lose the muffler
 

I have a Stihl 27cc conversion on a ultra stick lite 120 and although it flies great, it will not pull out of a hover or even hold a hover for more than about 8 seconds. My question is... If I fly on private land (no noise restrictions) could I try running with no muffler? I am nose heavy as is and could desperately lose any uneeded weight. I fly at a hunting club and there is no one else to disturb, and I have earplugs;)

RE: lose the muffler
 

Running with out an exhaust will cause any 2 cycle to run lean and burn a hole in the piston.

RE: lose the muffler
 

Muffler or no, running lean is caused by the reluctance of some pilots to ever touch the carb needles..:eek:

We run our methanol GT80 racers at 11,500 rpm with only a 1 inch stack to keep from burning holes in the cowl..
Only hole I ever saw in a piston was a Q75 race engine running about 50% nitro in the fuel...Couldn't get it rich enough....The carb fuel passages weren't large enough....[8D]

RE: lose the muffler
 

There is a difference between Gas and Methanol.

Gas runs much hotter and will burn a piston.

RE: lose the muffler
 

I have heard of 4 stroke car engine burning ex valves from blown header gaskets but I didn't think a 2 stroke would have any problems. Maybe the piston pulls air from the open port on its downstroke? Anyway, I have another question, Is there such a thing as having too much free flowing exhaust on a 2 stroke. How do you go about getting a tuned pipe for a conversion? (Stihl) This is a cheap conversion anyway, I think I may leave the muffler and take my chances by running a little on the rich side.

RE: lose the muffler
 

Lose the muffler if you're sure you won't be bothering anyone.
It won't hurt the engine in any way. Just be sure to tune it right- and wear the earplugs when tuning it.
A short stack like RCIGN1 mentioned would be the best thing to do.
The general rule of thumb I go by is if you can't run a tuned pipe on a two stroke then go for least restriction possible.
Heaven forbid it will be LOUD though.

RE: lose the muffler
 

The Q75 with the holed piston was running methanol and 50% nitro, just not enough fuel flow...
The stock GT80s run gasoline and Zenoah oil with 8 inch straight pipes, no restriction at all..No holes either...Running one of these too lean sticks the piston in the cylinder way before any hole burns in the top..I guess it's possible, just haven't seen one...
Our exhaust temp on the 289 methanol racer is 900 degrees measured in the air at the flange and have been run at 1000 degrees on the dyno with proper cooling...About 350 on the cylinder head at the spark plug.....
A Mac's Products generic pipe for 30cc engines would work fine, probably get 1000 more rpm, it does on a G26...Costs more than you paid for the engine in the first place, over $100:)

RE: lose the muffler
 

In stead of loosing the muffler, hollow it out and run 2 out lets.
You have lost most of the weight and still have a free flowing muffler.

This really helped a chain saw I had worked over.

RE: lose the muffler
 

try it without the muffler long enough to see if you get the response you want if so I will build you a non restrictive muffler . make sure you richen the engine up so it will not run hot .

RE: lose the muffler
 

thanks Ken, I'll do that