I mentioned in an earlier post to tighten the bolt holding the muffler together, and this brings up a modification that I do to OS mufflers. When I started flying I had 2 bolts holding the muffler together break while flying, and the back half of the muffler falls off in flight. Trust me, they are impossible to find when they fall off. You cannot purchase just the back half, you must purchase the entire muffler assembly. So I have a couple of modifications that help prevent this from happening.

The first modification is to use lacing wire to retain the back half of the muffler. As you can see in the pictures attached that the wire goes around the muffler. Very very important is to twist the wire so it is TIGHT around the muffler body. When you do this it prevents if from rubbing on the muffler. Then take the wire down twisting it along it's length and wrap it around the exhaust manifold. Then twist on the other side, cut off, and fold the piece under the manifold. What this does is hold the muffler half on until you can land if the bolt does break while in flight.

The second modification is to totally replace the bolt. I use 6-32 all-thread to replace the bolt. You will have to drill out the holes on each end of the muffler for it to fit. I use METAL self locking nuts (DO NOT USE NYLON, they will melt) to bolt the muffler together. If you can't find metal self locking nuts you can a double nut on each end of the muffler. The double nut will lock in place, put a little blue locktite on to keep it in place. By using the all-thread you won't have to worry about it breaking.

I hope that this helps others from losing half of their mufflers.

Ken