Lately I have had a problem with fouling plugs in my LT250R. It has just started doing this. I ran on the same plug for about 3 weeks then this weekend I went trough 4, about 1 every hour. I know it needs to be jetted, it is extremely hard to crank at first, but it has just started doing this and I have been riding it like it is for 5 months. It was rebuilt in October and I have been runing Motul oil at 50:1, it shouldn't need a rebuild. Will adjusting the little air screw on the carb do any good? Could it be the jetting? Has any one else had this problem and know how to solve it? Any input would be great, thanks.

 

A fresh motor should never be hard to crank (unless your talking about some serious compression) but they should always start with a few kicks.

Sounds like your jetting is way off if you're fouling plugs. The carb might use a good cleaning as well. Was it done with the rebuild?

Also, a change in the oil you are using can goof up your jetting.. Have you always used Motul?
The small air screw on the side of the carb is basically for the idle circuit and just off idle.

I'd suggest doing some research about jetting here on the net. Mikuni has a good website along with others regarding what jets influence what, and how to do basic jetting.
always watch your plug color, because too rich is way better than too lean. (kaboom)

Good luck

 

Some one with a similar problem with starting was told to go up a size on the main pilot jet. I'm gonna go through the carb, get a new filter, and by alot of jets to play with to see if I can solve the problem. Some body else told me a weak spark from a bad stator may cause it to foul out, but I believe it runs to good for that. Runs great, just eats plugs like candy.

 

I have run Motul since its rebuild in October. Always 50 to 1, it has just started the plug thing. Just needs some tweekin I hope.

 

It could be carbon on your piston, if youve been running it rich, the deposits could make it hard to start also.