Spark Plug fouling

Hey guys,

I have an XR650L that I had the heads and valve guides re-done new piston and rings installed by a dealer. It worked fine on the ride home at the begining of last winter.

Now that it's spring I cranked the bike up, rode it around and it worked fine for a while now it idles ok but won't rev up, just stumbles when given gas and then dies when I try to give it more gas. I checked the spark plug and it looks like oil is getting to the plug.

I'm really ticked off b/c it's been a while since it's been to the shop so he'll probably say I've messed something else up and won't warranty it. What do you guys think may have happened?


If there was gas left in the carb, it turns into goo that blocks the fuel passages. It might just need a cleaning.

unless you failed to break the bike in properly the rings may nor have never seated and thus the oil blow by and fouled plug. Or, simply the plug is gucky fouled, replace it - clean the carb and try again, I'll bet it runs fine afterwards.

Also you did not mention any mods on the bike, like jetting etc, maybe too big a pilot or main jet and or floats off - making the plug foul out.

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