I have a Big Bear 350 4x4 and have replaced the spark plug and battery but still have weak spark. It causes the new plug to foul. What should I check next? I have meters just need to know what to check and what I should read?

 

Are you sure its a weak spark that makes the plug foul?Most of the time its a wrong air and fuel mixture that fouls plugs.

 

It could be that, the spark looks blue but looks weak, hard to see. Guess i can check out the fuel system and float setting then if that don't fix it come back to spark. Thanks for your help and ideas.

 

In case you dont know how to read your spark plug.you read the plug by taking it out and look at the tip that was in the cylinder.is the plug real black or white chalky looking?Black plug=to much fuel ,not enough air.White plug=to much air ,not enough fuel.You want that plug to be brownish color.some suggestions:is air filter clean,what size fuel jet,air leaks around carb or intake

 

I dont know anything about a Big Bear, but I do know my buddy has a Polaris, and last week his bike wouldnt crank because of a weak spark. Turns out the rev limiter was bad and was engaged all the time. We bypassed it by unhooking it and now its fine. If yours has the parking brake rev limiter switch at the hand brake, I would check those first. Sometimes they get stuck with mud/dirt. Hope this helps. I know those electrical problems can be aggrevating!

 

Ok, I have gone though the carb and cleaned, rebuilt and adjusted. Still have the same problem. Now I see what appears to be weak spark while cranking (is is blue spark but very hard to see) and I can get it started when cold and it idles until it warms then dies and won't restart. I pulled the plug when it's warm and won't restart and i do not see any spark. Does anybody know what the coil should read with a digital meter on ohms? Does this sound like the coil or some other component? Thanks for any help.

 

Do you know what the factory letters and numbers for that bike is?Example:YFM350.I have a book with several atvs in it but I dont knowwhat the exact letters and numbers for that one is.

 

I found a book with the info. Mine is a 1996 YFM350FW. I ohmed the coil and readings came up high with the spark plug cap on and normal with the spark plug cap off. I have replaced the spark plug cap and this fixed my problem. I have good strong spark and starts and runs fine. Why is that little spark plug cap $25.00? Whats in it that is special? Thanks for all the ideas and help. Problem seems to be finally Fixed![img]i/expressions/face-icon-small-smile.gif[/img]

 

i have got a big bear aswell mine also had a weak spark i changed the cdi,coil,rectifier and cleand all the wire connections and it was still weak it turns out it was the generator stator hope this helps