ETZ251 Primary sprocket (the big one by the clutch) shearing

[thomaskwscott]

Hi Guys,

About a year ago the primary sprocket from the back of the clutch that is splined onto the gearbox shaft on my 251 sheared and left me stranded. I tore the engine down and rebuilt it with another sprocket and everything has been fine until recently when i've noticed a jumping when in low gears and high revs. This feels like the chain is slipping so I checked tension and found it spot on. However, it kept happening so last night I took the left side cover off and sure enough there is play in the primary drive sprocket. The retaining nut is done up to correct torque and the lock washer had not moved so I can only assume it is shearing on the splines again. Has anyone heard of this before? Is it a common thing with ETZs? and should there be play in that sprocket on the splines?

Any thoughts much appreciated.

Thanks

Tom

[thomaskwscott]

Ignore me, there was no play in that sprocket. I hadn't removed the clutch yet and what I was sewing was play in the splines in the clutch plates (which I was expecting). I guess the only other thing to check is a worn rear sprocket. I'd have started there but because of the enclosed chain it's easier to remove and refit clutches than rear sprockets on an Mz...

[DAVID THOMPSON]

i had the nut on the chain sprocket on the transmission come loose
i was doing a normal inspection and looked at it after putting on a smaller sprocket on it
about 3 weeks before
locking compound is needed on that sprocket nut
do have a look at the transmission sprocket nut often
mine is the rotax powered 4t and it gets expensive when you ruin the trans out put shaft

dave

THAT enclosed chain needs taken apart and inspected .. and greased every winter
so no down time in summer