine was delivered to Spike at Cambridge Motorcycles to have the gearbox work done – and I have to admit, that it was only when I got it out of the garage and into daylight that I realised just how filthy it was. Sorry Spike. Along with the gearbox, I also had a new camchain fitted, as there’s no way of knowing how old the existing one was. At the same time, Spike give the cylinders a good honing and a new set of rings was fitted. New gaskets all around, the the job’s done, and the engine should be good for another 20,000 or so miles, unless I louse up refitting the top end… Talking of the top end, I’ve cleaned it all up as best I can. Really, it could do with some big valves and more of Spike’s genius cleaning up and flowing the ports. Where did I put that lottery ticket?

So, engine is good, and ready to go back in. The frame was originally going to be blasted, and repainted. However, I had a change of heart. You see, this was a race bike. It’s had a hard life. And I quite like that. So, the frame was cleaned up, and the obvious rusty parts given special care and attention, and then re-painted with silver Hammerite. Oh, and the coil mounting lug that had snapped off was re-welded. All good. The swingarrm was given a good weeks worth of cleaning. I don’t think it had ever been cleaned previously. So many many hours of soaking in all sorts of nasty solvents, and brushing with wire wool, and now it’s presentable again. It’s still got dings and scratches here and there, but remember what I was saying about it being a race bike? I quite like those scars.

So, engine OK, frame done, what else do we need? Ah, wheels. Yup. Wheels. How much trouble can a wheel give me? I mean, it’s a wheel, and just goes around, right? Well, firstly, the rear wheel. I thought it was meant to be black. Honestly. It was only when I started cleaning it up that I realised that the black was in fact about 18 years of old chain lube. The wheel is actually a beautiful deep gunmetal colour. So, the process of cleaning began, and as with the swingarm, it took days of solvents and mechanical cleaning with brushes and old socks. Looking on the bright side, the chain lube had protected the finish, and the bearings were just fine and dandy. So, onto the front wheel. Oh dear. A closer inspection revealed that the light silver colour was in fact where the finish had basically fallen off after years of neglect. So, the only option really was to whip the discs off, and repaint it. Only of course, the disc bolts were as seized as the engine mounting bolt. Hours of soaking in penetrating lubricant, heating, hitting with hammers, and attacking the bolts with an impact wrench had six of the twelve out, and the other six with the sockets completely rounded out. So, out came the MIG welder, and I started welding big bolts onto the end of the disc bolts so I could at least swing at them with a big bar, and the heat of the welding also helps to loosen things. Four of them came out – one of them was so seized that it brought most of the internal thread with it. Closer inspection revealed that this bolt was bent. So some complete idiot had put it in, wondering why it was so bloody tight, but just attacking it with longer and longer bars until it wouldn’t turn any more. The other two bolts started to move, and then both stopped, seized, and snapped off inside the wheel. Bollocks. Given how badly seized they were, there was no way that they were coming out with an extractor. So, I popped along to a local engineering works to see about getting them milled out, and re-threaded. The simple answer was that no, there was no bloody way they’d do that unless I handed over a considerable sum of money. Bother. I know that the TRX is a pretty good bike at pulling wheelies, but still, I’d need a front wheel at some point, if nothing else, it will keep the MOT man happy. At this point, a wheel turned up on eBay in perfect condition, in the right colour, for fifty quid delivered. I’ve never hit the ‘Buy It Now’ button so bloody quickly.

