Exhaust header bolt question (GS450)

[Trevor76]

The bolts that were on the bike when I got it are fubared, they were mismatched -different lengths and different size hex heads.

So, can anyone tell me what size/length/pitch the correct bolts would be for a 1980 GS450 E? (or point me toward a table or chart that would have the information)

Just to clarify, these are the four bolts that secure the header pipes to the motor, at the flange.

Thanks!

[gearhead13]

I replaced my stock bolts with stainless allen heads for a while. The hex on a few of them got messed up too easily and I found that the nice stainless look disappeared with road grime and engine heat, so I recently replaced them with studs. 45mm x 8mm I think on mine, could go 50 or 55mm. Measure the threaded hole and then measure to the exhaust pipe flange to get length. Sometimes the fiche shows the bolt length in the part number as well.

[keman]

Double check the thread and size in the holes, Someone may have drilled out broken bolts and re-tapped up one size. I had to do that with three of mine.

[Trevor76]

Well I picked up four allen head bolts, 8mm x 40mm, 1.25 pitch. Seems that the pitch is wrong -the bolt will go in for a few turns then stop.
Doesn't look like the original threads of the holes have been tampered with but who knows...

Keman, exactly how do I go about checking the thread pitch of the holes?

[keman]

Trail and error, or take the old bolts to the hardware store and match them up with new stuff. I used 5/16 nf grade 8 on the three I had to re tap. They were the closest next size up, and I only have SAE taps.

Some folks try helicoil, or other thread repair, but personally, I would rather go a size up and re tap if it's not going to compromise the strength of the piece.

Don't think I would use stainless for header bolts. SS and aluminum are not friends when mixed with high heat and strength requirements. SS is OK for case bolts, and non critical areas.