metal pin of the big flywheel broke

[LoWang]

Hi there.
the metal pin of the big flywheel on my 406c broke. impossible to kick or to ride now.

I manage to take all things out. I think have to smooth the inner surface of the flywheel wich has been used by friction with metal parts.
Also have to find a strong metal pin to fit there and maybe find something to make the flywheel fit stronger to the shaft.

Does somone know that problem? is it easy to repair?

I am a bit disapointed because it happened after only a few km... I thought I should give up but maybe i can fix it and go on, with help of god ^^

[albertaphil]

LoWang, it appears that your metal key sheared off. The flywheel appears to be okay, but I can't tell from the picture of the crankshafte whether the keyway broke out or whether that is just some parts of the old key stuck in the slot. Try to clean the keyway slot out on your crankshaft. If the keyway is broken out, I don't think that it would be a big deal for a machine shop to weld a bit on the keyway and machine it out to accept a new key. If the keyway isn't damaged, (or not damaged much) then just about any hardware store will sell you a key that will fit...just put your flywheel back on with a new bolt and make sure that it is tight. Good luck...!

Philip

[bubby-joe]

If the original key is an alloy make sure you use an alloy key to replace it with... there meant to fail to prevent crankshaft damage.
Common cause of shear pin/woodruff key failure:
1 rapid stop of flywheel (same as lawnmower blade which is part of the flywheel weight)
2 backfiring
3 loose flywheel nut

To remove the piece in the flywheel use a small pin punch and tap the inner end down into the flywheel the front end should rise up enough to remove the piece with side cutters or dykes.

The flywheel itself is a little harder to fix and will require you to hand file the slot a little deeper and square up the outside of the groove. It is possible to use a larger woodruff key and reshape the bottom to fit in the flywheel, just make sure the larger woodruff key fits tight into the flywheel, most are 1/8th or 3/16th

See the attached drawing don't go nuts on the flywheel just make it square

trial fit should go together without binding, binding will crack the flywheel (VERY BAD)

Make sure to use the proper TORQUE settings for the flywheel nut...

HOPE THIS HELPS A LITTLE.....

[LoWang]

I managed to fix it. without metal pin.

I had to work on the flywheel and the srew that maintain it (for harder maintain).

now seems to be ok, dont move anymore, starting good, running good.