Sudden louder exhaust; advice?

[BCKRIDER]

Last Monday took a 350 mile joy ride through our backroads. About 2/3 the distance noticed the bike sounded louder. (Noticeable with good ear plugs and and Shoei RF-1000.) Pulled over then revved up the bike (1992 K100RS) and the noise seemed to come from under the engine. There were also a few mild backfires, something new for this bike.

Since I am hardly any kind of mechanic, much less a road-side one, and the bike ran fine, continued on home. The next day I removed the belly pan and the bracket which it is attached to (thank you, Clymer) and discovered that there are two nuts connecting each exhaust pipe to the bike. Of the eight, one was missing. Found a nut with appropriate diameter and thread (thanks, Dad) and snugged it up. I also tightened up all the other bolts while I was at it with a socket wrench and extension to "firm."

I can tell you I was shocked that I was not only able to find the problem but also solve it! The running bike is now it's usual quiet self.

Gearheads: Is this something everybody should be checking every couple years? Is there a torque reccommendation or is firm good?

BTW, while I'm glad I don't charge myself $100/hour, (from start to finish would have been about $300) this was satisfying.

[roy]

Last Monday took a 350 mile joy ride through our backroads. About 2/3 the distance noticed the bike sounded louder. (Noticeable with good ear plugs and and Shoei RF-1000.) Pulled over then revved up the bike (1992 K100RS) and the noise seemed to come from under the engine. There were also a few mild backfires, something new for this bike.

Since I am hardly any kind of mechanic, much less a road-side one, and the bike ran fine, continued on home. The next day I removed the belly pan and the bracket which it is attached to (thank you, Clymer) and discovered that there are two nuts connecting each exhaust pipe to the bike. Of the eight, one was missing. Found a nut with appropriate diameter and thread (thanks, Dad) and snugged it up. I also tightened up all the other bolts while I was at it with a socket wrench and extension to "firm."

I can tell you I was shocked that I was not only able to find the problem but also solve it! The running bike is now it's usual quiet self.

Gearheads: Is this something everybody should be checking every couple years? Is there a torque reccommendation or is firm good?

BTW, while I'm glad I don't charge myself $100/hour, (from start to finish would have been about $300) this was satisfying.

Yes there is a torque spec but I dod not know what it is. You have the clymer manual and it will tell you in there.

Roy

[GregFeeler]

The next day I removed the belly pan and the bracket which it is attached to (thank you, Clymer) and discovered that there are two nuts connecting each exhaust pipe to the bike. Of the eight, one was missing. Found a nut with appropriate diameter and thread (thanks, Dad) and snugged it up. I also tightened up all the other bolts while I was at it with a socket wrench and extension to "firm."


I would recommend ordering the correct exhaust nuts for your bike. I believe they are copper plated so as not to seize on the exhaust studs like the (likely) standard steel nut you used will do eventually. They also are "pinched" to have a built in locking feature that keeps them from backing off without requiring excessive torque.

Speaking of that last part, you might consider replacing the crush washer gaskets for the exhaust header. There are four (one for each header pipe) thick copper crush washers that seal the header pipes in the cylinder head recesses where they fit. They are sensitive to being over tightened - if crushed too much they will leak. Yours may still be fine, but it wouldn't hurt to ride the bike and make sure none are leaking after you replace the nuts.

[Ridealot]

+1 on replacing the nut with the correct one. Probably wouldn't be a bad idea to replace all of the nuts with new ones. I had new crush washers for the exhaust header but since the old ones never leaked I never did replace them.

It seems like the locking tab on the exhaust header nuts gets weak over time and mileage. After I replaced the nuts with new I didn't have to retighten them every couple of months anymore.

[98lee]

11627662083 Gasket Ring (C32X40) you need 4 $1.84 ea.
11621744323 Hex Nut (M8) you need 8 $0.85 ea.




:dance:dance:dance

[58058D]

Glad to 'hear' this was solved so easily. My '93 1100RS had one of the gaskets fail while on the road to Denver from the Texas National years ago. Sounded like an unmuffled VW on three cylinders, until the plug finally fouled enough it just quit firing. BMW of Denver fixed it under warranty and off I went with a much quieter and properly firing brick. Indications were that the gasket had probably fallen out of plumb when being installed and worked a while, but eventually failed.

