ORIGINAL: kassun
I spent about 5 hours yesterday step by step tuning and trying to get the engine to run but to no avail. As soon as I try to go WOT it sputters and dies and the fuel leaves the line and runs back into the tank and the engine dies. I checked for air leaks and used RTV sealant on the muffler to make sure I wasn't loosing pressure but no luck. MY LHS has a OS .61FX that has been sitting on their shelf for almost a year and the guy dropped the price to 120.00 so it looks like my twist will be getting a boost in power this Friday. Any other Evo owners out their had a similar problem?
Thanks,
Kassun
That sounds like a fuel plumbing problem.
Something is screwed with the plumbing. Higher rpm should mean higher muffler pressure that'd give higher fuel pressure. And that will push the fuel harder, not suck it back in.
It sounds like your fuel pickup might be able to deliver very light flow but sucks closed. Something like grass trash in the needle body can do that. Too long a fuel pickup (the clunk hole touching the tank wall) can also do it. Sometimes, a clunk that's fallen forward can do it. It's hard to predict what's causing it, but it does appear to be something causing a closed off fuel feed. And it only happens under strong fuel draw or faster fuel feed.
Hey, easy test is to rubberband a tank to the side of the nose and see how the engine draws from it. If it still dies, then the blockage is probably in the carb. Trash can get into the needle body when the needle is removed. Balsa dust often gets in, but it usually washes through. I've seen grass in there.