Crank won’t turn when flywheel nut is tightened.

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cartmel808
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Main scooter: 1975 Vespa Rally 200 Femsa
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Thu Sep 20, 2018 10:38 pm

I managed to wreck the flywheel on my vespa a couple of weeks back through over tightening the nut, which stretched the boss & lead to the flywheel nut working loose at speed & shearing the woodruff key. I didn’t have a spare with me & so ended up doing a 4 mile walk of shame home...

Anyway - a new replacement flywheel arrived today so I’ve tried fitting it tonight, but once I start to tighten the flywheel nut the crank doesn’t want to turn & if I try to torque the nut down it basically locks solid.

There’s no signs of the new flywheel binding against the stator/casing - so would this point to an issue with the fly side bearing - or worse - the crank?



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Last edited by cartmel808 on Thu Sep 20, 2018 10:38 pm, edited 1 time in total.

Norrie Bodge
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Fri Sep 21, 2018 8:33 am

Possibly if the crank is twisted ?
can you not try the new flywheel on a mates bike to see if it fits & runs ok

Fruitjuice
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Fri Sep 21, 2018 11:31 am

See if it's binding on the stator bolt heads, they're usually awfully close....
Life shouldn't be a journey to the grave with the intention of arriving safely in a pretty, well preserved body, but rather to skid in broadside, in a cloud of smoke, thoroughly used up, totally worn out, loudly proclaiming: "WOW, WHAT A RIDE"

gaz_powell
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Fri Sep 21, 2018 7:20 pm

What origin is the crank and the one it replaced? Like for like?

gaz_powell
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Fri Sep 21, 2018 7:25 pm

Ment so say flywheel not crank!

cartmel808
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Fri Sep 21, 2018 9:37 pm

It’s a Pinasco Flytech flywheel - and after having had another look at it tonight, the problem is definitely with the new flywheel.

I’ve tried a standard Piaggio stator & flywheel on tonight & that was fine, no binding & engine turns free - so no issue with the crank - thank god.

When I’ve had a better look at the new Pinasco flywheel the outside diameter of the boss is bigger than that on the old one for some reason - so when tightened, the end of the boss/taper was fouling against the stator & wouldn’t turn.

Yet another expensive part that’s not fit for purpose!


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railfancwb
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Tue Sep 25, 2018 5:32 pm

If you know someone with a large enough metal lathe they might - I say MIGHT - be able to shave enough off the binding areas that the flywheel would then fit properly.


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