OK, so i fitted new woodruff key and guess what? it broke again,lucky enough i ordered 2 so i tried again making sure everything was tite but it went again,a little frustrated now...Should i have fitted a new washer aswell,cause on inspection the washer has groves on both sides,i gather this is stop nut coming loss,any idea's or tips are more than welcomes... Thanks...

Edited February 16, 200620 yr by beta rev 3, 01

happens alot on old montesa's.

i was told to lap on the flywheel with grinding paste, clean it up then put back together,

but a new washer will def. help if you want to try that first

If this has happened twice I would suggest that the problem, although not helped by your worn washer, is more likely to be that the flywheel is not tight. The torque spec if extremely high on this nut. And although it's not the ideal way to tighten this nut I always tighten the flywheel with an impact wrench.

I'd agree with the loose flywheel theory. When I repaired mine recently I was surprised to find that the flywheel nut came off really easily and I'm sure that it was this that caused the key to break.

Torque wrench is undoubtedly the best way to ensure that the nut is tight enough but if like me you don't have one to hand, put the bike in gear, hold the rear brake on and a few sharp whacks on the socket wrench with a rubber mallet should be about right. Certainly not the recommended method but it's always worked for me.

Dose anyone no where i can get new woodruff key before Sat in the Surrey/West Sussex area.... Stevens trial said the best way to tighten nut is with air power socket,so when i get my new key its off to quick fit.

No idea about Betas but reading what you have in your previous posts it sounds as if the taper is not matching very well from flywheel to crank.

The Woodruff key is only there to LOCATE the flywheel, not to stop it turning.

I would try lapping the flywheel on to the crank with fine grinding paste - it should not take much work - if you are unsure what to do speak to a friend who messes around with old bikes or old engines, they will know the procedure.. Once you have a uniform surface clean off both crank and flywheel THOROUGHLY and then refit key and flywheel.

no, no no.....no lapping with grinding paste please!

you will observe that the fitment of the flywheel to crank without tightening the nut is somewhat sloppy ie. several degrees of slop/rotation in either direction. when you tighten the nut you need to ensure the flywheel is rotated anti-clockwise and apply a little pressure to the kickstart to spin crank clockwise. this will eliminate the slop and set the timing to the most retarted timing position possible within that slop range. the Beta timing is set quite close to TDC, if you advance it too close to TDC by not paying attention to the above it may shear flywheel keys.