Pull start and bearings

First, I have a ton of miles on my engine. It's been good to me. The first summer I had it, I killed the magneto side bearing. I replaced it with a quality bearing, and never looked back. I recently added a pullstarter, the kind with the arms on the part that mounts to the crank. I love it, then my bearing fails within 100 miles. Could be a coincidence I guess, with the many miles and my habits of riding hard.

Anyone had any balance issues or bearing failures after pullstarter install?
I just bought a new engine and I'd like to keep the pullstarter, but not if it's a killer.
The "other" design pullstarter seems like it might be nicer to bearings as the arms are on the recoil side, so the magneto side is just solid and more easily balanced.
I'd like to hear if anyone else has suffered a similar fate.

The good news is I probably will end up with a better engine to start with now.
Looking forward to thousands of more miles.

Unnecessary pic, since everyone loves pics. Yes it has had a 49cc head for the last 500 miles or so.

Agreen said:

Maybe the cup is out of balance? You can try to test that by using one of those lawnmower blade balancing rigs or maybe make something similar. Just some way of telling if one side is heavier than the other. Then, like balancing a turbocharger, grind off some of the metal on the heavy spots to balance it out.

Otherwise, it may just have been another bad bearing. It's probably not a lubrication issue since it's only been the one bearing that has failed... twice. It may not even be an issue with the pull start. Maybe the crank isn't true, or the case isn't aligned.

Whatever you find, please update this thread. I'm intrigued now. I have a pull start and centrifugal clutch, so if that leads to premature bearing failure I'd like to know!

Click to expand...

It's a good possibility my crank is imperfect. It is an older bolt on weight crank. Somewhere I have one of those blade balance things, I usually just use a nail in a vice so it is at the bottom of a toolbox somewhere.
Do you use the pullstarter with the fingers on the crank cup or the one with the fingers on the pullstart end?
I have both types but got them used in a box full of stuff some years ago at a garage sale. Never tried the latter one as it had a recoil problem from previous owner.
I'll let you know what I find.