Exhaust manifold bolts coming loose

[black charger]

The exhaust manifold bolts at the pipe keep coming loose on my 95xp with a 720.I have put in all new bolts,new lockwahers,new bushings,used blue locktite and torqued to spec.The bolts stay tight during a casual cruise,but,when running hard and jumping around they come loose and back right out.Could I be looking at new motor mounts?Or is there a trick to keeping these things tight.Also could Nordlock washers solve the problem?Any suggestions would be appriciated.

 

[68ragtop]

Your talking about the three bolts, & one nut that hold the pipe to the manifold, correct? Do you have the two additional bolts, spacers & bushings installed that secure the pipe to the manifold as well?

 

[black charger]

Yes,3 bolts and one nut.New bushings bolting the pipe on.They still come loose.Also a new gasket between pipe and manifold.

 

[68ragtop]

That seems odd. The taps aren't getting corroded are they? Do the bolts fit loose in the taps?
I have had several upright 580's & a 720 & haven't had that happen yet. Hhmmmmm.

 

[black charger]

Bolts seem to fit fine.By the taps being corroded i assume you mean the threads in the manifold itself.

 

[Crofoot50]

I had this problem on both my skis 657 motor and 720. Vibration is causing them to loosen up. Bad motor mounts or improper alignment is prob what is the cause of your issue

 

[Dr Honda]

You are probably over torquing them. They only get tightened to about 18 Lb/ft. If you over tighten them... they stretch, and the gasket crushes. Then... when the engine cools... they become loose. AND... the next ride... they vibrate out.


So... get a new gasket, bolts, and lock-washers, and put them together at the proper torque.

 

[black charger]

You are probably over torquing them. The only get tightened to about 18 Lb/ft. If you over tighten them... the stretch, and the gasket crushes. Then... when the engine cools... they become loose. AND... the next ride... they vibrate out.


So... get a new gasket, bolts, and lock-washers, and put them together at the proper torque.

That makes a lot of sense to me,this coming weekend I'll put in anew gasket.One furthur question.How can you judge the torque on the one nut, as the three others you can get a torque wrench on the nut you can't.

 

[Robj]

I had this problem on both my skis 657 motor and 720. Vibration is causing them to loosen up. Bad motor mounts or improper alignment is prob what is the cause of your issue

If it was my ski, I would check the alignment too. Especially if you have an alignment tool handy. I can see how an improperly aligned motor would induce excessive vibrations.

 

[Dr Honda]

That makes a lot of sense to me,this coming weekend I'll put in anew gasket.One furthur question.How can you judge the torque on the one nut, as the three others you can get a torque wrench on the nut you can't.

once you torque the others... you will have a good feel. Or... use a crow's foot.

 

[Sportster-2001-951C-Stock]

I agree these should not be overtorqued, and the spec assembly instructions should be folowed exactly for best results.

That said, I have experienced similar phenomenon in other cases not related to Seadoo manifolds where I was able to resolve the problem by installing a stud system instead of a bolt system. I found when cut to proper length, studs make better use of the existing threads and can be bottomed into the blind hole. Sometimes this may not be possible due to the geometry involved accessing the fasteners, but I've experienced much improved results in most cases.