Before installing a new top end on my 73 'Piner, I'd thought I would flush out the crankcase with paint thinner followed by a pre-mix chaser. A few seconds after filling the crankcase up I noticed the fluid leaking out from behind the ignition. I thought that shouldn't happen unless I have a major seal problem. The bike didn't exhibit what I would call a lean condition typical of a leaking seal on the ignition prior to taking the top end apart. A seal is all I can think of that would cause this or am I missing something else [?]
Pete Petrick
175 Jackpiner
Slow but Good
Could be a crack or small hole in the case. Pull the ignition to expose all the area around the seal. Fill the crank case again, and then use a gentle stream of compressed air slowly around the area to see if you can get air bubbles to come up in the crank case. If it is leaking at the seals, you should be able to see that also if it runs outside the case. If it's a pin hole or a crack that might not be too bad, JB Weld will be you best bet for a quick repair. If it is the seal,you know the answer to that! I have never tried it, but I have heard of guys changing the dry side seal by running a sheet metal screw into the body of the seal, then use a slide hammer device to pull the seal. Replacing the seal is done with a proper size piece of pipe that will be long enough to slip over the end of the crank, and gently tap the seal into place.
Good luck with it,
Dan McEntee
You can remove the ignition and seal plate to examine the area. While there, install a new seal plate gasket, crank seal and tighten down the plate. Reinstall the ignition, set timing and there you go! Bob's your uncle:)
Will do, I hope it is a bad crank seal!
Pete Petrick
175 Jackpiner
Slow but Good
Thanks guys. I removed the ignition and confirmed a bad seal (pre-mix ran right past it). The crank doesn't have any significant play that I could detect by applying up/down pressure to it with my hand. The seal condition wasn't what I quite expected as a portion of the inner part of the seal definitely showed signs of wear that I could easily see & feel with my finger but, then again I haven't replaced many seals. Is this much obvious wear typical of a bad seal? Personally I'm surprised the motor didn't show more signs of an air leak.
Pete Petrick
175 Jackpiner
Slow but Good
Just an idea but your paint thinner could have swollen the seal. Neopreme and even Viton do not tolerate all chemicals.
Ted
Quotequote:Originally posted by t20sl
Just an idea but your paint thinner could have swollen the seal. Neopreme and even Viton do not tolerate all chemicals.
Ted
I suppose but I'll bet there wasn't 3 minutes between the thinner and pre-mix chaser. By the time I came back with the pre-mix I had a puddle of thinner on the floor.
Pete Petrick
175 Jackpiner
Slow but Good