I was wondering if anyone has any experience using a hotter plug in the 610, I am experimenting using a B4 instead of the colder B5, it does fine as long as we run it hard, but if you are just easing around the plug will eventually foul, the mule is new with close to 50 hrs and all the recomended break in servive has been done

 

what does plug look like when ur run it hard,and shut it off and pull the plug, sounds to me like a carb issue but check plug after running it hard and then lets see what it looks like

 

after running it hard the plug looks ok, (but just ok) I also checked the carburetor and it's settings, and it runs fine, at least untill the plug starts to foul out, I don't think it's the carb or jetting, (although I wouldn't rule that out) it's my belief the factory spec heat range is too cold of a plug and was looking for feedback from anyone who had experienced simmilar issues with the 600 series mule or have tried a B4 in theirs

 

Why were you using the incorrect plug to begin with? I'm assuming your engine was still stock at the time this was posted?