I have a 1999 xc 700 sp. It was running fine and suddenly
went to one cylinder.Thought had fouled plug.Noticed gas
coming out of carbs.Left side seemed worse.Carbs are hol
ding seven to ten pounds of pressure.both cylinders have
110 pds. of compression.Sled has 3500 miles on it.Crankcase
and air box fill up with gas.Carbs have been apart several
times, seem to be fine.Put back together runs on two cylinders for a couple minutes and fills up with gas *again.
any suggestions???

i would take a look to see if the skirt was not broke on a piston

So you are saying the carbs are holding pressure but the crankcase is still filling up with gas. *Have you checked that the floats actually float and have the correct height setting and are moving freely. *Because if the floats are hanging up and not closeing the needle and seat assembly this will happen and fill your engine full of gas. *Also check that none of your reeds are broken.

Bad fuel pump or bad primmer or stuck choke. Don't worry about some gas spitting back from the carbs while at an idle as this is normal. Filling the crank with gas is not normal and would lead me to believe you have a ruptured diaphragm in the fuel pump. There was a recall on the fuel pump primmer. Was that ever done on your sled?

xltboy

I would say the fuel pump is bad for sure or have you checked the float in that carb.