Topic: exhaust bolt torque specs?

[slowjo]

what is the torque specs for the exhaust bolts that thread into the head ft/lb? And should I use some kind of thread locker or antisize on the bolts? The bike is a 1971 CB750.

[fire_strom]

No one knows?

[Alan F.]

There isn't actually a torque spec on those bolts, just tighten finger tight plus one half turn, then fire it up and check for leaks, if you find a leak go 1/4 turn tighter.  The exhaust gaskets are copper crush gaskets and sealing them doesn't require much.  Over tightening can strip threads or worse break a bolt or stud off in the head.  Thread lock isn't a requirement here, I don't recommend it.

[fire_strom]

Well then I over torqued the crap out of it. Finger tight and 1/4 turn would have been sloppy lose. I went the other direction. Firm push on the short wrench tight. Doesn't leak and it didn't strip. I sure do like just dialing in a number and not sweating to feel the rightness though. Some one must have a number. I'm guessing 20-25 ft/lbs.

[Alan F.]

I'd guess more like 6 ft/lbs.

[MCRider]

I'd guess more like 6 ft/lbs.

I agree with both of your posts. In applications with crush washers, sparkplugs, oilplugs, exhaust bolts, tighten to crush the washer, test for leaks, tighten as necessary.

As to chemicals, whenever you're running steel into aluminum, it can't hurt to use anti-seize. With as many posts as there have been about people snapping off exhaust studs etc. anti-seize seems to be warranted.

[MCRider]

Well then I over torqued the crap out of it. Finger tight and 1/4 turn would have been sloppy lose. I went the other direction. Firm push on the short wrench tight. Doesn't leak and it didn't strip. I sure do like just dialing in a number and not sweating to feel the rightness though. Some one must have a number. I'm guessing 20-25 ft/lbs.

There is no need for that much torque, you're just asking for problems later on. "finger-tight" may be a little loose, but the idea is right. Simply not too tight. Tight enough that they don't leak, that's all. 20-25 ft-lbs is more than the cylinder head gets. The pipes aren't going anywhere.

[MauiK3]

I also was concerned with this issue so here is what I did.
I have a small Milwaukee 12v screwdriver that has a very nice stepped clutch that has a nice light touch. I evenly tightened the screws watching that the exhaust flanges stayed even. I kept creeping up the torque setting watching the flanges settle. I went down until I could still get an 0.035" feeler gauge between the flanges and the head on both ears. That way I know I still have a little bit to go. They really do tighten easy and the torque is low. I just went by space under the ears.

[BomberMann650]

I think the manual specifies it at 8lb with the other 10mm hex nuts.

[Deltarider]

Forget about the torque specs for these small bolts. No mechanic would use a torque wrench for them. Nothing beats your own senses. Torque it as light as possible, just enough to let the copper gaskets seal.