Engine, frame, wheels, what else? Ah, yes, suspension. The shock had damped its last some time around 2001 I guess. I’m trying to think of a polite way to describe it, but the only phrase I keep coming back to is ‘completely fucked’. Obviously, I could attempt to get it rebuilt, but a nagging feeling was telling me that this was just throwing good money after bad. So I did a little research, and found out that a shock from the right year of R6 was a good match, with a little bit of work. However, while researching this, I had a note from my mate Fozzy. He’d been racing an SV650 a couple of years ago with Darvill Racing, and he thought that there was still a lovely Öhlins shock sitting on a shelf somewhere that might be worth investigating. We got chatting to Alex, the team principal, who disappeared out into his workshop, and came back with the good news that it was about the right length as far as he could tell, and would I like to try it? Well, i didn’t need asking twice. So, a few days later it turned up, and amazingly, dropped straight in. Perfect length, correct fitments top and bottom. The only thing I need to worry about is the spring rate – which I think may be a bit high for the TRX – but the only way I’ll know for sure is when I take the bike out for its shakedown tests. I can’t believe just how brilliantly this turned out – and I owe Alex a massive debt of thanks, and several Really Good cups of tea.


So now, the frame is ready to accept the newly rebuilt engine, and is sitting on some lovely new suspendery-bits. The wheels are ready to slot back in. Obvious jobs that still need doing are the fork seals and brakes. And there’s still a lot of general cleaning up and tidying as I go along, like the wiring and vacuum hoses. But we’ve definitely turned a corner.

It’s construction time again.


Germfree Adolescents 30 October, 2016

Filed under: Uncategorized — nr @ 3:30 pm

No photos for this update, mainly because I can’t remember where I put the camera, but also as there’s very little worth photographing at this stage. Hopefully once I get past the “cleaning the crap off and trying to catalogue the list of horrific bodges that need fixing” there’s going to be something worth taking a piccie of. So, first up… the head. As we saw last time out, it was in a bit of a state really, with a binding journal, and some tight clearances. While fixing that lot I also discovered that one of the exhaust studs has been snapped off at some point, and the helicoil bodge drilled off centre and at a rather jaunty angle. And, probably to mitigate the effects of an exhaust that wouldn’t seat properly any more, each exhaust port had two gaskets hammered into it. Fixing this would involve drilling out the helicoil, filling the hole with weld, and re-drilling and tapping the hole in the right place. I genuinely can’t be bothered with that, given that the rest of the head is pretty marginal. I may well look out for another head at some point in the future to see if it’s in better condition. Well, it’s unlikely to be any worse unless someone has set fire to it. For now, I’ll just re-bodge it, and see how it all runs.

The engine itself is now sitting on the floor next to the bike, ready to be handed over to the chaps at Cambridge Motorcycles for the gearbox work. Getting the engine out of the bike was one of the least enjoyable things I’ve done for several years. It should have all been a relatively simple process, but the lower rear engine mounting bolt wouldn’t shift. In the end, I was able to unbolt a little brackety-wotsit affair with the engine still in situ, and then allow the whole thing to slide forwards and out. It took three people though, and a not inconsiderable amount of tea. Once the engine was out, I could get to the bolt properly, and nothing I’ve tried so far has moved it. I’ve hit it with hammers, heated it, hit it again ,got a bigger hammer, soaked it in all sorts of nasty solvents and penetrating lubricants, heated it again, got the really big hammer, and even spent real money on an impact wrench. It’s still not moved. If I can get the engine back in the same way it came out, I think that’s what I’ll do. Last option for removal of the bolt is to weld another bolt onto the end of it, and get a big bar on there. Either that, or cut the whole thing out and try to pick up another brackety-wotsit from a breaker.

Which leads us nicely to the carbs. It’s fair to say that these carbs (Keihin FCR41s) were one of the main reasons I wanted to get my hands on this particular bike. I don’t think I’d have been tempted to swap the ZXR if it wasn’t for them. They suit the bike perfectly, and look great. Well, that’s to say they probably looked great. I couldn’t actually see them, as they had so much crud accumulated all over them. Honestly, when they came off the bike it looked like a massive ball of black tar with a couple of blue bellmouths sticking out of it. So yesterday I started to clean them up. And it took five hours of soaking in petrol, scrubbing, more soaking, running through the ultrasonic tank, scrubbing, cleaning etc. etc. But eventually they all came up clean, and it looks like all the jets are good. The throttle position sensor seems to be slightly out of alignment, but that’s something I can sort out once the carbs are back on. For now, they’re sitting on my bench looking lovely again. Now, seeing as my hand currently looks like this:


I’d like to say that all of the above work was carried out in an atmosphere of complete cleanliness and ruthless observation of hygiene protocols. Only that would be a complete lie. Luckily the stitches survived most of the work, and I only had one bloody moment when I tried clamping up some mole grips on the wayward exhaust stud. That was enough of a warning note though to make me hang up my spanners for a couple of weeks. Normal service will be resumed shortly.


