Dirt Bike Repair & Maintenance Forum

I bought my son (12) a new YZ85.  He's been having problems fouling plugs.  Its getting pretty bad(and expensive), as somedays he'll go through a plug in about 30 minutes.  He isn't good enough on it yet to really be riding hard, so I'm sure that's most of the problem. However, until that takes care of itself..... does anyone have any tips?

I'm running the Yamaha oil 2R at the manual recommended 30:1 with pump premium unleaded, and the stock BR10EG plug

I can hear it loading up when he is out riding it, and when he does get on it, you can hear it clear up and begin to run better, however, most of the time its in the 1/4 to 1/2 throttle max.

Hotter plug?
Different oil? (plugs are black and wet when I change it out and put in another new $7 plug  

I hate to start screwing with the carb jetting, unless I have to.

Does anyone know if Yamaha ships these with a 1 size bigger jet for break-in and maybe it needs to be re-jetted? (I thought this practice was stopped years ago?)

Thanks in advace  

Go to 32:1 first off. Your to rich. And they come with 2 jet needles . Most cases i would say dont lean out. But would here at to 32. And i know dave recomends a hotter plug.
Skip has one to. And he could tell you better for your altitude and carb setting.  
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It's called wash your bike stupid.

PS. Yes, the bike is set up right. Just wants to be run hot and on the pipe.  
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It's called wash your bike stupid.

hold on yore running a br10eg

yamaha made a mistake on this bike saying it was a br10eg but thats not the right plug for it

the real plug you should use is the br10eg

you wont foul a plug for a while now

this exact thing happened to me to let you know  
DRFMAS

yes, a BR10EG.
I think you typo'd on your reply.
You said to run a BR10EG instead of BR10EG?

What did you mean? Should I go a little hotter(like a BR9EG or BR8EG?)  

Yeah, Dave changed his out too. DAVE??????????  
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It's called wash your bike stupid.

Along this same topic, another question for you guys on the YZ85?

Are these Keihin carbs on the low speed circuit..... is an AIR screw,  or is it a FUEL screw  

The one with the spring is the idle screw. (Throttle stop) The other is the pilot air screw.  
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It's called wash your bike stupid.

PS. You need to read the manual cover to cover. Will tell you all this.  
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It's called wash your bike stupid.

def. use the BR9EG. you said your son wasnt riding it hard yet .. well i might try a BR8EG. ive never used one but ive heard they work well for beginners. in my yz85.. (sold it  ... i used to run a br9eg for every riding i did... i dont know if im right, but im 90% sure  

I'll chime in

BR9EG is the correct plug - Yamaha spec'd the incorrect plug when they listed the BR10EG for this bike.  The BR9EG clears up most of the fouling problems.

30:1 Yamalube 2R is a fine premix ratio for this bike.

The screw on the side, like Woods said, is the airscrew.  Stock it would be around 2 turns out.

These bikes shipped with only one jet needle (unlike other Yamaha's)  the bike's factory jetting is 45 pilot, NBKF needle on the 2nd clip form the top, and 138 main.  This bike tends to run a little rich off the bottom, so I'd recommend running a 42 pilot instead.  When it's really hot out (over 90) you can run the 135 main jet.  

Screwwing with carbs is fact of life with these bikes - you will have to do some tweaking no matter what.  
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Here we go again!

Thanks Skip.  
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It's called wash your bike stupid.

Yes, even on the modified motors they run a BR9EG.  The BR10EG is just too cold a plug.

All we did on my son's is run the BR9EG, and I turned the air screw out another half turn.  We also ran 32:1 Yamalube 2R.

Bike held up great for 2 years.  
Dave H 2006 YZ250
(2008 YZ 125 son)

Thx guys, will give the 9 plug a shot  

Well, i put the 9 plug in (br9eg)  and it fouled in about 40 minutes.  I had bought another BR9ES (non racing plug, bigger electrode),  based on the dealer thinking the bigger electrode would not foul as fast.
IT was a good idea, but it too fouled in about 40 minutes.
So... I am stuck here I think with taking the carb apart on this thing and rejetting it (against my dealers recommendation).   Anyone have any other thoughts on how I can make this thing ridable for my son?