ATV Florida Forum

I'm not sure whats going on with my bike...hoping someone here can help.  the bikes an '04, I'm guessing maybe 40 hours?  it hasn't been ridden a lot, and most of the riding has been with family, so not hard...maybe 8-10 times running moderately hard.

It had been running great all along...about a month ago I did the cam mod as well as check the valve clearances, the clearances were on the tight side of the recommended range, so in other words, still like new (like I said, the bike has maybe 6-10 hours in total running moderately hard).  I also dropped in a powernow valve on the intake side of the carb at the same time.  I ran the bike for a couple hours and it ran great...i was amazed at the difference the mods made...these are the only mods on the bike.  The next time out, it started the popping and sputtering, primarily when I was on the throttle hard in the 1/2-full throttle range.  It would also hesitate maybe 1 out of 3 times off the line when rolling the throttle, it would pull strong until about 1/2-full throttle until it would start sputtering again.

I took the carb apart and cleaned it thoroughly/blew out all the jets with air and reinstalled, and I also swapped out the plug.  Below is a pic of the plug.  Spark seems good, I'm getting a strong spark that will jump a good 1/2" gap.  My next step will be to check/clean all my electrical connections, but I'm really at a loss to what's going on.  I can take apart and reassemble just about anything, I can read manuals, but I stink at troubleshooting.  I'm not sure if I have electrical, fuel, or air problems going on.  If it will help, I can try taking a sound clip of what's happening.

I'll also post this on the other site for the people that don't frequent here. 

The plug looks a little rich. If you roll on the gas easily will it accelerate without hesitation? If so I would try to drop the needle down.

See if the decompression plug has come out.. Its common for 04-05 YFZ450s