I have a Seagulls 260 Extra with a Saito 100 on it. My question is how do you keep the muffler tight? I have already balanced the prop(s) with a good magnetic prop balancer. The cowl is not touching it anywhere. I have put a new pipe and muffler on it really tightening it down really good with blue loctite on it. I have even tried a big dollop of JB Weld to hold it on. Nothing seems to be working. A new muffler assembly will, if loctite is used on muffler and jam nut, stay tight for two or three flights but, then it will works loose. After it works loose one time you get one flight out of it then carry it back to the shop clean every thing up good with alcohol and try again after going through the loctite process . Then one more flight. Mufflers are 30 bucks and that will only get you 2-4 flights. That is too expensive. I have other engines I have never had this problem with. This is my first 4 stroke. Are they all like this. Before I say I'll never own another Saito or four stroke for that matter is this common with all of them?????

Try tightening the muffler when the engine is hot, it worked for me when I still had my saito.

My problem with my Saito 100 muffler is losing the back half, you can't buy that part alone and have to buy the entire muffler.
After buying 3 mufflers I finally decided to drill a small hole through it and saftey wire it to my firewall.

I haven't tried tightining it while it was hot. I'll give that a try tomorrow. I'm not losing it either. The pressure line keeps it from spinning all the way off. I don't have problems with it comming apart, just loose. When it's loose it dosen't keep enough tank pressure to run properly and if you run it loose for just a short while the header pipe which is hard steel ruins the threads in the aluminum muffler.

No point using Loctite on the exhaust as you use heat to loosen joints locked with loctite. You need to oil the threads on the muffler and header before installing and tightening and re chech while still HOT.

Cheers

use two locking nuts one to lock the other one in place.

Try also Teflon tape.

I'm not impressed with Saito engines, their good qualities are offset too much by their bad ones the main one being vibration. I have two Saito engines and they both vibrate excessively. I'll buy OS next time.

My Saito loosened its muffler this weekend but Teflon tape seems to go the longest in keeping it on.

That's what I use with my 4-strokes. A few wraps of that and some elbow grease, and I have no problems.

The main issue with saito's vibrating is low end tune. They come very rich from the factory. After a gallon or two, you should lean up the low end. It will purr like a kitten after that. I have no issues at all with my saito's, which range from .56 to 1.25. Now, the 1.5 and up, yesthey will shake, but any large single cylinder engine will shake.

NOPE. I have fiddled with these engines all summer; adjusted needle valves, valves, changed props, balanced props, changed fuels, have put multiple gallons of fuel, some 30%, through them, new plugs, and other things I can't think of at the moment. My low end needle valve has been turned in and out more than all my other engines combined.

I have printed out tuning guides and followed them to the letter. I have spent more time frigging with these engines than I have flying them. The 1.00 Saito vibrates at midrange and the covering "drums" so loud everyone at the field comments.

I'm thinking the few ounces of weight saved with a Saito maybe be detrimental if you don't put them on planes with more mass than slabs.

I know lots of people have smooth running Saitos but it isn't me. Thanks for the comments tho...

To try to stay on topic, the Teflon tape works the best (for me) to keep mufflers on.

I do believe my comment was RIGHT on topic, as it was a suggested reason for saitos to vibrate and loosen mufflers.
Blasting saitos and suggesting one should buy OS instead is definitely off topic.
to the OP (ABELL), try tuning the low end if you haven't already. If you get it in tune good, it is more than likely going to quit vibrating so much that the muffler loosens. Also, tighten them while hot. If not, then when they heat up and expand, sometimes this causes the mufflers to loosen.

thanks guys I'll give all this a try and get back with you ABell