Necessity of replacing engine-mounting nuts

[basdj]

Hi,

I have recently stripped my GS500 to get the frame powder coated. Currently I'm rebuilding it, but I read in the GS500 manual that you cannot re-use the engine-mounting nuts. I called the dealership, and they said they never heard of something like that. What sould I do? Replace all mounting nuts, or use the same ones with loctite?

Bas (The Netherlands)


ps. I have got a GS500E from 1993.

[scratch]

I don't know. But I would suspect that you shouldn't have to. I go have a look at me bike...as it turns out, the few through bolts have self locking nuts on them, and look perfectly reusable. I guess it would depend on how they are after you take them off. If they deform, such that if you try to thread them back on, they wont go, replace them.

Hope that answers your question. But I suspect that one of the racers here will have a better, more definite answer, since they routinely take their engines in and out of the frames frequently enough.

[basdj]

thanks, self locking nuts usually have some white plastic right? or are their other kind of self locking nuts?

Thanks!

[scratch]

There are other kinds. These, for instance, have two metal tangs on the top of the nut, that put pressure on the threads. If the tangs are bent out of shape, they may lose their ability to exert the type of "spring" pressure that I suspect they do.

[yamahonkawazuki]

it usually is not recommended to re-use nuts/bolts that have been torqued. i do quite often, but it is said that they lose some of their tensile strength after being torqued. :dunno: up to you, look at them closely, if any doubt replace

[Bob Broussard]

Just re-use the bolts/nuts.
I have switched motors 100s of times with absolutely NO problems.
Don't sweat it.  

[JamesG]

same here.

I think its just a bit of CYA on Suzukis part.

[KevinC]

Not entirely. Those nuts lock by virtue of the deformed metal threads. That locking feature does not work well more than once. But the real reason they say not to use them is the torque spec.

The metal type lock nuts require a known torque to turn them on the first time. Suzuki wants a certain tensile load on the engine mounting studs to control vibration and have the engine become part of the frame structure. The torque numbers they have documented to achieve this are with new nuts, with a known torque requirement just to turn them onto the threads.

With used nuts, the torque required to put them on each time will go down with each re-use. If you use the torque number that Suzuki provides with used nuts, you will be putting a larger than intended tensile load on the engine mounting studs.

Is this a real problem? Well, you could actually permanently stretch the engine studs with the large tensile load, or start to yield the engine cases. The frame may not work as intended.

I re-used the nuts, but I took a bit off the torque spec, and used Loctite.

[basdj]

Thanks! I'm goning to re-use the nuts, with loctite. I will check the nuts now and then, to make sure their still tight. Hope they won't come off