thedktor

Well for various reasons I still have a 349 engine in many pieces after all this time, but it's now come to the front of the queue yay! But I have no idea where to start with the gearbox shims, any clues? Do I centre the shafts or is one side the "reference" and you shim the opposite side to take out the play, or what? And should I assemble in the right case? I recall reading that somewhere. Thanks for any pointers.

Hi dixie, yes I realised you were talking 4-st and should have said "here's a 2-st, just for interest". You do get a slight smell from an open breather pipe on a 4-st, but the general consensus does seem to be that modern oils are much better, so I'll leave it there

This little PW-50 auto-lube 2-st was run on Castrol R. It gummed up the rings and made a right mess!

I had one! Well its a "Series 2" apparently, built around 1974. The pic is about 1979. Too long ago/too young to give a full review, but it was very torquey and would grunt its way up pretty much anything in pretty much any gear! It was around this year of manufacture that the gear-change swapped right to left, worth bearing in mind if you find one.

OK thanks feetup. Any tips for how to actually do this then as obviously the bearings are not free to float so will need some "persuasion" to move and find the right position. Cheers, Steve

OK…. So any clues then?! I have rebuilt quite a few engines but none have this shimming method. Here’s where the shims go: So looks like they hold the main bearings to prevent any creep sideways/outwards as the engine temperature cycles. Which would suggest…. That the crank bearings need to be fitted with zero clearance against the crank. Or???

Not been on here a while, but some may remember my trials and tribulations trying to get this old bike back up and running: http://www.trialscen...-gears-damaged/ http://www.trialscen...y-gear-removal/ http://www.trialscen...9-crank-damage/ …and some more… Anyway, the engine is ON THE BENCH with a genuine intention to put all the many bits back together, and I can’t recall where these things go: Well, I’m pretty sure they go between the main bearings and the crankshaft seal carriers, can anyone confirm? And if so, why??! But what puzzles me is that there at least two different thicknesses of these shim things and I’ve no idea what I’m “shimming”. Note that the picture is all the shims from two engines….. Thanks for any pointers - Steve

Hello Ben, Great job you've done there - I'm in the process of doing my 349 but focusing on the engine which has needed a complete rebuild! May I ask where you got the de-compressor from? I also went to order one just as the price jumped, so didn't... Cheers Steve PS sorry all to resurrect an old thread.

Strip and check the carb over: All good, but its so small! Fitted: Threaded ring attaches the exhaust: And just one screw supports the whole thing! Tasty aftermarket footpegs and rear brake lever go back on: Fill with oil and she fires up, smooth as you like What a little beauty

It would appear I didn't post the successful rebuild of our TY80 engine after some problems discovered, so here it is: Just to recap, a year ago we acquired a TY80 that had a recent rebuild but suffered from a gear-change problem – up changes fine but down changes very unreliable. It also rattled more than I would have expected from a rebuilt engine… So easy job first and check the clutch mechanism and general condition under the LH case: All good, so take off the RH case and clutch to check the gear-change mechanism: Note the fantastic homemade clutch holding tool that came with the bike. The gear-change mechanism has nothing obviously wrong but I notice the selector drum is free to rotate instead of clicking into place with each gear. Hmm, that’s not right but where is the indent spring thingy?? The other end of the drum, deep inside the engine…. Oh dear, but wait! The indent spring and pin bolt on from the outside of the engine and off it comes easy-peasy! And the pin had jammed in, so loosened it off, put it back, and the gear change perfect. So very pleased with that, until……… I look at the clutch primary-drive gear: A new clutch is £200! But soon find one on ebay for much less. In the meantime I’m checking the engine over and notice the crank is completely out of true on both sides!! And hence the mashed gears… Engine comes out, and cases split, all quite simple on this little bike. Crank goes off to get straightened, and declared fit to use, and in the meantime pop in some new main bearings in case the wobbly crank damaged them. All ready for reassembly: Note what great condition the innards are in for a 30+ year old bike. Cases back together, no gasket so green Hermetite used – hope it’s the right stuff! Back in the frame and do up the primary nut: Kick-start and gear-change mech fitted and tested: New s/h clutch cleaned up and ready for oiling as it goes on: Torquing up the clutch nut: Stator plate goes back on, and it should run better now the point’s cam is running true! Flywheel, and using my new holding tool The horrible clutch-release mechanism, which I’m sure was on my Fizzy as well: Greased up and put back in the magneto cover. Then piston oiled up for fitting: Ready for the cylinder: Torque the cylinder/head nuts: Check for a spark: Yes, all good so far! cont....

