hi i am new to the forum and am looking for some advice. my friend and i just built a mini sandrail and put an f4i 600 engine in it, came from a running bike. the problem we are having is that when the bike is under load it bogs and falls on its face and wont rev past 4-5k rpm. its almost like a reve limiter. it will free-rev fine but when its in gear it craps out. we've changed plugs, new battery, checked fuel pressure, even hooked up a wideband to it(perfect 14.5-14.7 afr's even when its studdering). we were wondering if you guys had any suggestions?? thanks in advance

 

a/f is a bit high -- 13.2 -13.7 would be a better range for that engine. How much does your machine weigh? If it's heavier than the F4i then that could cause some lag.

 

it weighs about 5-600lbs, definatly heavier than a f4i, but in first gear it probably doesnt have anymore load than a bike say in third gear, but im not sure if there are maps for certain gears?

 

same thing happened to my bike when i almost ran out of gas, would rev free forever. under load wouldnt go past 6000rpm to save my life. but i rode for a good 5 miles to the gas station like this no sweat.