Engine mounting bolt length for case savers?

[seano]

I'd like to mount a set of case savers on my 1980 GS850G. One of the mounting points is at the "pivot shaft" - it's the big long (10"?) engine mounting bolt that goes through the front of the crankcase just above where the upper and lower halves of the crankcase meet. I'm thinking this shaft is not long enough to accomodate the case savers as the PO installed a bolt that's way too long and really doesn't look strong enough. I'd like to try with the correct bolt, but don't want to waste the money if it won't work. If anyone could give me a measurement on that bolt, it would be really helpful.
Thanks

 

[dr_fosg8]

I had the PO do the same on my 82 1100 gl. I presume it is due to the bolt being to short to accomodate the additional thickness of the case guard mounts.

 

[bwringer]

If you look on the crankcase fiche, you'll see that the original bolt is 12mm diameter X 235mm length. (1.25mm thread pitch).

However, you'll need a slightly longer bolt or a length of threaded rod in order to mount case guards.

Here's where it gets a little weird...

Case saver kits were originally supplied with a piece of threaded rod with washers and two nuts, but it wasn't metric -- they used a 1/2" rod with fine threads (20 tpi). This is nearly indistinguishable from 12mmX1.25 threads, by the way... 1/2 inch = 12.7mm, and 1.25mm = .0492" (20 tpi = .05")

Guess how I figured this all out. Go on, guess... http://bwringer.com/gs/images/gaah.gif
The hard way, that's how... lots of trips to Ace Hardware.

Anyhoo...

I just went into the garage, and an exact length measurement is difficult, but I think you'd be safe with a 12X250mm bolt. I couldn't find anything that long at McMaster-Carr, but you can get 12mm all-thread in meter lengths (although 1.25mm thread pitch is a lot more expensive -- most of it is 1.75mm, which should still work fine as long as it's at least grade 8.)

You can also get 1/2" fine thread (20tpi) bolts and threaded rod in the proper grades (I would not use low-grade fasteners for this -- that bolt is kinda important...). You'd need a 10" bolt, I think, but please verify this on your bike before spending actual money.

 

[beardedmonkey]

Hey man, where'd you find your case saver? I've been looking for one for my '78 750.

 

[seano]

Thanks bwringer for all the info - very helpful! The fiches I was looking at didn't have any measurements imbedded in the part #. Gotta remember Alpha sports!!
The bike came w/ the case savers. Lucky me

 

[FLHGSRay]

This is another area where this site saved my a$$. I was removing the case savers from my 1000 and stumbled on a thread about someone punching a hole in their engine case with a too long bolt in a lower engine mount. Got to checking mine and sure enough, if I had reused the bolts that were on the case savers, I'd have punched a hole right through the engine block. Instead, I went and bought new bolts that were too long and cut and rethreaded them to the right length.