plug fouling problem unsolved
 

it has been going on for almost a year now that my 300 2009 behave badly. it is jetted lean ;PJ35 / 172 CCK needle with clip all the way up and still manage to foul a BPR 5 ES within two hours!
no it is not burning oil from gear.
and the exhaust valve is clean and working.
also it would not rev just like if a rev limiter was on.
i followed the advise from one of the forum threads and adjusted the float height still no improvement.
don't really know what to do any more it does not sound electrical because a new original 8 plug will cure the problem for a few hours only.

Why are you using a 5 heat range plug?

coil could collapse on extended use. 5 heat range is good for burning holes in pistons.

are the plugs on the new bikes supposed to be a 5 range? i run br8 plugs in my 03?

Hes running a hotter plug( 5 ), to try and counter the fouling. Iv never heard of running a BPR plug though, I only use BR8EG plugs in my bikes.
Also what octane fuel and what 2T pre mix at what ratio are you running?

I had a rich bottom end and doing searches I came across the solutions below. The slide change worked for me, cleaned up the whole bottom end, couldn't even get it to idle for very long with a 35 pilot and air screw nearly 4 turns outs. With an 8 slide I had to increase to a 38 pilot and have the air screw at +/- 1-1/4 turns out, idles all day long

Float height
Vent lines blocked
O-rings in the jet block passing (fuel by-passes the pilot jet)
Slide changed from a 7 to 8 this cleaned up the whole bottom end, had to increase from a 35 to 38 pilot jet.

I had a rich bottom end and doing searches I came across the solutions below. The slide change worked for me, cleaned up the whole bottom end, couldn't even get it to idle for very long with a 35 pilot and air screw nearly 4 turns outs. With an 8 slide I had to increase to a 38 pilot and have the air screw at +/- 1-1/4 turns out, idles all day long

i know it was a bit silly to try a 5 plug but in search of a solution..it did not even rev properly anyway.the slide is probably the last thing i did not try. the mix is good the octane is ok since i add octane booster and the base gasket is a standard .25 mm.
in the caribbean it is not easy to machine the cylinder head but i don't think it is that bad for a new bike my 250 had the original plug for 5 years and works like a champ.

Sounds like a choke issue.

MAybe a stupid question but are you using a BR8EG or a B8EG? Some ignitions need that resistor plug to work properly. My old YZ would foul regular B8's but I'd get all year out of a BR8.

Here is a link to my issue I had. Might help might not.
http://www.gasgasrider.org/forum/showthread.php?t=7635