Shearing woodruffs

[sydduckett]

I sheared the woodruff key about 200 metres out from home. Went home replaced the key and swapped for another flywheel. Mucked about with a few ofher things and went back out ran likea dog straight away. Woodruff sheared again. Changed for the 3rd time but havent kicked overbyet. Im pretty sure the 2nd one sheared on kickover but cant be sure. Decided to check chaincase. Kickstart was rubbing badly on the casing and the edge of the clutch. Plunger for the ramp was loose....
Then i looked at the chain which was loose. Seemed the. Nylon gurds must have slipped a bit although they.were to tight to move by hand. Iv readjusted the guards to take up the slack on the chain and ground the kickstart shaft and threadlocked the plunger.
Questions i have, is the slack chain the likley reason for the shearing of the woodruff or am i barking up the wrong tree? It was tightened right up on both occasions
Next one even with fulla adjustment on the ramp i cant the splines to allow the kickstart to rest less than 2inches from the bump stop.

Ta
Sef

[holty]

hi,
the woodruff key is only to locate the flywheel while you torque up the nut, the taper on the crank and flywheel then holds them together, usual cause is a loose nut or a bad taper, i woul recomend using some fine lapping paste/grinding paste and lap the flywheel onto the crank until you get a dull grey colour on the crank and flywheel taper, you may have to lightly file high spots first, then refit flywheel and new key, i think i would put a little studlock on there as well as on the nut.

[sydduckett]

I lapped with coarse and then fine and got a good colour. Im wondering if some reason its not pulling onto the taper even though its as tight as i can get it.

[PeteB]

I lapped with coarse and then fine and got a good colour. Im wondering if some reason its not pulling onto the taper even though its as tight as i can get it.

Just a thought: Is there some muck in the woodruff keyway, or are the keys being used too high in profile? I've heard somewhere that some keys are, meaning the flywheel torques onto the top of the key rather than the crank taper when the nut is tightened. Hope this makes sense!

[Adam_Winstone]

"are the keys being used too high in profile? I've heard somewhere that some keys are, meaning the flywheel torques onto the top of the key rather than the crank taper when the nut is tightened. Hope this makes sense!"

... check this out as I experienced it recently.

[eden]

I lapped with coarse and then fine and got a good colour. Im wondering if some reason its not pulling onto the taper even though its as tight as i can get it.

Just a thought: Is there some muck in the woodruff keyway, or are the keys being used too high in profile? I've heard somewhere that some keys are, meaning the flywheel torques onto the top of the key rather than the crank taper when the nut is tightened. Hope this makes sense!

could be some paste left at the bottom of the keyway making the key too high.

[stokky]

Interesting.............

must be a few years back now, one of mine sheared woodruff key, think was 3 times in as many weeks.

At same time, I also knew the chain was far too slack.
When eased off throttle going down hill, you could feel it sort of chugging as chain tightened and slackened.

I tightened the chain (well swapped it out actually.
At same time I took same advice as you've got on here, and lapped flywheel to crank.

3 years later - no problems and all still running fine.

Still not certain which or both, fixed problem.

[sydduckett]

Im hoping it was the slack chain. The woodruff was quite low, i even wondered if it was to low. Im going to lap it again and refit the flywheel and keep my fingers crossed.
Thanks lads
Sef

[YAMLAM]

Loctite bearing fit (601) belt and braces.

[rosscla]

Loctite bearing fit (601) belt and braces.

Where?