I bought a Webra .50 on ebay, It has a clamp on muffler that consists of two parallel pipes roughly 3/8" in diameter with small holes near the ends and a pressure tap for the tank. It starts fine but after a minute or so it just quits , restart...same thing. When it gets good and hot...nothing!! Any ideas on what might be going on here?
15% nitro in case you are wondering.Thanks , Steve
That much nitro is usually not a good thing for a stock Webra. However, I doubt that is causing the problem you describe.
Check the muffler pressure nipple on the "muffler" to see if it is unobstructed. That could cause the problem you are describing.
Do not load this engine down with a prop larger than a 10x6 or 11x5. Webra engines are designed to rev up. They do not take kindly to being lugged down, especially with high (for a Webra) nitro fuel.
Good luck.
Ed Cregger
Pitts style mufflers are notorious for making good engines go bad! Many of them are designed with far too little internal volume so exhaust purging is poor at best. Any time you have problems with an engine using a non-standard muffler, it is best to return to stock and see if that is the problem.
Ok, now you have my curiosity aroused, care to expand on this internal volume thing a little??
bob
The expanding gas from the combustion needs a certain amount of volume to exit into. If the volume of the muffler is too small, you end up with incomplete and unreliable scavenging or having outlets on the muffler too large to be reasonably quiet. Many pitts style mufflers have much less internal volume than the stock mufflers. Many stock mufflers are a bit on the small side. The closer to optimum you get, the better the engine will run. That is why you can bolt on a GMS 47 muffler on to an OS 47FX and get a good performance increase. It has nothing to do with tuning since the muffler is far too short for that purpose. It is the same with the mousse can pipe. These muffers have nearly ideal internal volumes for the engines.
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