exhaust bolts fall out

pedal no mo · Aug 2, 2013

my exhaust bolts keep falling out..tried "red lock tight"...FAIL...THEN stripped one side,,tried JB weld on threads...FAIL...it has m6-100..bolts?what would i tap the next size to??????any tips to stop these !$!%!# bolts falling out??

crassius · Aug 2, 2013

Re: !@#$^% exhaust bolts

sounds like your muffler hanger at the bottom of the muffler may not be tight

those studs won't support all that weight by themselves

MotorBicycleRacing · Aug 2, 2013

Re: !@#$^% exhaust bolts

pedal no mo said:
my exhaust bolts keep falling out..tried "red lock tight"...FAIL...THEN stripped one side,,tried JB weld on threads...FAIL...it has m6-100..bolts?what would i tap the next size to??????any tips to stop these !$!%!# bolts falling out??

You might need to support the weight and leverage of your
muffler so there is less stress on the exhaust bolts.

If the 6 mm threads aren't too far gone re-threading with a 1/4 20
tap can work.

Never use JB weld or red locktite on exhaust bolts.

Do you have a pic?

Good luck and let us know how you end up fixing it.

Venice Motor Bikes · Aug 2, 2013

Re: !@#$^% exhaust bolts

Do the studs come out of the cylinder?, or the nuts come loose??

One of the things I do is to re-torque the nuts right after the first run, (while the engine's still hot).

MotorBicycleRacing · Aug 2, 2013

Re: !@#$^% exhaust bolts

If that is the bike you are having the problem with is there
any support for the pipe except for the head studs?
That's a lot of leverage! and vibration will do a number on
those studs.

The pic shows studs and not bolts, there is a difference....

Venice Motor Bikes · Aug 2, 2013

Re: !@#$^% exhaust bolts

MotorBicycleRacing said:
If that is the bike you are having the problem with is there
any support for the pipe except for the head studs?
That's a lot of leverage! and vibration will do a number on
those studs.

The pic shows studs and not bolts, there is a difference....

That's some good detective work there Neil!! (^)

pedal no mo · Aug 2, 2013

Re: !@#$^% exhaust bolts

Venice Motor Bikes said:
That's some good detective work there Neil!!

HI YA guyz..yea their is a support nut welded on the back side of the muffler and thru bolted to the frame...and yes i started with studs and they fell out,,,then tried bolts ..are the stud threads different ? should i try to put back studs or?? thanx guyz

crassius · Aug 3, 2013

Re: !@#$^% exhaust bolts

I've had good luck putting heli-coils in those

for the clutch side, you can break a little piece off the fin that blocks the end of the hole so your tool will go well into the hole and for the magneto side, you need to drill the hole right into the front head stud chamber to make room for your tool (obviously, you need that stud out to do it)

biknut · Aug 4, 2013

Re: !@#$^% exhaust bolts

I also recommend heli coil to repair the threads. That actually makes it stronger than stock, and only takes a few minutes.

crassius · Aug 4, 2013

just remembered - if you heli-coil them, you'll need to use bolts rather than studs to mount the exhaust

KenX · Aug 26, 2013

The lines of the exhaust with the frame look great. Similar to mine. I did put a couple of stainless steel clamps on lined with self adhering silicone tape between the frame and the exhaust. I was concerned about the problem you are having. No guarantees but seems to be working nicely.

KenX · Aug 26, 2013

Re: !@#$^% exhaust bolts

Venice Motor Bikes said:
That's some good detective work there Neil!!

Yes indeed it does seem like a good observation.

Toadmund · Sep 5, 2013

Was going make my own thread about this issue, I too tried JB weld, but it stopped holding after a while.
Then, what I was going to make a thread about, is muffler cement.

Would muffler cement work for a stripped exhaust stud hole?

I got a 1/4 20 bolt just in case it wont work.

maniac57 · Sep 5, 2013

Toadmund said:
Was going make my own thread about this issue, I too tried JB weld, but it stopped holding after a while.
Then, what I was going to make a thread about, is muffler cement.

Would muffler cement work for a stripped exhaust stud hole?

I got a 1/4 20 bolt just in case it wont work.

No. Nothing will fix this for long except retapping the hole or a helicoil.
The helicoil is a excellent way to repair stripped aluminum threads.

deskman · Sep 6, 2013

another vote here for helicoil. one of my threads got very badly stripped, almost bought a new cylinder head...then once i learned about heli coils it was a miracle! bolt stays a thousand times tighter than before. i was joyed when the second bolt stripped because then i got to put another helicoil in, now my exhaust is trouble free!

Toadmund · Sep 6, 2013

I gots me a job now, so I'll look into a heli-coil once again.
They are not cheap.
But they would be a lot stronger than the original threads, lots of surface area on the outside, and strip proof on the inside with normal use because they are stainless steel.

deskman · Sep 11, 2013

yeah i was pretty annoyed when i saw the price. but it usually comes with a large pack of coils so you could keep using them for a while.

SuedePflow · Sep 11, 2013

Helicoils are great, but Time-Serts would be an even better option. Time-serts are stronger, positive locking (don't come loose like Helicoils can), and there do not have a "bottom" like Helicoils do.

crassius said:
just remembered - if you heli-coil them, you'll need to use bolts rather than studs to mount the exhaust

Why is that?

crassius · Sep 11, 2013

a stud would no longer have a 'bottom' to tighten into - a lock washer could hold a bolt or the nut on a stud, but the stud itself could loosen thru the nut

SuedePflow · Sep 11, 2013

crassius said:
a stud would no longer have a 'bottom' to tighten into - a lock washer could hold a bolt or the nut on a stud, but the stud itself could loosen thru the nut

I'd have to disagree. A stud doesn't need to bottom out to work. Tightening is done with the nut. Once the nut is torqued to spec, a combination of friction between the threads of the stud and cylinder head and preload of the stud itself will keep the stud tight in its place. The only way for the stud to come loose is for the nut to first come loose.

I have a pretty extensive knowledge of the function of all fasteners in general from years of racing. My previous aluminum cylinder head on my race car had every hole heli-coiled and I replaced every bolt with a stud and nut. It worked flawlessly. I never once had a stud/nut come loose for the valve cover or either manifold. My new cylinder head is identical except that I used Time-serts instead of Heli-coils.

But if you did want a stud that offers a positive stop of some sort, I would rather it bottom out at the top of the threads than the bottom. That would require a stud like this:

crassius · Sep 11, 2013

opinions often vary - any place with a lot of vibration is where I try to err on the safer side

besides, I see no reason to deal with a stud on a non-blind hole

exhaust bolts fall out

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