Hi,

I am having problems with cold foul plugs. When hot, the bike never fouls a plug.

The Pilot Jet is 35 (Keihin).

Any ideas how to fix this problem ?

Thanks

cold fouling plugs doesnt make sense. when an engine is cold it runs leaner due to the air charge in the cylinder, carb and air box is cooler and more dense. as the bike warms up, itll run richer as the opposite happens.

do you run it on the choke for a long period of time? how regular do you use you bike? which premix oil do you use?

possible causes imo could be:

running it on the choke too long

the premix has been sat in the tank for a long time and its separated, possibly the fuel in the carb has evaporated leaving the oil residue in the crab resulting in a greater oil ratio when you first start the bike.

maybe the oil your running isnt very good, i used to use PJ1 goldfire and i fould plugs left right and center(on my cr 125), now i use MX7 and ive never had a problem in any of my mx bikes or my trials bike.

another possibility is your running the wrong temp range of plug and the plug isnt coming up to temp quick enough.

if all else fails, rejet the carb.

Tim.