[moondog]

Keep an eye on the flange weld. The K-bike exhaust are notorious for cracking. Repaired mine twice then it cracked again. Replaced it with a Remus.

[kgadley01]

I wouldn't worry about the torque on those parts. but I would use locktite.

[MysticRed]

I wouldn't worry about the torque on those parts. but I would use locktite.

Locktite on a header bolt/nut? Too much heat, IMHO.

[moondog]

New locking nuts and anti-seize goop.

[BCKRIDER]

I can't believe getting so much good advice so promptly!

Roy, you are right about the torque recommendation in Clymer. (p.20, after I measure the diameter.)

98Lee, thanks for the part numbers. I think I will order 4 gaskets and 8 nuts - the price is right - and likely have my local BMW friendly garage (competent and cheaper than the BMW dealership) install them to the correct torque, even if it isn't critical. I can take off the plastic and mounting bracket, at least! Couldn't see any problems with welds, but doesn't hurt to have more professional eyes on the area which I didn't even know was a fairly common problem.

There was one vote for loctite and one against. Also one vote for anti-seize on the threads. Any of you earlier posters care to register an opinion?

Think I'm OK for now to ride, but clearly should not forget this issue, which is exactly what I would have done without your advice. Thanks again to all of you.

[PHMarvin]

New exhaust gaskets if you desire, new exhaust nuts, high temp anti-seize on the nuts and studs, then torque to 21Nm (16ft/lb). Check the torque every oil change. You do NOT want a nut to vibrate off, then the header shift slightly and snap the stud off, most likely up in the head.

[GregFeeler]

I can't believe getting so much good advice so promptly!

Roy, you are right about the torque recommendation in Clymer. (p.20, after I measure the diameter.)

98Lee, thanks for the part numbers. I think I will order 4 gaskets and 8 nuts - the price is right - and likely have my local BMW friendly garage (competent and cheaper than the BMW dealership) install them to the correct torque, even if it isn't critical. I can take off the plastic and mounting bracket, at least! Couldn't see any problems with welds, but doesn't hurt to have more professional eyes on the area which I didn't even know was a fairly common problem.

There was one vote for loctite and one against. Also one vote for anti-seize on the threads. Any of you earlier posters care to register an opinion?

Think I'm OK for now to ride, but clearly should not forget this issue, which is exactly what I would have done without your advice. Thanks again to all of you.


One thing you'll find about this this forum is there is no shortage of opinions. :D As for votes, the correct nuts are designed to work without either anti-seize or loctite. I've never used any on my K's and never had a problem.

[MysticRed]

one thing you'll find about this this forum is there is no shortage of opinions. As for votes, the correct nuts are designed to work without either anti-seize or loctite. I've never used any on my k's and never had a problem.

+1

[jeremell]

It probably sounded sweet, you should just leave it alone. Loud pipes save lives!

[98lee]

Fastners on exhaust systems have two universally in common properties: they come loose when you don't want them to and they rust and seize when you want to take them off.

The design of the nut (slightly distorted) makes it a mechanical lock nut for ONE use. After that, it's locking capability is reduced. That's why they are designed to be replaced.

Loctite is not recommended on any exhaust system because the heat involved is above the temp that Loctite is designed for. In addition, it can make removing problematic exhaust nuts even worse when cold.

With a NEW mechanical lock nut, properly torqued, using a small amount of high temp anti-seize is the best of both worlds. The mechanical lock nut insures that it won't come loose and the anti-seize prevents the moisture and heat from rusting the nut to the stud. It is not required, but could help ten years down the line if you want to remove them for some reason.



:dance:dance:dance

[moondog]

fastners on exhaust systems have two universally in common properties: They come loose when you don't want them to and they rust and seize when you want to take them off.

The design of the nut (slightly distorted) makes it a mechanical lock nut for one use. After that, it's locking capability is reduced. That's why they are designed to be replaced.

Loctite is not recommended on any exhaust system because the heat involved is above the temp that loctite is designed for. In addition, it can make removing problematic exhaust nuts even worse when cold.

With a new mechanical lock nut, properly torqued, using a small amount of high temp anti-seize is the best of both worlds. The mechanical lock nut insures that it won't come loose and the anti-seize prevents the moisture and heat from rusting the nut to the stud. It is not required, but could help ten years down the line if you want to remove them for some reason.