Lovely Head 11 October, 2016

Filed under: Motorcycling — nr @ 11:44 am

One of the things that I knew about the TRX when I picked it up was that it needed the gearbox output shaft replacing. Now, on pretty much every other bike I’ve owned, you can get to this by simply turning the engine upside down, and removing the lower engine case. I say ‘simply’, but obviously that’s a bit involved, as it means dropping the engine out of the frame, and all that entails. But still, it’s a reasonably straightforward process. So, I picked up a second hand set of gearbox internals, and read the manual. To get to the gearbox, I needed to remove:

  1. Valve cover
  2. Cylinder head
  3. Cylinder block
  4. Pistons
  5. Clutch
  6. Starter clutch and idle reduction gear
  7. Gearchange mechanism external components
  8. Oil pumps
  9. Cam chain and guides
  10. Oil tank
  11. Oil sump
  12. Balancer shafts
  13. Water pump
  14. Starter motor

Hmm. That’s quite a list. And to get at some of those things, I need to remove other things first. So, it’s a Big Job. And while I’m OK with Big Jobs for the most part, I don’t have the necessary tools for a lot of this. So I made a decision to strip the motor down to the bottom end, and drop that off with the super chaps at Cambridge Motorcycles to swap the gearbox out, while I take a look at the top end.

So, off came the head. That’s a very glib statement for something that took several really good cups of tea and quite a lot of grunting. But there were no stuck fasteners, and other than it being a bit of a squeeze to lift the head off with the motor still in the frame, I soon had it sitting on my bench. You may ask why did I pull the head while the motor is still in the frame, given that I’m going to be dropping the motor anyway. I’m sure I’ll think of a good reason soon enough. It soon became obvious that all was not well with the head. Firstly, the clearances on the inlet for cylinder #2 were, well, basically not there. So new shims on order to fix that. More worrying though, was the fact that the inlet cam was very tight to turn. I popped the caps off, and it was soon obvious why: the cap for the #1 cylinder was binding on the shaft. Now, the preferred way to sort this is to send the whole lot away to a specialist for re-boring and honing and all sorts of expensive stuff. I just got out a scraper and some wet and dry paper. Seems to be OK now. Now, the obvious question is how the thing was still running like this – and I’m not entirely sure. There’s obvious signs that the aluminium in the seat has picked up in a couple of places and burred a little. So I’m being optimistic, and thinking that it had only just started binding when the bike was taken off the road. The alternative is that the head is so warped that when it gets pulled down onto the block it was bringing things back into alignment. I don’t really want to consider that option right now. Anyway, even if that was the case, the seat and cap still needed deburring, so I’m not desperately unhappy.

This is the first time I’ve looked inside a Yamaha five valve head. And while there’s no doubt that it’s all very clever and everything, is there really any advantage over a four valve setup? I have my doubts. Still. It’s pretty, and I took a photo, so there you are.

I know that while I’m in here I should probably replace the valves, but that’s out of budget right now, so again, I’ll clean up what’s there, put new gaskets in, and put it all back together. Now I know how simple it is to pop the head off, this is something I can work on in future.

I’d still rather be working on the TZR250 though.


