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What should I do now?

Joined
Feb 4, 2007
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#1
My bike is a '97 YZ 125. This is my first bike and I'm slowly learning everything about it. I am having a problem where my bike will run great, then the next time I go to start it up (1-2 days later), it either won't start, or it starts and won't stay at idle then eventually foul the plug. I am running a BR7ES plug and 32:1 using Yamalube. I am doing only trail and pit riding, so I am not really going "balls to the wall" all the time. I don't know how to jet (yet) and I'm debating whether I should attempt it myself or just bring it in... Help!
 
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Apr 8, 2007
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#2
learn how to jet now so that you will know how. Plus youll be saving yourself alot of money
 
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#5
You say it wont idle and then fouls the plug. Well, if you go out and run it hard for a bit does it clear out or does it still foul the plug? A 7 is a little hot for a 125. Jetting could be an issue. The riding style you described could also cause some problems. A YZ 125 isn't exactly a pit bike. How long do you let it idle for?
 
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#6
check your jetting and run 40:1, if your just running trails u don't need 32:1, even though I know many people will disagree w/ me, it will not foul as easy and will save you some oil too. :cool: oh and I would jet it to run the 8, like every one else said the 7 is alittle hot
 
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#7
for a 125, 7 is an extreme. Honda recommends to use probably a 9, People use 8's and even in somecases it is too hot of a plug.
 
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Jul 1, 2006
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#8
You're putting a 2 stroke. They don't much like that. Try re-jetting a little leaner with the 8 or stock style 9 series S NGK plug as stated above. While balls to the wall isn't necessary putting a smoker usually leads to fouling unless lean on the idle, pilot and rod. Try some agressive runs to clean out the case. Make sure to repack the silencer often as it will load with oil. 40:1 or even 50:1 will be fine if you don't race or ride it hard always. I used to race/practice with 50:1 and my 125s eventually ate big ends. But for trail speeds you're okay. Make sure you settle on a ratio and jet for it. Do not adjust jetting with the oil ratio to correct jetting/spooge issues. It just takes a sensitive hand and lots of trial and error.
 

Uchytil

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Jun 29, 2003
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#9
Ryan, You have a good bike there! I'm trying to sell one right now that my son got in 97. Funny, he bought it in Maine near Portland. Anyway, over the years of racing I was his mechanic and, other than top ends and a few entire rebuilds, we always ran the stock spark plug at a oil ratio of 20:1 (recommended by Yamaha) with very little, if any, spooge. We usually changed a plug once a season or so. Jetting is the key to staying on top of a crisp running engine. In order for jetting to work you must have a tight engine to start with. If the engine is worn, i.e. leaky gaskets & seals, worn top end, cracked reeds, dirty carb circuits, dirty air filter, dirty power valve, clogged silencer, etc, then no jetting will help, maybe only mask symptoms temporarily. While you will get alot of advise you would do well to get a service manual and read it. The Eric Gorr book covers basic, and up, tips on maintaining and repairing these type of bikes. If you have a tight, fresh, engine you can be assured that jetting will be your biggest and best friend to running right. One other note, that bike is made to run not idle around. As you get better so will the bike. Maybe there's a DNR'r near you that can assist you somehow. Sometimes seeing things done helps. I think there may be a local chapter that covers the Northeast in here. Also, you'd have alot of fun if you hit some of the local tracks. There's a nice one near Skowhegan but I guess that depends on where you hail from. Good luck.
 

Uchytil

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#10
Uchytil said:
oil ratio of 20:1 (recommended by Yamaha)
Actually I think it was 30:1. Sorry, my feeble mind and being 7000 miles from home, and this damn sandstorm is filling up my keyboard, lol!

I'm sure the rest is right. I'm glad I'm finally outa here next week. This one year tanning session is getting old.....