[Magoo]

This one has me miffed.
Twice in three weeks the long bolt at the base of the engine mount has simply sheared off, thread, nut and all.
Vibration issue?
Is it getting too hot?
I keeping having to kick the bolt back in and if that thing falls out and hits the spokes I'm screwed!

[ace.cafe]

Make sure all the other engine mount bolts are tight all around.

[ROVERMAN]

Possibly try the old method and leave all the engine mounting bolts just loose enough to allow some movement. Start and run the engine for a few minutes then torque all the bolts to spec. This will theoretically relieve any stresses present.
Roverman.

[gashousegorilla]

  I would also have a look at the bolt ...I believe it is the one right next to the one that is breaking, and to the right in your pic... And make sure it is running STRAIGHT across the bottom of the Engine. It will be the one that threads into the kick stand mounting plate, witch also acts as an engine mount on the left side of the bike.

[Norm]

Is blue thread-locker a possible easy solution to this?

[Magoo]

Haha, sometimes blue loctite just isn't the miracle cure. If it was just the nut coming loose and falling off then problem solved.
The whole end has snapped off. Nut, thread and all so there's obviously undue stress on it.
Two bolts in three weeks.

[Arizoni]

That bolt also sheared off on my G5.
It is the lower rear engine mount and if you tighten it down to the torque recommended in the Service Manual and you used a normal bolt to replace it, it will shear off again.  The nut/bolt should be torqued to 50 N/M (37 lb/ft).

The size is a M10 X 260mm length and I couldn't find one in a high stress material.

I didn't want to wait for a week or so for a replacement bolt from CMW plus they probably wouldn't sell me one anyway because I'm not a dealer, I used another method to solve my problem.

At my local Ace hardware store, they sell threaded stock and nuts.  They have a low cost low strength threaded stock but it will not take the loads that are needed.
They also had a rather high cost heat treated threaded 3/8-24 UNF threaded stock which I bought.  I also bought two grade 5 nuts in that thread size and two steel flat washers.  I had to buy a new HSS hacksaw blade to cut the threaded stock down to the needed length.  (My old used hacksaw blade would barely scratch it.  It's that tough,)

Anyway, with that torque applied, my fix has lasted over 2 years.  Oh.  At the high loading produced by that torque, you won't need any blue thread locking stuff.  The 7900 pound load from 37 lb/ft of torque will keep it from unscrewing.

[Arizoni]

That bolt also sheared off on my G5.
It is the lower rear engine mount and if you tighten it down to the torque recommended in the Service Manual and you used a normal bolt to replace it, it will shear off again.  The nut/bolt should be torqued to 50 N/M (37 lb/ft).

The size is a M10 X 260mm length and I couldn't find one in a high stress material.

I didn't want to wait for a week or so for a replacement bolt from CMW plus they probably wouldn't sell me one anyway because I'm not a dealer, I used another method to solve my problem.

At my local Ace hardware store, they sell threaded stock and nuts.  They have a low cost low strength threaded stock but it will not take the loads that are needed.
They also had a rather high cost heat treated threaded 3/8-24 UNF stock which I bought.  I also bought two grade 5 nuts in that thread size and two steel flat washers.  I had to buy a new HSS hacksaw blade to cut the threaded stock down to the needed length.  (My old used hacksaw blade would barely scratch it.  It's that tough,)

Anyway, with that torque applied, my fix has lasted over 2 years.  Oh.  At the high loading produced by that torque, you won't need any blue thread locking stuff.  The 7900 pound load from 37 lb/ft of torque will keep it from unscrewing.

[ChrisS]

That bolt also sheared off on my B5.  Several times. Tried bolts from McMaster-Carr and treaded stock, all sheared.  Finally tried some solid round 3/8 stock, cut to size, cut threads on both ends and applied. Been a year and it's still holding.  But I still look at that bolt every time I get off the bike.

[Ducati Scotty]

Might check that one to make sure it's tight when I get home.  Just 'cause.

[gashousegorilla]

  What cured mine was to fix the misaligned mounting hole on the left side motor mount/ sidestand plate.  Both of those long bolts are either through or threaded into that plate.  The way the plate was situated  with the misaligned hole at the rear of the plate, made it cocked. Causing the bolt running under the engine to be at an odd angle to the plate, as the plate had been shifted down, so the rear hole in the plate could be forced to align. When I undid that rear screw in the plate, the threads on it were destroyed from being forced in.  My nut had been coming loose all the time.... After I opened up that hole and realigned it all, it hasn't happened since.   

[FiRE Comms]

found this bolt sheared yesterday as well.  a section of 3/8" B7 threaded rod did the trick.

[NorEaster]

wow... I hope one of the design engineers reads this forum

[Ducati Scotty]

Anyone who finds a failed engine mounting bolt, do yourself a favor.  Warm up the engine with a ride and then shut it down.  Loosen ALL of the engine mounting bolts, just enough so the can slip.  Start the engine, and with it running, tighten down all the bolts.  This helps relieve any pent up stress in the frame and should make for fewer vibes overall.

Scott

[FiRE Comms]

hmmm, I did have to jack up the motor to line up the chase, thanks for the tip!