Exhaust Nuts

Not open for further replies.
Jul 1, 2009
Country flag
The bike is an 83 Commando Roadster. For some reason the right side exhaust nut keeps coming loose. It is not unscrewing as the securment tab is in place, but seems to be coming loose in the threads. When I take it apart the gasket is burned out. I put in a new gasket and tighten it done and its fine for a while. Damage is being done to the threads in the head, the left side stays tight. Any suggestions greatly appreciated
Safety wiring it would probably be best, but I find that if I torque to 60 lbs-ft or so, then retorque while hot and running after the next few outings, after that they stay torqued and don't loosen unless I want 'em to (apropos of the latter, I use antiseize on the threads). Good luck.
I found with mine that I needed to keep tightening the nuts for a while as the exhaust gaskets compressed. Then they stopped needing tightening. I safety wire them to the rocker cover nuts, so can easily check whether they are tight or not by feeling the tension. Plus the safety wire is very cheap (garden supplies) though not that good looking.

Best regards, Phil.
norsa1 said:
For some reason the right side exhaust nut keeps coming loose. It is not unscrewing as the securment tab is in place, but seems to be coming loose in the threads.

If as you say, the nut is not unscrewing, then it is very likely that the threads in the head are worn.
As the head heats up, the alloy of the cylinder head expands faster than the steel exhaust nut which allows the nut to pull out of the head thread, and so it becomes loose. If exhaust nuts do become loose then that can accellerate the rate of thread wear, so it does need fixing as it will only get worse.
You could try using the bronze exhaust nuts, as they expand at at similar rate to the head so tend to stay tighter than the original steel ones, but the only permanent cure (if it's done correctly?) is to get a threaded insert fitted to the head.
Dunno why, but the right side comes loose on both my 850 and my brother's 72 750. Left side comes loose much less often.

One recommendation that I have is to use a different crush washer. The prefered item is Suzuki p/n 1481-01D00. They are steel and don't deteriorate like the copper ones most people use.
You can buy brass nuts from Norvil which aree better, having a similar thermal expansion rate ot aluminium.
However If you get the bike good and hot and really give them a good nip they should not loosen.
Are you pulling the exhaust nut up again with the engine hot? If you do this with a 2ft extension on the usual tool and pull up as hard as you can it will stay where it is. If the threads strip then they were on the way out anyway and needed renewing anyway.

I've given up on all locking devices and just haul it up real hard while it good and hot - no more problems.
On mine I have noticed something that I would like to mention to you guys for comment. As far as the right side goes I too have had this happen on the right side, Here is what I found. I started having a problem with the kick start lever hitting on the pipe as I would tighten the right side it would slowly rotate the header pipe ever so slightly until it would hit. What I think happens is that as it does this it puts a bit of tension on the nut and this over time causes the pipe to return back to the position where there is no tension and that backs the nut off a bit. Try to have someone hold or you could tie the header pipe with a piece of wood in a position against the frame that it wants to be with no load and then tighten the nut. I don't know if this makes any sense or if this will help your issue but it did seem to help both problems for me.
Not open for further replies.