I've got a fiend with an 02 RK and he keeps breaking motor mount bolts. Anybody have any insight?

 

What kind of bolts is he using? I'd almost bet he's using a grade 8. Grade 8's are provide the strongest clamping force available. But they are intolerant of vibration and lateral stress. Grade 5's will bend a little and take a set, but won't break.

1. Ideally, bolts should only provide clamping force, and nothing else. Locating and alignment of parts should be done with a dowel pin. Check and see if his mounts should have a dowel pin, but don't.

2. Check and make sure all the parts line up correctly. If you have to torque something over line up the holes, that creates lateral stress.

3. Clean all the bolt holes with thread chaser.

4. Make sure the clamping surface is flat, and perpendicular to the bolt. If it's not flat, it will place an angular load on the head. Use a 6" piece of threaded rod and a carpenters square.

5. Torque to specs with a torque wrench. Check the manual to see if the specs are dry or wet.

6. Use a grade 5 bolt.

 

I've heard of this problem before. There is a proceedure for aligning the motor in the frame, but I can't remember all the details. Call your HD tech and ask them how to do it.

 

Is he one of those really big, strong, monstrous fiends? Maybe he's just tightening it too much and its already on the verge of cracking before the bike even moves.
What are you doing keeping a fiend around, anyway?

 

yep I have broke them my self ,I went to a grade 8 with nylon locking nut . Trashed the motor mout also now with the new inpoved hard mounts the vibration is bad I loosened the center bolt hoping it will brake the mount like it was befor loved the ride befor the new mounts.

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