Front engine "swing arm" bolt

[BCS Guy]

So I am trying to install a set of 3 point case guards on my wife's 81 GS850. They line up and everything is all good, but the swing arm bolt is to short for the washers, mounting tab, and nut. The length of the bolt is 235mm which match with what I am seeing here (pn 35):
https://www.suzukipartshouse.com/oemparts/a/suz/50d40177f8700230d8b4e4c6/crankcase

I was wondering what other people who put these on did. Did you source a longer M12 bolt, or did you remove the washers, or did you spend the money and buy a bolt stretcher?

Thanks,

Dan

 

[bwringer]

Back in Ye Olden Dayes, the case guards came with a long piece of all-thread and the appropriate washers and nuts to replace this bolt.

You can order up an M12 X 300mm length of all-thread from McMaster-Carr, then cut off what you don't need. I'd get the zinc-plated class 8.8 rod.

There are also places you can find an M12X250 bolt:
https://www.belmetric.com/12x175-coarse-c-506_510_399/bh12x250blk-hex-bolt-black-109-p-3543.html

Note that the thread pitch is 1.75mm, not the 1.25mm commonly used on other M12 threads on your GS. It'll work fine; just make sure you get the correct nuts. I'd use nylock nuts; this area is subject to some serious vibration.


Many of the case guards back in the day actually came with a length of fine thread 1/2" rod. It's really fun to discover this weird fact late on a Sunday when a nut gets lost, you don't have a replacement in your comprehensive stash of metric hardware, and the hardware stores are all closed. DAMHIK...



Also, one thing I'll mention: more than one GSR member has poked holes in their engine by using the incorrect length bolts on the lower engine mounts. They are different lengths on the left and right, so the kits supplied one replacement bolt, with instructions to move the longer one to the other side. There's very little clearance, so being just 5mm off will poke a hole in your engine and you will be sad and leaking.

Be EXTREMELY careful and paranoid with this. It's awkward as hell, but you have to get under there with a mirror and a good light and LOOK as you crank everything down. If your bolt extends much past the triangular nut plate and contacts the engine, STOP and create or find a shorter bolt.

 

[Guest]

A gs 850 is gonna have a bigger bolt than m12, have you actually measured it. ? Would have thought at least 15 or 17 mm

 

[Gumpster]

Some case guards are threaded on the right side so the long bolt screws into the case guard replacing the nut and allowing the use of the stock bolt.

 

[bwringer]

A gs 850 is gonna have a bigger bolt than m12, have you actually measured it. ? Would have thought at least 15 or 17 mm

Bolts are designated by the diameter of the threads, not the wrench size. Length is measured along the shank, not including the head of the fastener. The bolt is clearly called out on the fiche as 12X235.

On JIS fasteners, 12mm thread fasteners use a 17mm wrench or socket. Metric fasteners that use the the more common SAE (US) or DIN (Euro) standards would use a 19mm wrench.


The 1/2"-20 all-thread I found installed on my bike works out to 12.7mm diameter; there's juuuuust enough slop in the holes that it fits.

 

[bwringer]

Some case guards are threaded on the right side so the long bolt screws into the case guard replacing the nut and allowing the use of the stock bolt.

That's a pretty cool idea. Haven't seen one of those!

 

[BCS Guy]

Thanks for all that information. Mine most defiantly did not come with any hardware. Very good to know about the lower bolts. The lower bolt on the left hand side was missing before I started this. I replaced it, but I will double check that I am not making contact.