The muffler on my Saito 91 will not stay together. The first one would came apart repeatedly until enough pieces were lost that I called Horizon to ask for a solution. They had no idea why it would not stay together but they sent me a replacement muffler. I checked the tightness of the bolt and nut on the new muffler and it was ok, any tighter and something would break. I checked again after a 10 min. flight and it was still tight. On the 4th flight after installing the new muffler it came apart again[>:]
Another call to Horizon and the same story, this service tech said he had never heard of a muffler coming apart but he would send another one to me.

I have had several Saito engines over the years and have never had a muffler come apart until now.

Does anyone know why this is happening? Is there a solution?

rv9-a

I have several Saito engines, including the .91 single cylinder and I have not had any issue with the muffler, even though I now that some people have had the same problem as you. The way I tighten the nuts is when the engine is hot, just be careful and use proper gloves for the task.
Recently I started to use Gasket sealer (the red one) on the threads of the pipe just to avoid the nasty burned castor oil get impregnate onto the outside of the muffler. Engines look better I do not know if this sealer helps to maintain the nuts tight, but as I said I have not had that issue so I could not tell the difference.

Is the muffler mount facing down or up? If up, you are adding a moment to the muffler from the compression/firing stroke. A kick if you will. Try pointing the muffler down (I'm guessing here) and that kind of kick is greatly reduced on the muffler. The back end of the new mufflers are the furtherest out thus are really taking a beating. A ten minute flight at 9,000 RPM is equal to 90,000 hits on the muffler.

Cheers,

Chip