Snapped bolts flywheel California 1100 EV

[NorwegianRider]

Hi,
First time Guzzi owner and first time on this forum.

Recently had a breakdown doing 80 km/h on a highway when I suddenly lost power/transmission (with some horrible noises included).
Managed to get the bike on a trailer, where I've dismantled it and found that the grade 10.9 bolts connecting the crankshaft and flywheel had snapped.
Unable to find any other faults: Engine turns fine by hand, gearbox turns fine by hand (all gears OK), drive and cardan OK.

Current plans are to just get new bolts from Stein Dinse, put the bike back together and hope for the best. But is the damage/marring on the mating surfaces a problems? I can always replace the flywheel, but worried about the crankshaft surface.
Are there any other things I should check for damage?
And any advice on other things that would be smart to check/replace while I have the bike apart?

Any advice is greatly appreciated, thanks.

[Dave Swanson]

The flywheel does not look like it should be used again.  Perhaps if you have a machine shop than can skin cut the surface it might be saved, but the divots in the face look deep.  A perfect mating surface is critical here.





The crankshaft looks like it should clean up sufficiently using finishing stones after the bolts are extracted. 

I can come up with no reason for the bolt failure other than improper torque being applied the last time apart, and/or lack of proper locking tabs or correct Schnorr washers. 

Welcome to the forum and keep us informed on your progress. 

[NorwegianRider]

Thanks for the quick response Dave.
I'll order a new flywheel, and do my best at dressing up the crankshaft.

The bolts were installed with these washers;




Is it usual practice to use locking tabs?

[Dave Swanson]

Thanks for the quick response Dave.
I'll order a new flywheel, and do my best at dressing up the crankshaft.

The bolts were installed with these washers;




Is it usual practice to use locking tabs?

Locking tabs are the old way of doing it.  Those Schnorr washers are correct for the application.  Do you know if the correct torque was applied last?

[Wayne Orwig]

Thanks for the quick response Dave.
I'll order a new flywheel, and do my best at dressing up the crankshaft.

The bolts were installed with these washers;




Is it usual practice to use locking tabs?

Those are correct. Maybe someone reused the bolts and washers. That is not the place to go cheap. Always use new fasteners there and of course torque them properly.

[Denis]

Another possibility is that the flywheel bolts were reused, which is a big no-no.

[JoeW]

There are several reasons for that failure, improper torque, either too loose or too tight. Wrong bolts used. The ring gear bolts are 8.8 harness and torque is 25 ft lbs, I have seen these bolts mixed up.  They are supposed to be 10.9 hardness bolts torqued to 35 ft lbs. I use serrated wave washers and blue Lock-tite

[EldoEVert]

I'll probably get ridiculed but here's my method of securing the flywheel. First of all I aquire new bolts and wave washers. I then clean the mating surfaces with brake cleaner to assure there's no oil present. Then I bolt the flywheel on with two of the used bolts and torque them to about 15 lbs. Next I use blue locktite and insert new bolts with wave washers in the remaining holes and torque to about 15. Then I remove the first two and put the remaining new ones in there and finsh torquing to 35lbs. This way there's no chance of getting locktite between the mating surfaces. Call it anal but that's me. It's alot of work to get to the flywheel and I don't want to have to go in there twice.

[Antietam Classic Cycle]

This is the type of washer used by the factory after lockplates were no longer used, and are what I use with 10.9 bolts. https://www.mcmaster.com/93501A030/