Fouled Spark Plug

[CRAZY_CARL]

Last weekend I was leading my race with a good lead than I fouled my BR9ES. So I went to the pits where I borrowed a buddies BR7ES, in which I didn't foul for the rest of my 2 hour race.

My question is, what is the best plug for low speed riden where its low in the RPMs? I had no problems with the BR7ES, so Im thinking I should stay with this one although I am unsure what I should do.

Thanks for your help,

Carl

[yathump]

What bike?

If your jetting is dialed in you shouldn't have any fouling problems, no matter the type of running

[USED YZ426F]

If your jetting is dialed in you shouldn't have any fouling problems, no matter the type of running

+1

As long as your engine and ignition are working properly, you won't have a fouling problem with proper jetting.

Changing plugs to a hotter heat range may prevent fouling, but it is not the correct answer to your problem.

[DLHamblin]

What bike?

If your jetting is dialed in you shouldn't have any fouling problems, no matter the type of running

If riding MX or similar then I agree, but if riding slowly at low rpm's a 1 step hotter plug may be needed even with proper jetting (the OEM plug heat range is aimed at the target use of the bike; vary from that and you could need to go up or down one step).

But I fulley agree it should not be used to mask bad jetting.

I am also curious what bike, as he went two ranges down. If it was a 250 it likely should have been using a BR8EG anyway which also may not have fouled. If it was a 125 I'd be leary of running a BR7ES (at the least pull it after a bit and check to make sure its not running too hot).

[CRAZY_CARL]

Sorry its a 2004 YZ250...

So I should take it into the shop to get it properly set up than?

[breedlove23]

Sorry its a 2004 YZ250...

So I should take it into the shop to get it properly set up than?

I would take a peek at your jetting first before dropping money down. Make sure you are jetted for your mix, temp, altitude, and conditions. Just do a search you can spend weeks looking at jetting thoughts and ideas.

[yathump]

Sorry its a 2004 YZ250...

So I should take it into the shop to get it properly set up than?

Don't take it to a shop, read the jetting sticky up top, break it down between the airscrew/pilot jet-jet needle and your main jet and adjust, over 1/2 the fun is the learning process

[mx730md]

put in the right br8e -stock plug

then check your pilot jet it might still be the stock 52 or 55 i would swap it out for a 48 and if your still fouling you could go to a 45.

also what oil are you using and at what ratio are you runing .maybe your runing it lean and not making enough heat to burn the oil of the plug

[CRAZY_CARL]

Im using Amsoil Interceptor and Im mixing my oil at 40-1. I will go to the shop this week and swap my main pilot jet for a 47 and hopefully that solves this problem.

Thanks for your help

[mtrablue]

okay, slow down here. you have a main jet and a pilot jet, not a main pilot jet. the pilot jet does not come in a "47". there is a 45 and the next size up from there is a 48. go by your local discouont auto parts dealer and pick up a couple NGK BR8ES plugs. they will be cheaper than at the bike dealer. the "G" model is a waste of money. fresh plug and a 48 pilot jet and you'll be on your way. by the way, as the earlier post said, check the jetting sticky and learn about your bike. they're magic when they're jetted right.

[mdkcrf250r]

put in the right br8e -stock plug

then check your pilot jet it might still be the stock 52 or 55 i would swap it out for a 47 and if your still fouling you could go to a 45.

also what oil are you using and at what ratio are you runing .maybe your runing it lean and not making enough heat to burn the oil of the plug

its not the pilot jet...pilot jet controls idle-1/4 throttle...I dont know about you but I'm in that range about 0.1% of a motocross race...I'd put my money on a leaking trans side crank seal...

[mx730md]

its not the pilot jet...pilot jet controls idle-1/4 throttle...I dont know about you but I'm in that range about 0.1% of a motocross race...I'd put my money on a leaking trans side crank seal...

ok why dont you read what he said