92' CR250 keeps eating spark plugs
I wonder if I could pick your brains, as this problem I have is driving me crazy!
I've got a 92' CR250 which is great except it keeps eating spark plugs. It tends to eat them every 30-45 mins of riding, but when I pull them, they are still new looking with no damage whatsoever, whowever the spark traces around the electrode & ceramic base. I've gone through 3 plugs now (BR8EG & BR9EG) & I'm on my 4th in 2 weekends.
Now, 2 sundays ago I spotted fuel pouring from my carb overflow & no ammount of tapping the float chaber would stop it, so I went home & stripped the carb to find a load of crap in there.
Carb cleaned, I fired her up & went back out & it ran for over an hour, stopping & starting no probs untill I fell off.
Started it up this sunday gone & it ran for around 5 mins then it stopped. Changed the plug again with a new BR8EG & it went 1st kick. This time it lasted for a good hour & didn't pack up, but I was riding around a tight 1st & 2nd gear circuit wheras we usually ride through woods & fast tracks etc. The fuel leaking has stopped since I cleaned it by the way, so I don't think this has anything to do with the problem.
The bike is fitted with a FMF gold series pipe with what looks like a a 'Bill emins?' signature on it. I presume it is jetted to suit this pipe as when the plugs are pulled they are golden brown. I run the pre-mix at 150ml of silkolene oil to 5ltrs of 97 octane unleaded.
The only other thing I can think of is a faulty coil (something I've heard CR's suffer from, is that true?) Should I replace the coil (£50ukp) for safetys sake or risk breaking down again? My freind whom I ride with had a similar problem on his 96 RM 250 & a new coil cured it, even though the shop who tested the coil said it was fine.
It's a pain breaking down all the time & having to replace the plug & head home.
What do you think it could be?
Many thanks in advance,
Gwaredd Steele, Wiltshire, U.K.