hey guys i have two saito 4 stroke 100fa engines and with one i'm haveing trouble with the muffler coming loose and just dangling, i've tried lock tight thats heat resistent and everything else but to no avail. on my last flight it didn't come loose for a change it just broke clean of right where the manifold goes into the muffler. so i'm wondering if you guys would have any ideas. i was thinking its vibration from the prop which i've tryed changing too but stil the same problem. the second engine seems to run fine but the valve covers get really hot and the covers on the first engine stay cool. the second engine when you turn the prop by hand has zero compression but seems to run fine and its only a month old. the engine with the muffler problems is a year old and has great compression when turning the prop by hand. so do you guys have any ideas on what the muffler issue could be on the first engine and if the lack of compression in the second engine is something to worry about.

send them in to Horizon if they are stil under warranty, they have great customer service. I had to send in my Saito 125 after the connecting rod broke and they fixed it for free. So if there is a problem they will fix it as long as its still under warranty.

Re: Coming Loose.

I was fighting with this on most 4 stokers...

In spite of conventional wisdom, I fixed the loosening problem with plain old blue lock-tite.

I completely cleaned the threads and receptacle to make sure they were clean and dry.

I applied a few drops of locktite and screwed things down, letting the engine sit overnight.

That solved the loose muffler problem on all of my Saitos.

Re: Compression

You should get a bit of resistance as the prop swings around, assuming the glow plug is in place.

If not, the valves may not be closing fully, and they need to be checked.

This may also be why there is such a difference in the heat you've noticed.

I've also had good luck with blue locktite on 4-stroke mufflers. I've also seen people use the orange high-temp RTV silicone with good luck. they smear it on the threads and lock nut. It just looks crummy in my opinion.

You should definitely check the valve adjustment but keep in mind that ringed 4-strokes don't always have the same compression "feel" when turned by hand as you'll find with other types of engines.

The ring rotates and sometimes feels like there is no compression when they are in different spots?? That's what I found in a couple of mine anyway. I don't use the locktite and don't have anything come loose. I run up my engines until they are hot and then tighten the muffler lock nut again. A valve adjustment would be the first thing I would look at if the engine is running hot. If it is still doing it then I would send it right back to the service center, like beach said, Horizon is very good about doing repairs or replacement, for the price of the engine there shouldn't be any problems at all.

thanks alot for the advice guys.....i never thought of heating the engine first before tightening the nut.....according to physics i guess it should work. I will check the valves on it too.