Hi All,

Anyone else had this problem and got a solution to fix it?

Prob is I have crrcpro 55cc engine with a pitts wrap around muffler & what
happens is after 3-4 flights, the bolts come loose.

Using hex bolts with lock tight and it still happens. Everything has been checked
for any balance issues and all is good in that area.

Any solutions welcomed.

Cheers Danny-II

Try this.Remove bolts and clean bolt and hole threads with carb cleaner,reinstall with high strenght loctite(red) and lock washers,immediately start motor and run until at operating temperature,about 3-5 minutes,kill motor and retighten bolts,then let it sit so the loctite sets up.
Jeff Sikes

+1 on the red loctite.

Also, make sure that the wrap around muffler has a metal brace that extends from the muffler back to one of your head bolts. Those mufflers can vibrate the bolts loose and even crack the mufflers if they aren't braced properly.

Hmm...we use heat to remove lockite, even red.

680 red is the high temp stuff if you must.

Cleaning the bolts, lock washers, and snugging the bolts (dont ham fist them or you will just remove the "spring" from the bolts) when its warm and they should be fine.

Remove muffler, clean bolts and threads, put a dab of Permatex Ultra Copper on the bolts. Let it set up for 10 or 15 minutes then bolt the muffler on. After trying different kinds of loctite, running motor to get the temp up and retorquing, etc., the Ultra Copper has been the one thing that has worked. Several motors later, one time application and tighten one time, I've yet to have a muffler come loose. It's made for high temp. I use a thin film of it as a muffler gasket as well. It's good stuff!

make a strap to support the other side of the muffler to the firewall or preferably to the engine. this muffler comes with a strap do it like this

Also make sure your prop is balanced and the engine is tuned properly of you will not keep a muffler on it!! if it has loosened your threads you might have to heli coil them for proper tighting.. good luck its a pain. you can also drill holes in your hex head screws and run some bailing wire through them to each other so they canot come loose.

Dang did we not just have this same thread come thru two weeks ago. ALmost word for word. Just saying.

There was a lot of great advice on that one. i am just to lazy to search and find it for you this morning. Anyone ???

Update;;;;;;;;; i guess i am not too lazy after all

Found it https://www.flyinggiants.com/forums/...+muffler+loose

Danny, do away with the gasket that came with your engine. They tend to compress leaving the bolts succeptible to getting lose.
Instead, wipe a thin layer of high-temp silicone on both flanges.
Clean the bolts with metho, acetone or siimilar solvent and put a few drops of red locktite on them.
Tighten well and they shouldn't come out.
Obviously and like has been mentioned earlier in the thread, you need to support the can of the muffler. I often use the old fashioned curtain springs by wrapping the spring around the outer end of the can a couple of turns and then anchor it to the firewall or better still, to the engine mounting bolts if that is easier

Nord locks... they're fun too

Originally Posted by theKM

Nord locks... they're fun too

Nerd locks?

Don't you need a left handed metric crescent wrench to install Nordlocks?

drill the bolt heads through the side and lock wire them...

Teflon tape (Plumbers tape) Old engine guy gave me the tip in 97 when I had a Q-52 that could not keep the bolts in. Used it ever since on everything for 40cc to 150cc engines and never had a bolt come lose