ORIGINAL: carrellh
ORIGINAL: Not24
Of course the engine was re-tuned for each prop. The low end should not need adjustment because there is no difference in load at low rpm's. The high end will need adjustment with different props, and that's what I did.
The low and high end needles are related, so I wouldn't totally dismiss the idea that the low end might need a slight adjustment. It is easy to do and costs nothing. If it doesn't help, at least you've eliminated another possibility.
Come on people! Of course the two needles are related, and adjusting one means the other will need a little bit to be perfect. HOWEVER, when an engine runs on one prop and quits on another, just one size smaller, there is something else wrong besides a tweak on a needle valve. If that were the case, all engines would quit unless you got both needles exactly right. There is a range of adjustment where the engine should stay running, and either be rich or lean. If a needle is so sensitive as to need to be exactly perfect, then there is a problem somewhere else. It could be back pressure, fuel pressure, nitro content/compression ratio, etc. You see my point? In my opinion, backpressure on a two stroke is bad for performance. This engine requires fuel pressure to feed the carb properly. It is my theory that these two factors are in conflict with each other. In order to remove the back pressure, I will need to find another way to create fuel pressure. The pump will do that. Going to an open unrestricted muffler will keep from choking the engine, and pumping the fuel to the needle will give constant pressure in all conditions. Call me stupid, but I think it will work.