Zinc Alloy and the Hidden Riders of Tomorrow 29 September, 2016

Filed under: Motorcycling — nr @ 5:00 pm

So, further to my last post, a TRX850 is now sitting in my garage where there used to be a ZXR750. And while I’m immensely happy and excited by this turn of events, it’s not all beer and skittles. So, first, the good news:


It’s a handsome devil, and no mistake. But don’t be deceived by appearances. There is a long way to go before this goes anywhere near a road. First and foremost, the gearbox output shaft is, well, shafted. So the engine needs to come out to fit a new gearbox. And while it’s out, well, I may as well have a bit of a polish around the ports. The exhausts look to be sound, but really need a lot of care and attention to get them straight and looking good again. The engine hasn’t turned over in about 7 years as far as I can make out – last MOT certificate I can find with the paperwork expired in 2009 – so that engine rebuild becomes more critical I guess.On the bright side I stuck a socket on the end of the crank and turned it through a few degrees, and it felt smooth and free, so that’s OK. The tank is completely chock-full of rust. Not sure if I’m going to deal with that chemically, or with electrolysis, or both. First I’ve got to work out what to do with the three gallons of seven year old fuel that’s in there… And this has got me worried about the carbs – they’re going to be pretty manked up I guess. Bodywork is solid, but faded. Frame is rusty. Brakes work, surprisingly. But will be completely stripped and rebuilt before attempting to actually ride anywhere. Wiring loom seems OK, but needs the alarm chopping out. Battery is flatter than a slow hedgehog. Scottoiler needs removing and throwing in the corner. Instruments need new glass (well, plastic, but you know what I mean) as what is in there is cracked and discoloured. Shock damping has long since vanished. Fork seals are leaking. There’s certainly going to be other bits & bobs too, but I’ve run out of space on the list of things to do already.

So, did I do the right thing? Swapping a clean, roadworthy ZXR750H1 for this can of worms? Well, yes, I think so. I need a project to keep me busy, and I have a bit of history with this bike, so I think it’s a good swap. Financially, there’s no question that with both bikes in their current states, the ZXR is worth more. But there’s a lot more to it than money. I have a connection with this bike going back to 1998 – digging through the history of the bike, it was raced int he BMCRC singles twins and triples class in the ’98 season. At the time, I was racing a TZR250, and we quite often shared grids with the twins. And on at least one occasion I definitely shared a track with this bike, if I believe the scrutineering stickers on the race fairing. I’d like to find out a bit more about the race history of the bike if possible. The race bodywork that it came with is carrying number 67, but of course, that’s probably changed over the years. But it’s as good a starting point as any. If you campaigned a TRX850 with BMCRC in ’98, please do get in touch. I may be rebuilding your old bike.

Postscript: after a lot of digging around, mainly by the splendid Pete Bartlett, we came to the conclusion that the owner/racer back in ’98 was Trevor Powell, from Lutterworth.


Wallop! 19 September, 2016

Filed under: Motorcycling — nr @ 4:46 pm

Back in about 2001 or so, I was instructing at a trackday up at Cadwell Park with a group of friends. One of the benefits of having such nice friends is the freedom with which bikes are shared around. “Can I have a go mister?” is normally met with a cheery smile, and a set of keys being thrown your way. For instance, this year, I spent several sessions riding a Ducati 748SP. And a TZ250. And a Classic TT spec ZXR750. Anyway, on this particular day I wasn’t actually asking around for rides, as I think I was on one of my ZXR750s – and as you may have gathered from reading this over the past couple of years, I’m rather keen on riding ZXRs. However, my friend Mike was there on his TRX850, and without being prompted, threw the keys at me, and suggested I take it for a little whizz. I accepted gratefully, as it looked like a fun way to spend 20 minutes.

Now, whenever I borrow a bike at a trackday I’m always *exceedingly* careful with it. For obvious reasons. I don’t want to be trusted with a valuable bike only to give it back in a box. And more to the point, I cannot afford to. So, whenever I borrow a bike at a trackday, I pootle around on it, avoiding the redline, and riding around corners like I’m riding on Teflon. With oil on it. And a big spiky fence around the outside. With hungry bears on top. So, I pottered out of the pitlane, and tipped into Hall Bends. And had an epiphany. By the time I got as far as Barn I had my knee on the deck, and had to rely on the services of the rev-limiter on the start/finish straight to prevent me doing something expensive. I spent the rest of the session being decidedly un-careful. And enjoying myself hugely. And when I gave the bike back to Mike, he was smiling as much as me.

