2000 YZ125 Fouling Plug During Warm Up?

Jeffack1

Member
Jan 7, 2003
25
0
I have a stock 2000 YZ125. I have the clip in the third position, 350 main jet and standard needle. Air screw 1.5 turns. During the last week, I have been riding at sea level with a temperature of 70-75 degrees and the bike has been running very good. I have been using a premix of 32:1.

The only problem that I have been having is when I start the bike up for the first ride of the day, the bike will start up (without choke) on the first kick and then I can not get the bike to rev up. It will idle, but will not take any throttle without bogging down. I have tried to let it warm up on idle while giving it short blips of throttle to clear the plug, but after a 30 to 45 seconds, the plug fouls out and that is it. Switch to a new plug and go riding the rest of the day without any problems at all.

This has happened to me three times during the last week of riding. I have been using a NGK BR9EG plug.

Any suggestions on how to fix this would be much appreciated.

Thanks,

Jeff
 

BooBoo

Member
Dec 28, 2004
31
0
You need to go leaner on the pilot jet. You should have to use the choke to start a cold bike, if you don't need the choke it means that pilot jet is too rich. Go down a size or two and see what happens.
 

jwren00

Member
Oct 30, 2004
36
0
yeah that should fix your problem. Before buying a new pilot jet, try setting hte pilot screw at 2 or 2.5 turns out instead of 1.5. See if that helps your problem. If it does, then go get yourself some leaner pilot jets
 

nikki

Moto Junkie
Apr 21, 2000
5,802
1
Try a BR8ES - it's a hotter plug and your fouling problems will be solved.
 

Jeffack1

Member
Jan 7, 2003
25
0
Thanks for the help.

I am going to do some riding this weekend and will let you know if I can work it out. I think I am going to start by trying the BR8ES plug first (I have a box of these from my jet ski). Then I will work with the air screw and if all else fails, I will order some new jets next week.

Thanks again all.
 

Jeffack1

Member
Jan 7, 2003
25
0
Not so fast. I thought that changing the plug fixed the problem; however, the bike has fouled the plug during warm up the last three times that I rode. This is only happening on the first ride of the day. The bike is running well and I am staying on the pipe while I am riding.

I have tried the air screw at 2 and 2.5 turns out and am still having the problem. Other than this, the bike is setup with the stock jetting.

Does anybody have any other suggestions on what to try? I started with BR9EG plugs and have swithced to a BR8ES. Should I try a BR8EG or is something else going on that I should be looking for?

Thanks,

Jeff
 

elf

Member
Jun 7, 2003
695
0
My 99 and 00 125s ran rich on the bottom, put in a leaner pilot jet and go to the 4 clip on the needle.
Stick with the br8es.
 

Jeffack1

Member
Jan 7, 2003
25
0
I am ordering leaner pilot jets and will go leaner on the needle. I hope this will do it.

Would a bad crank seal be causing this?
 
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