500 misfire problem
I see it's a long time since anyone wrote in this thread, but has anyone found a solution? My '98 500 does the exact same thing, when running at more than 3/4 throttle, it starts caughing out the carb and misfiring. I have had the cylinder head off and rebuilt it with new cam, lifters, springs, valves, you name it, and I had high hopes for this, but it did not work. I have played with the carb, cleaning it out several times, making the mix leaner and richer, but no luck. By coincidence, I started it without the air filter box, and then it ran even at higher revs, but it blew out of the carb. I have tried adjusting the timing (cam) in both directions, no luck. I have also adjusted the ignition timing, no luck... The spark plug is new, but I will try to replace it again for another brand (think it is Champion sitting there now, so it should be good stuff). I will also try to run a higher octane fuel (I'm from Norway, and we still have 98 octane at the pumps here :-) ) I'm running it at 95 octane now, but my idea is that higher octanes require higher compression before it ignites. I've done quite a bit of research on the web, and this seems to be a common problem, so SOMEONE must have found a solution. Please help, I'm desperate!!!