After several years delay (!), I finally completed my sidelined top-end rebuild. All new parts (Wossner piston kit), all machine work sent out to a first-class machinist, 1mm over bore, new valves, cam sprockets, cam chain, etc. Set cam timing meticulously. Before reassembly, I checked the big-end side clearance in accordance with the service manual, and it was well within spec. I didn't have a dial gauge to check the small-end free play, but it didn't seem significant (the spec is almost 1mm, which I thought would seem very noticeable).
Unfortunately, I had a pronounced rattle after reassembly. Double-checked cam timing and other obvious stuff, and everything was spot on. Today I took it all apart and borrowed a dial gauge to measure the small-end free play, and it was almost 2mm. Ouch. So this appears to be the source of my problem, and it looks like I'm going to have to replace the entire crankshaft assembly.
Question for the assembled wisdom: What else do I need to replace while I've got the cases split, other than the two crank bearings, and the oil seal (and obviously all the gaskets)?
You don't have to renew the entire crankshaft. The conrod, bearing, crankpin and side thrust washers are available, but you will need a good machineshop to separate and rebuild it.
There may be other bearings you want to replace while you're in there, but you don't know 'till you see/feel them, and there's a good chance they'll be fine. Other than that, yes, just head and base gasket, clutch and stator cover gaskets and some good quality flange sealant for the crankcase joint.
That's helpful feedback, thanks. I looked at the possibility of doing the repair a-la-carte, but at least here in the US it will be substantially less expensive to simply a buy a new crankshaft assembly ($340 and widely available) than to buy the individual parts and pay for the machinist work.
the crank assembly sounds like the way to go for that price. just check the bearings when you have the cases split, i found the crank bearings OK but fitted new bearings in the Grear box (got them from a local bearing shop) , The best part of the Wosner piston is it's a bit bigger but a lot lighter allowing the engine to rev a bit easier.\
overall, a pretty easy job, doesn't take long but well worth taking your time with each step and only doing it once. (Tip if you don't have a fly wheel puller the rear axle does the job ( I took the axle to the local shop and got a bolt with the same thread and used it. Also warming the cases helps with getting the bearings out. as mentioned, a good sealant for the cases ext is a great investment. ( the manual says to put the cases together dry but i recon a bit of sealant is the wat to go )
Thanks for those tips. I do have the correct flywheel puller and case-splitter, and was planning on using Yamabond for the case reassembly. I've already ordered the All-Balls crank bearing kit (I've had good luck with their stuff, and it's less than half the price of the OEM bearings a la carte), but I'll have a look at the gearbox bearings when I have things apart.
Do you know if any/all of the bearings are available off the shelf? More work than an All Balls kit but it may save some extra coin.
On that, where are the All Balls bearings actually made? If it's China, I'd go the extra to avoid them. Sounds prejudiced but, I've heard a number of complaints of name brand bearings, made in China, that have failed.
That's like buying stuff from ebay/amazon etal. Some swear by it, others will run a mile.
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In the Riverina.
'73 RD250, '80 XS1100, '81 RD373LC, '96 Tiger 900/sidecar, '02 TTR250, and another XS11 - this time a chain drive Period 5 race bike that may be ready to race eventually.
'73 RD250, '80 XS1100, '81 RD373LC, '96 Tiger 900/sidecar, '02 TTR250, and another XS11 - this time a chain drive Period 5 race bike that may be ready to race eventually.
