richty250e Posted May 11, 2009 Report Share Posted May 11, 2009 Dear All, A bit of a request for help here. I have just purchased a standard TY250E (493-300925) and am in the process of a complete strip and rebuild of the whole bike. All went well with the strip of the engine with just one item 'missing' and there is a contradiction between the repair manual I have and the on-line parts fiche I have looked at. So here's the problem: In the workshop manual it says to install a shim on to the primary drive side of the crank before installing it into the crankcase half (So the shim fits between the crank flywheel and the main bearing inner race). But when I look at the parts fiche it shows the shim fitted on the outside of the main bearing so that it fits between the main bearing and the primary gear. When I stripped the engine there was no shim fitted at all. So....does anyone know the correct position for the shim? All help and suggestions gratefully received. cheers Richard Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 11, 2009 Author Report Share Posted May 11, 2009 (edited) As an additional bit of information you can see the two different scenarios on the parts fiche at http://www.cmsnl.com/yamaha-ty250-trials_model16818/ On the 250A model the shim is on the 'inside' of the main bearing, on the 250C and D model it has moved to the 'outside' of the main bearing. My best guess here is that the early version of the fiche had an error which was corrected on the later versions, but I would still like to hear from any TY250 motor experts out there if this is indeed the case. thanks in advance! Richard Edited May 11, 2009 by richTY250E Quote Link to comment Share on other sites More sharing options...
tony27 Posted May 13, 2009 Report Share Posted May 13, 2009 (edited) Just had a look in the reprint B model manual & it says place shim on left side of crankshaft then install crankshaft into left case. That would mean between bearing & crankshaft which is the logical place for it because you wouldn"t normally worry about accurate bearing to seal spacing. Hope that clears things up Edited May 13, 2009 by tony27 Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 13, 2009 Author Report Share Posted May 13, 2009 (edited) Thanks for the reply Tony. It sounds like you have the same manual (TY250B by Cycleserv Publications) as me. The problem for me was that the left side case (as per the manual) is the magneto side, but in the parts fiche for the TY250B the shim is shown on the primary gear side. The fact that I didn't have any shim fitted at all doesn't help. I also looked at the DT250 parts fiche and that doesn't have any shim fitted. The shim appears to be a TY specific part and was never fitted on any model year of the DT. From what I can see the shim would control axial main bearing float/nip if fitted on the inside, and primary gear alignment with the clutch basket gear if fitted on the outside. From an engineering standpoint I would be surprised to see a shim fitted on the inside of the main bearing for three reasons:1, it would increase the stress on the crank. 2, the crank has a tight tolerance given for width during rebuild. 3, I've never come across any other crank that uses a shim in that position. The problem I have is that I write repair manuals for a living (on cars though) so I know that no one is infallible and this is an easy area to make a mistake about when it comes to writing the process down in a book, or even producing the parts fiche drawings. Maybe the only solution is to bolt the empty cases together and measure the width between the main bearing housings and compare that to the width of the crank with the main bearings fitted without a shim. I guess if the difference is in the range of the shim sizes 0.3 - 0.5mm then we will have a definitive answer. This whole question might be academic anyway as the shims are no longer available and I was quoted Edited May 13, 2009 by richTY250E Quote Link to comment Share on other sites More sharing options...
stork955 Posted May 13, 2009 Report Share Posted May 13, 2009 Gday, just to add fuel to the fire... The DT's have a different crank assy. so that may have some bearing (no pun intended). It does make some sense to shim the primary drive for alignment but I cant remember my A engine having anything there. Probably not much help... Cheers, Stork Quote Link to comment Share on other sites More sharing options...
tony27 Posted May 13, 2009 Report Share Posted May 13, 2009 Definately same book, was only 1 I could find available If you want the opinion of a ty expert try feetupfun, he is a wealth of knowledge of these bikes in australia & gave me some insights into how they changed through the years. Unfortunately I haven't had time to strip my motor yet as have 3 day event at end of month to finsh bike for & still need to make new header as massive hole blown in it isn't repairable then have airbox to make. Strip of motor will be in next couple of months if time can be found. My comments on shim placement come from my job & reading of the different thicknesses listed on csmnl.com, if you really want to try for shims perhaps look at cycle-parts.com as they listed a couple of things tonight that I hadn't been able to find anywhere. Part number needs to be entered like this 322-24748-00-00 to work Worth a try Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 13, 2009 Author Report Share Posted May 13, 2009 Thanks for that Stork, the differences between TY and DT parts are quite vague. Do you know if the DT piston works in the TY? Well I did a quick measure up of the crank and cases and it appears that there is about 1.5mm axial preload on the main bearings with no shim fitted. Sounds a lot but when you take into account the different thermal expansion of the aluminium alloy case and the steel crank then it would be less when it's at running temperature. The main bearings are C3 spec so have extra clearances when cold so that also figures into the amount of preload needed. One other thing that crossed my mind was the fact that the TY magneto rotor has the extra weight, so maybe the Yamaha boffins decided to increase the preload to control the extra crank whip on the TY motors. Still doesn't account for the change in the parts fiche diagram though! Quote Link to comment Share on other sites More sharing options...
alan_nc Posted May 13, 2009 Report Share Posted May 13, 2009 Dt piston does fit in a TY (ports should be the same but do check). You will need to grind the corner (if thats the right word) of the skirt to clear the crank. On your shim discussion: Doesn't the book say "if needed" by the shim? Lord knows how you know if it's needed. Alan Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 13, 2009 Author Report Share Posted May 13, 2009 Hi Tony, thanks for that tip about cycle-parts.com. They do have the shim listed for $4.99 but the minimum order is $75! Will have to wait until I need another expensive item to combine orders I think. In the meantime will try to contact feetupfun for his view. If your looking for a long term fix for that header there is a stainless steel one available now at Sammy Miller Products. cheers Rich Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 13, 2009 Author Report Share Posted May 13, 2009 Hi Alan, No - manual just says to "fit the shim". No description of how to calculate shim thickness needed etc. Thanks for the DT piston info. I need a +1.0 piston and genuine TY pistons are very very rare in that size with only cheap aftermarket kits (dubious quality) or Wiseco ($$$$) to choose from. I'll keep a look out for a genuine DT one now I know they will work with a little 'machining'. cheers Rich Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 13, 2009 Author Report Share Posted May 13, 2009 Just had a chat with John Cane whilst ordering some frame parts and it seems that not all TY engines came with the shim and the ones he has built without one worked fine. So there we have it, if you have one in your engine put it back in when you rebuild. if there isn't one don't worry about it. Just goes to prove you can't always trust the manual/parts fiche and there's no substitute for hands on experience. Thanks all for the replies. Rich Quote Link to comment Share on other sites More sharing options...
stork955 Posted May 13, 2009 Report Share Posted May 13, 2009 Gday, I run a DT Wiseco in my A, with no modification. It goes well. I'm a bit worried about the preload you have measured across the mains - ball brgs. will not tolerate any axial thrust at all, and there should be no preload on them at all either. Ive not yet seen any ball roller main with preload (and I've built the odd few engines over the years...) It might pay to recheck your measurements there as 1.5 mm is a lot, even if there was meant to be preload there. You should see if anything a small amount of freeplay, like a thou or so. HTH, Cheers, Stork Quote Link to comment Share on other sites More sharing options...
kevin j Posted May 13, 2009 Report Share Posted May 13, 2009 maybe related: I have a GG 200 with noise. Changed piston, top end, mains, big end is fine. Eventually figured out the crank has axial play in the main bearings and walks left and right on the helical gear spiral as it goes from driving (combustion) to resisting (compression). I have .014 inches of play. So I have to split and take that out with a shim between bearing and crank, or between bearing outer race and casing. Anyway, I say that as I suspect the shim is to take out axial play. Does the 250 have helical gears, or just straight cut? I doubt it is related to aligning the gear drive, as a few thou either way would not matter there. Do you really have 1.5 'MM' of preload, or 1.5 '.001 of inch' ? 1.5 mm is 1/16 inch. That seems totally impossible without destroying the bearings........ If you do have preload of any amount, you may need to increase the gasket thickness between case halves (assuming vertical split) Quote Link to comment Share on other sites More sharing options...
richty250e Posted May 14, 2009 Author Report Share Posted May 14, 2009 (edited) Hi Kevin, Stork The TY250 has a helical primary gear set which will put an axial thrust on the crank main bearings during drive/overun same as the GG. The bearings appear to be the deep groove type so they are designed to cope with some axial thrust. I took all the measurements with a metric vernier caliper/depth gauge so it is all metric I'm afraid. The cases are vertically split and do not have a paper gasket fitted, they are just sealed with yamabond. I will recheck my measurements again over the weekend with better equipment and see what the verdict is. Edited May 14, 2009 by richTY250E Quote Link to comment Share on other sites More sharing options...
tony27 Posted May 14, 2009 Report Share Posted May 14, 2009 Hi Rich I know of the millers header as bought a seat off them last month, freight was 2/3 cost of the seat so would want to make future order larger to compensate. Other thing is still means that I'd still have to weld to centre section/muffler Back to shim, never seen inside 1 of so can't be sure on how they look. Is the shim diameter the same as the crankshaft on the inside, if so then it would have to go between crankshaft & bearing otherwise it would shield the bearing from proper oiling Would have to agree with John on if there is no shim then don't worry, shouldn't be any real preload on bearings as that will lead to premature failure. Quote Link to comment Share on other sites More sharing options...
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