ZoomZoom-RCU

Was curious, what are the symptoms of a reed valve that needs to be replaced? I'm tweaking an .049 engine thats been problematic in its consistancy....ie..erratic running....seems to rev up then slow down...almost like a pulse. Its still running within ranges fast enough to fly a plane, just the top end seems to waver up and down. I'm sure its not the needle creeping either...its been fuel tubed to be secure. Just curious though cause its kinda wierd.

ZZ.

digital_trucker

Make sure your back plate/tank isn't leaking. Brown paper shopping bags are a good source of gasket material.

burtcs

ZZ:

Do what DT sugested, check for leaks. Silicon sealer/adhesive work well for sealing the engine in a non-destructive way. When this happens to me, the searching/surging rpm thing, I have found that the engine is just a pinch too lean and it will go away if I richen the mixture with the needle valve (just a little)

- Steve B.

NormF

Not sure if we are talking about the same seal, but there is a small, black "O" ring type seal between the rear needle valve back plate and the venturi tube through the tank. Leaks here will cause all sorts of erratic running. You can try cutting a thin sliver of fuel line and put it in place of the "O" ring.

If there is a problem with the reed/dirt/bent etc. my experience is that the engine won't run beyond the prime.

- Norm F

ZoomZoom-RCU

Thanks for the help guys, and Norm, your answer raised a question. Is this the "O" shaped orfice that the reed presses up against that you are referring to? Cause if so......well.........using a homespun vernacular....."there aint no gasket there"....hehehe. Hope so, cause that would be an easy fix. I've just written this motor off as a spare partser for now...as all I could figure was it overhetaed somehow, and blew the compression. This idea of yours might prove my final theory wrong.....much to my pleasant suprise. Everything else has been ruled out.

ZZ.