My '11 YZ has started sputtering at certain times and power settings. It seems to have a pretty consistant low RPM misfire as I slowly roll on the throttle. I've found it will also sputter, sometimes quite badly, when cruising the dirt roads between trails. I've gotten good at replicating the studder my slowly rolling on power, backing off slightly, then slowly rolling on again. When on the trail I don't notice the low RPM studder so much as it actually makes the power delivery a little smoother, but has screwed me when approaching obstacles. When I get the low RPM stumble usually a good whack of power and it pulls really hard to the upper revs. The cruising stumble, is pretty much a big loss of power. doesn't stall, but wont accellerate at all.
What I've done:
It seemed like fuel starvation, so I replaced the fuel pump and filter and had the injector serviced. No changes, still does it
Replaced the air filter and spark plug. No changes, still does it.
Years ago I wired in some lights. I thought they could be affecting the electrical system and ignition. Removed it all and cleaned all the electrical plugs and connections I could find. No change, still does it.
Valves are in spec
Fresh oil and filters
It still starts how it always did, really well when cold and really inconsistantly when hot.
I'm at the point where I think I need to replace ignition components. I just don't know where to start.
ECU, injector, ignition coil, condensor, rectifier, plug wire?
Edited by WouldsAssassin, April 07, 2016 - 02:54 PM.