So I have this '97 Ficht 150 that I bought it as a leftover in '98. It ran good for 8 seasons (with a false alarm for "water in fuel") then I started having some issues in the summer of 2006...missing at full throttle. I rebuilt the lift pump after checking pressures and finding some erratic needle movement. I hooked it up to my laptop and ran the static tests and diagnostics software and found no indicators of anything wrong. It ran slightly better for a couple of trips...with some pinging. Later, I disassembled the pump and found the checks were distorted. Thinking that maybe I screwed up when rebuilding, I ordered anther kit and rebuilt again...same thing...a trip or two and then running even worse. I also found sparks flying off of my wires during this period so I replaced my plug wires. It still wasn't running right so I bit the bullet and got a rebuilt ECU from DFI Technologies hoping that there may have been more wrong with the ECU than just the false alarms...nothing! Finally we figured out a major issue...turns out that there were two fuel pumps used on the '97 models....one rebuildable and one not...Of course, I had been rebuilding the NOT one! So I replaced the pump with the newer (rebuildable) pump and everything was almost back to normal....almost. It idled very low when cold and I seemed to have lost some top end, and it still pinged here and again. I called DFI to see what they thought and they said that they didn't think it had anything to do with the ECU. I ran it all of last year with these two seemingly minor issues. Toward the end of the season, I decarbed and the next time out It started thumping bad. I did a compression test and found 2 low cylinders...pulled the heads and found 2 cracked pistons. So my winter project?rebuild my motor. Now, I have good compression, good spark, good fuel pressure, and its still running low RPM's when cold. I don?t know about top end because I'm doing the break-in. I called DFI and they graciously sent another ECU to rule out the ECU being faulty...it ran the same. If hard starting is the only issue?I can live with it but I'm afraid that whatever is causing this may be the reason for the cracked pistons. Any ideas???
Also where was the piston cracked?? wrist pin area?? or skirt?? Do you have the grey spark plug wires as old style will cause RF issues and cylinder missfires. Check flywheel sensor for correct measurement. Sound like you have a temp issue and EMM is still in cols start mode running rich. The Follow also could be you knock/ping problem: