Rebuilding

[Gikki44]

Started tear down of the motor for a rebuild. I came to the conclusion to do this because i was pretty sure the crank seals were shot. Got everything off down to the crankcase. The right side cylinder which was smoking badly has a good amount of gearcase oil in the piping all the way through. Im guessing this is a sure sign that the crank seal was bad. Correct? Also the compression on that cylinder was only around 105 but the rings and piston look to be in good shape. Im gonna measure the cylinders tomorrow at work. I actually work in a machine shop so it'll come in handy. What else would be a sign of the low compression in that cylinder. I am also wondering if from this point with the engine still bolted to the frame can i split the cases and leave the bottom in to change the crank seals. I mean without removing the front sprocket, flywheel and all that.

[Gikki44]

Anybody?

[Larry's Shee]

Don't think it would hurt , only draw back is you would'nt be able to flush case if there's any gunk. Make sure bike is clean so nothing falls down into case - that would be drawback of doing it this way. Mic piston and bore top , middle , bottom , front to back , side to side. will give you out of round and taper. If you are satisfied it's within service limits ,hone and new rings.

[Gikki44]

Checked all areas of both cylinders today. All within .002. Should be good with that. Gonna order new rings and change out the seals. If oil is leaking out the right cylinder would just changing the crank seal on that side fix that problem? I know both should be changed, just wondering? Can the flywheel, stator and front sprocket be left on to change the seal if i just do the clutch {right side}? If the bearing is bad on that side is that an easy removal? Sorry for throwing all the questions out its just my first time rippin this motor down and its nice to have advice from people who have done it quite a few times. haha.

[Larry's Shee]

What was I thinking , I 'M SOFA KING WE TODD DID !! You have to pull the engine because the motor mounts. Have to pull flwheel to split cases. And clutch. After re-reading your post , rings on right piston might be stuck /gummed up from extra oil. .002 sounds good for out of round/taper , hows pistons and clearance? Crank seals come in pairs. Only had one 'shee engine down , but have done lots of motorcycles.

[Vintage Smoke]

Seriously...removing the engine will take you an extra 1/2 hour tops....BUT....it will probably save you 2 or more hours of extra time to try and do the job with the cases in the frame. The way i look at it if you are going far enough to do crank seals you should tear it completely down. In other words if done right it should be quite some time before you have to do it again. You will want to completely clean the cases of all old grunge, really clean any old yamabond off of the mating surfaces of the case halves, and generally clean and inspect all the parts before reassembling. If you are not 100% sure of the history and time on the motor I would go through the tranny as well.

 

Bottom line....it would suck to go as far as replacing crank seals, which involves splitting the cases any way, to only have some part (bearing, seal, gear, whatever) fail shortly after you get it back up and running. Especially when you knew you just had it all apart and could have done it right.

 

Be careful though...it can snowball!! The last one I did wound up with me bead blasting and painting the cases, etc, etc, etc.

[Gikki44]

Thanks for the info guys. Yea i noticed tonight that i would have to remove all that anyway so its all comin out, haha. I actually didnt find what i was expecting. There is no gearcase oil under the piston. There is oil but it is the premix oil only. There is quite a bit of oil/gas under it but im certain its premix. Now the compression in that cylinder was only 105 but why would it be smoking grayish blue smoke out that cylinder if it was just sucking down the premix. The top of that piston is also quite black like carbon build up. i dont think that crank seal is bad? Im freakin lost, now im thinkin i just tore it down for nothing. Also i cannot pull the shift lever out from the casing, i removed the bolt and holding piece but it just slides up a 1/4 inch or so and wont come out.

[Gikki44]

Just found out the problem. The dumbass who had it before me put the crank seal on the right side in backwards. So he claims he never had any problems but he's obviously full of shit!!