Wednesday, 22 July 2009
Misfiring. Anyone got any ideas?
I've just spent three hours and a 250-mile round trip trying to sort a misfire on my Wood Rotax racer. I went to see fellow racer, Anthony Brown of Co-Built, who had a full Rotax electrical system that he assures me was all good. We changed every component individually and methodically.
Coil, ignitor box, stator, pick, plug, HT cap... We disconnected the killswitch. We checked the carb and rubber. It misfires badly at half to full throttle. It starts and ticks over beautifully.
On the way home I thought it might be a kinked fuel line, but the plug is sooty black - which I think points to lots of fuel but a lack of spark. It also shoots the odd flame from the exhaust when it's misfiring which leads me to believe it's spark, not fuel. This bike has run well, it's not like I'e built it up and it's not set up.
The only thing we didn't change was the flywheel itself. We didn't check the valve clearances, but I adjusted them before my last
race and the problem occured the same both before and after that race.
Any ideas? Please... GI