“Good, innit?” he said.

“I want to buy it from you.” I replied.

And I really meant it. However, time passed, circumstances changed, things happened. Mike sold the bike on, and I lost track of it. I still wanted it. But I knew I’d never ride it again.

And then a few days ago an email popped into my inbox. The bike had survived more or less intact over the years. And was sitting in a garage just over The Fen from where I live. And the current owner would be receptive to the idea of letting it go to free up space in the garage for a running bike. There were two problems. Firstly, space. I already have two bikes, and no space in the garage for a third. Secondly, money. Money is probably the only thing I have less of than space. I needed a plan. And it didn’t take long to formulate one. The owner of the TRX wanted a running bike. I wanted some space and the TRX. So a couple of emails went back and forth, we met yesterday, and shook hands on a deal.

The ZXR750 is going to be swapped for the TRX850. That’s how much I value this bike. I should probably explain, that it’s not an ordinary TRX. It was originally built as a racebike, with Ohlins shock, blue-spot calipers, thumpy exhaust cans, and FCR41 flatslide carbs. And then it was put back on the road with all these bits still in place. And they’re all still there. The bike is in a bit of a state currently, and will need a complete strip and rebuild. But it looks to be salvageable. I know it’s a bit of a gamble swapping a perfectly roadworthy ZXR750 for what is essentially a big pile of bits. But I don’t care. That’s how much I like this bike. So, the plan is to pick it up next week, and then spend the winter in the garage making it lovely again. And next year, I’m going to go back to Cadwell Park, and give the keys to Mike for a ride. And I damn well hope he gives it a good seeing to.


Pipe & Slippers 14 June, 2016

Filed under: Motorcycling — nr @ 8:43 am

Out of all the TZRs that I’ve built & raced, one thing has remained constant – I’ve always used the stock pipes. (Well, to be honest, there’s been a common theme of mechanical mediocrity and dubious aesthetic taste, but we’ll skip over that for now). There’s been a couple of reasons for this:

  • They make pretty good midrange power.
  • They came with the bike.
  • When I started racing, they fitted into the class rules.

Of these, the second is obviously the most important, as it meant that I had no need to go out and buy new pipes. Now, while the stock pipes were OK for performance, they do weigh quite a bit (I’ll come back to that in a minute), and they won’t let the bike rev past about 10,000rpm. I’m actually OK with this rev limit though. A lot of racers will use pipes that go to 12,000 or so, which is great for performance, but engine longevity can suffer.

So, what has all this got to do with a road bike? Well, a couple of weeks ago I started looking around at my bent and scratched stock pipes, and decided I could do better than that. First thought was to give them a really good clean up and a coat of high temperature paint, and while this certainly helped them look better, I started to look around for something to replace them with. First thing that turned up was, I kid you not, a genuine set of YEC FIII kit pipes. These are vanishingly rare and lovely things. But at £800 for the pipes, and then you need the electronics, and engine and carb tuning to make the most of them, that was a bit optimistic. So I looked at a set of K2TEC pipes from Japan, which looked well priced, but information about them was scarce (for example, the manufacturer couldn’t tell me whether they were designed for road or race, and whether any other work would be needed) and besides, if they were wrong, sending them back to Japan would be a massive pain in the neck. And then I remembered back when I was more involved in the TZR scene a few years ago, a chap called Martin. He had a TDR250 which needed new pipes, so he did the only obvious thing. Taught himself how to design, hydroform, and weld pipes from scratch. These pipes were light, and designed for the road rather than the racetrack. Five minutes of searching put me in touch, and about 10 minutes after that, I’d asked him to build a set of TZR pipes for me. Well, that was easy, right? What could go wrong?

Absolutely nothing went wrong at all. A few days after placing the order, the postie turned up with a large box. And although I was meant to be working, I instantly scuttled out to the garage, and about 20 minutes of spanner twiddling later, I had this:


So, safe to say that they’ve obviously improved the looks of the bike straight away. It looks 20mph faster, even while it’s standing still. The Tyga cans were ordered separately, as I just like the look of them. Another option was to buy a set of four TZ750 cans and sell two of them, but I didn’t do that on the grounds that I’d hold on to the other two for ever just because they look nice. Oh, and remember what I was saying earlier about the stock pipes being rather heavy? They come in at about 6kgs each. The new pipes and cans are about 2ks each. So that’s 8kgs saved straight away.

At the same time all this was going on, my friend Rik posted up a programmable YPVS controller that he’d bought from a while back, but never used. I’d always had an itch to try one of these, so as well as fitting the new pipes I also nailed on the YPVS controller, set it to stock settings, and went for a little whizz. My seat-of-the-pants dyno isn’t that well calibrated, but I could tell that there wasn’t a great deal more power available. However, two things were immediately apparent. Firstly, the carburation was noticeably cleaner at about 5000rpm, but more importantly, the noise. Oh, the noise. A lovely two-stroke crackle and burble when  gently pottering, culminating in that lovely rasping noise when pushing on a bit. It sounds more like my old TZ than anything else now. So that was good. But I hadn’t touched the YPVS controller yet… I set it with a more aggressive program, and off I went again.

It’s safe to say I probably haven’t stopped smiling since. OK, so the program I chose was possibly slightly too sharp in that it seemed to leave a bit of a hole at around 6500 or so, but anything after that the thing took off like a firework rocket – one moment just a bit of fizzling and burbling, the next moment, whoooosh – gone. Brilliant fun.

And I probably should have left it there really. Just enjoying things. But on Saturday, I popped down to see the splendid chaps at Cambridge Motorcycles as they had an RC30 in for servicing, and I wanted to have a look. (As an aside, if anyone has an RC30 that they’d like to sell to me for £4.62, please do get in touch. It’s still my perfect roadbike, and would take slot #2 in the fantasy garage next to the Britten V1100). So I turned up, and Spike took one look at the new pipes, gave me the keys to the dyno room, and told me to get it run up. Now, I’ve never operated a dyno before. But what’s the worst that could happen? Well, as it happens, quite a lot. It’s pretty easy to lose a leg in a dyno room. Or, worse than that, blow up your engine. But, none of that happened. A few dyno runs later proved that the new pipes were just what I needed, with a nice smooth curve right through the revs. The programmable YPVS unit definitely made a difference, lopping 10% off the peak power when I set it to stock settings, and I had a pretty lean midrange. Time was against me, so I had to leave it there – but when I got home I raised the needles a couple of notches to try to richen up the midrange, and also took a look at the reed blocks as I suspected a small leak there. Indeed, I found a bit of old gasket stuck to the back of one of them, which maybe didn’t make any difference, but definitely wouldn’t have helped. However, all was not well in YPVS world… when I switched the ignition back on, there was nothing from the YPVS motor. Not a sausage. Sure enough, it had blown the fuse. Which was odd – I’ve never seen that before. I replaced it with another 5A fuse, but still nothing. Fearing the worst for Rik’s programmable YPVS unit, I swapped it for my standard one, and sure enough, the motor sprang into life. So I did the only decent thing, and went out for a ride. And it’s safe to say that the changes worked. It’s now beautifully smooth and clean, from 4000 all the way up. And while it’s noticeable that the top end is a little bit less frantic on the stock YPVS unit, I can live with that. For now. That’s the problem with power. It corrupts. Now I’ve seen what’s available by twiddling the powervalve timings, I want more. A taste of honey is worse than none at all.

PS. Sorry Rik.


