WOW... things sure have changed

[awfulcanaful]

Hey fellas, I've been riding since I was 4, I'm almost 40...just bought the boy an 07 cr125 for christmas. I let him ride it on th 25th but he only got about 15 mins. b4 it fouled the plug. i own an 88 cr250 bought new it done the same thing fouled plugs rite out of the bow I moved the clip up 1 click and it was fixed.. so when the 125 fouled the second plug I thought it was because the mix from the dealer was rich for break in purpose. I changed the gas and used motul brand ... dealer recommended mixed at 40:1 . yep still fouled the plug.I live in Va. so I'm at sea level w/ hi humidity and temp in the summer. when I rode it it seemed to foul the plug above half throttle,the boy said he thought it was almost at idle....I went to a 420 mainfrom a 430 now it runs good after 1/4 throttle but after 15sec idle if you zap the gas it stumbles loads up ....I've got the a/s out 3 turns I guess I'll go down to the next smaller slow jet....... any help or suggestions are greatly appreciated thanks, Robert

 

[MX86]

125's are high revin bikes. ment to be kept high in revs. drop down to half or below half you will start fouling plugs.. trial and error is all i can recomend

 

[snb73]

Jet it.

 

[FruDaddy]

If it isn't being opened up, you might try a hotter plug until he gets used to the bike. It will reach it's self cleaning temperature sooner thus reducing the carbon build-up. You might also try changing the pilot jet.

 

[rosscopeeko]

maybe try the jd jetting kit for the bike and then buy a lot of plugs and jet it through trial and error.

 

[john stu]

jet it and go back to 32 to 1 when you leaned out the oil (bad move for a reving 125 anyway) you richend the fuel mix.

 

[YZ165]

Wow....

 

[KX250Dad]

When having issues I sugggests going to book settings. The 40:1 I'd question and agree thought be given to 30-32:1. The a/s I suspect is out to far, might consider going to 1.5 - 2 turns. When you use the 40:1 your factory set jetting is off and you'll need adj accordingly. Should the bike idle and bogg on a twist I suspect your back to the air screw...

Good Luck, happy for you and your son both... sounds like your in for a great season.

 

[robwbright]

125's are high revin bikes. ment to be kept high in revs. drop down to half or below half you will start fouling plugs.. trial and error is all i can recomend

Not true. If it's properly jetted, you can bog a 125 around for extended periods and not foul a plug.

 

[robwbright]

Try this:

http://justkdx.dirtrider.net/carbtuning.html

 

[marcusgunby]

If the 07 is like the 05,06(which i think it is)you need to drop at least 3 pilot jet sizes to get it to run correct.You should consider a BR8EV plug instead of the 9 as std as well.

 

[FruDaddy]

jet it and go back to 32 to 1 when you leaned out the oil (bad move for a reving 125 anyway) you richend the fuel mix.

Motul 800 is designed to work at 50:1 (source: http://www.motul.fr/uk/produits/index.html), if you switch to a petroleum based then you should consider 32:1, but for the Motul, 40:1 will be just fine.


To get to the page I referenced, you have to click the racing linke, then click on the motorcycle on the right. Choose 2-stroke on the left and a menu come up allowing you to choose the 800 off road.

 

[Vic]

Marcus!

 

[crashogden]

I have a 06 cr125 and it did the same thing the first time i got it i fixed by running race gas and also make sure u run a fully synthetic oil

 

[YZ250....]

when i got my 07 yz250 it did the same thing. i was mixing at 32 : 1 and now i run 40 : 1 and havnt fouled a plug yet. i went tro like 10 plugs before i figured out the proplem haha.

 

[MX86]

every bike comes Fat from the factory. that way they wont get sued for some shmuck blowing an engine up in leadville colorado

 

[kiwijohn]

Best bet is to read the jetting guide on this forum and do one change at a time to make sure you know what each change does to your engine.

And remember with every gulp of air/fuel/oil your engine takes before it ignites the mixture if there is less oil in your gas - say 40:1 as opposed to 32:1, then each gulp taken by the engine will have less oil, more fuel and the same amount of air. Therefore more gas = a RICHER mixture. It's the opposite of what you think happens.

The reason we have more or less oil is for lubrication. That's why the manufacturers like 32:1 - more oil = safer engine = less break downs... well that's the theory.

One of the oil manufacturers has a good section on tuning/oil/ heat might be Silkolene? I'll check!

Braaaaaaaaap!!

 

[kiwijohn]

My mistake it was Maxima - check this out. Very useful

http://www.maximausa.com/technical/lubenews/springsummer2001.pdf