I have had several and still got one tidy one. They are not very powerful I must say, but with a light rider they are very capable, and WILL pull from low revs. I am 11 stone and struggle to get up anything without lots of revs in 1st gear, while my younger son at around 6st has no problems and can use 2nd gear on quite steep stuff. In my experience poor running is nearly always the pilot circuit blocked up, as the jets are so tiny it takes very little to block 'em, worth one more look I would suggest. The points have never given any problem to us, but obviously if worn or not gapped correctly it won't help. Also they will still run fine even when the piston/rings/bore are completely worn out, but low down power will suffer.... Oh, gearing too, 12/41 is standard (will check) but a 11t front will help lots. - Steve

As it happens no-one has the

Ah, yes my engine numbers starts 4AJ so pinky it is - happy with that. Agree about the tank stickers, no point spending 20-30 quid if they won't stay on, which they won't as we know. Oh well, I bought it to ride not put on the mantelpiece

OK lots of opinions, slightly confusing but all on the same line I guess! What does this mean though??? :

Thanks for the replies, food for thought. Bit of a dilemma about the big-bore kit as I will be letting my boys loose on the bike so need the power nice and soft, whereas I LOVED the power on my Gas Gas 300 txt pro that unfortunately had to go when I lost my job a while back. Point being that maybe throwing lots of money at this bike is not the right thing to do, when, in an ideal world, I would like a modern w/c bike again once finances improve, and the boys can use the TY until they are old enough to buy their own!! Saying that, I need to ride the bike properly a few times and see how it performs, I might be surprised. But the gasser

Thanks for the comments, will try it as is and see how it goes. Will have to experiment with the spring I guess... Going to order up a new cable anyway as the one here is shot, how about this?: http://www.tytrials.co.uk/trailandtrialsuk/prod_43349--13-Venhill-Clutch-Cable-TY250-amp-TY350-Mono.html

Thanks for the replies, I guessed that the seat cover is a home-made thing, but its been done neatly so may as well leave it on for now

OK, but this is exactly the symptoms I get with a blocked pilot [on a TY80], so I would check this first, and then move onto the more serious stuff.....

The engine on this TY250 is well-worn, with a good .3mm piston to bore clearance at its worst point, so a rebore needed! But am curious if this is the original, Yamaha, piston. It measures up as standard size, just under 68mm so plenty of rebore options left. The big-end is also on its last legs so need to start saving, but in the meantime I

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Hi all, Just picked up a TY250 mono, and have some questions that I would appreciate your help on. The bike is all complete, I just stripped it down to bring it home: front disk, blue forks and the frame number suggests its a

Yup exactly what I was going to say - I have several TY80's and the pilot jets are forever blocking as they are soooo small and the tiniest bit of rust/dirt from the tank blocks em good and proper....

While I source a clutch I put everything back together loosely while I concentrate on another bike. I had some suspicions why the cog had shredded its teeth but was quite shocked when I discovered the truth. The crank end is several millimetres out of true!!! On both sides, it

Thanks for the reply feetupfun, good info. I guess these marks should line up: Was thinking I need to get the butchered screw off first but the adjustment is the other end of the mechanism of course.... Alan

Now resolved, see this thread: http://www.trialscentral.com/forums/index....showtopic=30510