Pump It Up 27 March, 2016

Filed under: Motorcycling — nr @ 3:35 pm

I’m always a bit nervous taking a recently rebuilt bike for it’s first MOT. Firstly, is it going to break down and leave me stranded somewhere in the middle of The Fens, within earshot of banjos playing? But, more importantly, will the MOT tester take one look at it, and laugh? I normally try to mitigate the effects of the second of these problems by taking it to the splendid chaps at Cambridge Motorcycles. I know for a fact that Spike will laugh at the fact that I’m still riding a 30yr old two-stroke that’s cobbled together from bits that that I found on eBay, and all held together by cable ties, and ancient Whitworth fasteners and plumbing fixtures. Whereas Phil will just laugh at my hair. So, that takes a lot of the uncertainty out of the process.

So, Project TZR was tentatively fired up, and ridden to Cambridge a few days back for the inaugural MOT. And it passed. It’s not perfect – there’s some play in the rear suspension (my bush is slack and floppy. Something that I guess comes with age), the tyres are down to the legal limit (already knew about this, so I have a pair of Bridgestone S20 Evos in the shed waiting to be fitted). And there was something else, which I’ve completely forgotten about now. So, I’ll get some bushes machined out of bronze to rejuvenate my bouncy bits. The standard Yamaha bits are a) no longer made, and b) made out of plastic anyway, which is why they wear out so quickly. And the tyres will be thrown onto the rims when I get the chance.

But, more importantly, how did it ride? Well, let’s get the good bits out of the way. The brakes are easily good enough to overcome any last vestiges of friction afforded by the ancient front tyre, but also have plenty of feel. Lovely. A lot of people look at TZRs with the single front disc and assume them to be underbraked. Not at all – I reckon they’ve got a near perfect balance of feel and power. The handling, despite the aging and saggy bush, is actually OK. I reckon there’s still some damping left in the shock. Which is a shock, ho ho. I didn’t want to push too hard though, as it was damp, and remember what I said about the less than grippy front tyre? The rear is worse. But still. All felt OK, and to be honest, I didn’t even notice the clonky rear.

The engine, on full throttle, is glorious. Pure two-stroke pleasure. On part throttle though… oh dear. Not quite unrideable, but not far off. Hunting and surging on a part throttle, the only way to get it through town was to constantly accelerate up to 30mph, then coast down to 20mph and start the process again. If you were caught behind me, I’m sorry. It must have been infuriating. So, where to look? first thought was needles, so I’ve ordered a new pair of needles and emulsion tubes (and a few other jets and whatnot) to refresh the carbs. Basically, every jet and gasket for both carbs, for £25 including postage. Bargain, if they’re any good. But also I invested in a leakdown tester, as I had a feeling that an air leak would also cause these kind of symptoms. Leakdown testing is a simple theory really. Whip the pipes and carbs off, plug up the resulting holes, pump some air in there and see where it leaks out from. The leakdown test kit I bought is a brilliant example of 3D printing. Super, and it just fits perfectly. So, I plugged everything up, and started pumping with an old bicycle pump (you don’t want any more than about 6PSI). Normally, you want the cases to hold 6PSI for 6 minutes. Mine were leaking air faster than I could get it in there. This was easy to find:

P1050861_arrow Those two red arrows point to splits in the carb rubbers. I think I know what’s happened – someone has used that balance pipe to pick the engine up before. I’ve done it myself on one of my old racebike engines, and had exactly the same splits appear. I don’t really want to buy new carb rubbers, as they’re expensive, and very hard to find. So, I ran some cyanoacrylate glue into the split firstly, as it’s good at that kind of thing. I then used some Loctite sealant which is more flexible to cover the split. A couple of days later I retested, and it’s now holding pressure.

So, still a few things to do, like the tyres and rear bushes. But more importantly, give it another whizz up the road to see if the part throttle fuelling has improved. I’ll wait until the carb jet kits turn up, and do that while I’ve got the carbs off. Then I’ll put it all back together, and go and make some smoke around The Fens. And those banjo players will have their work cut out to keep up.

In other news, I’ve been helping Sol put together his project Katana. This is really the antithesis of the TZR, being a big bruising fourstroke. Good fun though – pop over to for a look. It’s going to be brilliant when it’s done.


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