:dance:dance:dance

+1!

[GregFeeler]

With a NEW mechanical lock nut, properly torqued, using a small amount of high temp anti-seize is the best of both worlds. The mechanical lock nut insures that it won't come loose and the anti-seize prevents the moisture and heat from rusting the nut to the stud. It is not required, but could help ten years down the line if you want to remove them for some reason.

Lee, I greatly respect your K-Bike knowledge and the beautiful bikes you ride, but my concern about using anti-seize on these nuts is that is invalidates the torque specifications. Those are set anticipating dry threads, and anti-seize acts as a lubricant and especially in the case of those fat header gaskets, could cause you to over-torque the header studs. Now maybe in a practical sense and in this case, that won't be a big issue - I don't know. But, it's always been my rule to not use any "lubricant" on anything requiring accurate torque settings unless absolutely necessary. You've likely pulled apart more K-bike exhaust systems that I have, so maybe you've seen instances of the nuts seizing. So far, I've not had any such problem.

[moondog]

Lee, I greatly respect your K-Bike knowledge and the beautiful bikes you ride, but my concern about using anti-seize on these nuts is that is invalidates the torque specifications. Those are set anticipating dry threads, and anti-seize acts as a lubricant and especially in the case of those fat header gaskets, could cause you to over-torque the header studs. Now maybe in a practical sense and in this case, that won't be a big issue - I don't know. But, it's always been my rule to not use any "lubricant" on anything requiring accurate torque settings unless absolutely necessary. You've likely pulled apart more K-bike exhaust systems that I have, so maybe you've seen instances of the nuts seizing. So far, I've not had any such problem.

A valid thought when fixing aircraft but on something one can pull over to the side of the road, not a huge issue. I would rather use anti-seize and by-pass the torque and use the "german torque", "good n' tight". I would only be concerned with torque on wheels and engine parts other then exhaust. Heat can have terrible effect on parts and as hot as an exhaust gets stick with the anti-seize.

[TinMan]

OK guys...a little steering for the stupid, here. I am getting ready to replace my crush ring exhaust gaskets on my '94 K1100LT. Which way does the roll crease go, up or down, in the exhaust port?

th:dunnonx

[GregFeeler]

OK guys...a little steering for the stupid, here. I am getting ready to replace my crush ring exhaust gaskets on my '94 K1100LT. Which way does the roll crease go, up or down, in the exhaust port?

th:dunnonx

You want the crease to go up toward the engine to absorb more noise. :brow Actually, I don't think it matters at all. Usually I put them up only because the ridge in the head is broader then the surface of the header pipe and "maybe" that might make for a better seal. Maybe not.

[TinMan]

Thanks, Greg. That makes sense to me.

I hope to put her back together tomorrow. Too many of the fall riding days here on the Blue Ridge going by too quickly.

[TinMan]

BTW, 5 of the 8 studs came out of the head when I dropped the exhaust. Any cautions or ideas about any possible trouble with the re-insertion of these? I was careful to arrange them in such a manner as to insure their return to their respective locations.

[TinMan]

Oh baby!! I found a couple of cracked vacuum plugs on the injector/throttle body...checked all...changed a few lines that showed weathering/cracks. Put her back together last night and it's like riding a new bike, with an extra 1100 cc's. She was fast enough before, she has unbelievable high end torque now.

I love my brick!!:wow

[GregFeeler]

Oh baby!! I found a couple of cracked vacuum plugs on the injector/throttle body...checked all...changed a few lines that showed weathering/cracks. Put her back together last night and it's like riding a new bike, with an extra 1100 cc's. She was fast enough before, she has unbelievable high end torque now.

I love my brick!!:wow

Good on your for finding these things. Time and heat takes a toll on rubber parts. Put it all back together like it was meant to be and your bike should run like a scalded cat. :thumb

[stevenmi]

I wouldn't worry about the torque on those parts. but I would use locktite.

Personally, I never use locktite on exhaust bolts/nuts, but I always use 'Never-seize' on them.

And I am sure your 'firm' is tight enough. These are not technical bolts. You saw what happened when one loosened and failed....it's not like your engine blew up.

'Good on ya for spinning your own wrenches.