Muuffler head to the engine.. need help. PICS!

J

jordanmalmal

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Hey guys,
This may be a stupid question, but if I don't ask it I won't know...
I was riding home on the trails and my bike started making noise right under the gas tank on the engine, so I looked underneath while the bike was still on and it was coming right out of where the muffler goes into the engine.
A nut came loose and the other just fell off while I was riding..
I've never seen these types of nuts before, but then again I am new to actually working on engines.
So my questions would be: Where would I find these types of nuts? (home depot? home hardware? Canadian tire? Or would I have to order some from a bike shop? Could I use a different type of nut with some Loctite so they don't fall off again? I'm sure there is an O ring of some sort, what type of thing do you look for to see if the ring has been damaged, other than the obvious..
Thanks guys!

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I would strongly recommend that you order the correct replacement part from the dealer and order a new exhaust gasket.

The threads are an ordinary ISO (i.e. metric) size, which means an ordinary metric nut (probably M6x1.0) will fit on there, but the cap on the end that covers the end of the stud is there to stop corrosion from causing the nut to seize to the stud. That cap needs to be the correct length, otherwise the cap nut will bottom on the end of the stud before it actually clamps that flange in place.

There is a copper gasket between the end of the exhaust header pipe and the cylinder head, but unless you rode for a long time with it leaking badly, OR if you reefed on the single remaining nut in the hope of keeping it in place (and thus applying force unevenly to that gasket and distorting it) you should be able to re-use it.

I'd try snugging the new nut in place to see if the original gasket holds. If it does, great. If it does not, you will have to replace the exhaust gasket. Undo both nuts, you may have to undo some other part of the exhaust system to allow it to move away from the engine, get the old gasket out and slip the new one in. If it won't stay put, use a dab of grease to hold it (and don't be surprised if this causes smoke from the exhaust for a little while).

It's not uncommon for the exhaust gasket to seize to the cylinder head ... you may have to pry it out. Be careful, pry on the gasket without damaging the aluminum cylinder head. This is not a job for a gorilla.
 
Brian, your advice is usually right on, but in this case I suggest the acorn nut shown is merely decorative. Use a regular nut of the correct size and pitch with a lock washer and be done with it.
 
I'm no expert, just a backyard wrench, so nothing I say is carved in stone.

I'm not certain if loctite is effective in higher heat applications such as this. In any case, I would use it in addition to a mechanical locking device, such as a lock washer or a serrated flange nut.

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Jayell said:
Brian, your advice is usually right on, but in this case I suggest the acorn nut shown is merely decorative. Use a regular nut of the correct size and pitch with a lock washer and be done with it.
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I would think they use an acorn nut there to prevent it from seizing due to rust on the open end, but rust is just free loctite right?

Either way Im a fan of replacing parts with the same kind of part. Id probably use a regular nut in the mean just to keep riding till the correct replacemnt comes in, but I would order the OEM acorn and replace it eventually. Your probably only looking at $3-5 per nut from a dealer
 
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JohnnyP636 said:
I would think they use an acorn nut there to prevent it from seizing due to rust on the open end, but rust is just free loctite right?

Either way Im a fan of replacing parts with the same kind of part. Id probably use a regular nut in the mean just to keep riding till the correct replacemnt comes in, but I would order the OEM acorn and replace it eventually. Your probably only looking at $3-5 per nut from a dealer
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Sounds very logical.

I understand both sides, and I would agree with both sides.

I think that ordering the same nuts is better for me in the long run, but if I want to keep riding (this month) I should find the same pitch and thread nuts without the acorn... I will still be able to ride, and when the replacement ACORN nuts show up in the mail I will replace them.

As for doing damage to my engine.....?
 
Remove the last sad acorn nut and run it up known metric threads at the hardware store until you hit pay dirt. Then maybe run double nutz for the faux acorn effect? Engine damage? Gaps at the head/pipe interface is not good for either mating surface.
 
personally, ide just get a OEM one for the sake of not having to look up the right threading.
i know when i did the exhaust on my honda it was cheap to replace them. i want to say it was under $1 each.

otherwise go to a actual nut and bolt shop similar to brafasco (but they have a $10 min purchase)
 
half the time if you wanted an exhaust stud to come off , it breaks the stud and you've got a mess to fix, his just falls off on its own and hes still not happy.
 
^ Truth!

FYI to get the bike back on the road, if I couldn't get the proper acorn nut in a hurry, I'd use a flange nut (photo in post #5) temporarily until the acorn nut showed up.
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