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Yz125 stuttering at half throttle

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Hey guys im looking for an opinion. I have an 01 yz125 and its sputtering half throttle right before powerband. I have checked every last thing from jetting to stator ohms to reeds, gas cap etc ive pretty much narrowed it down to possibly the cdi going bad. Now im just curious on what symptoms would designate a bad cdi? Any help is greatly appreciated 

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Not knowing how you tested your jetting I won't comment,  but I am betting it isn't your CDI. 

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I apologize i may have worded it wrong but the carb is spotless and its the stock jetting that it has been for the few years ive had it with no issue

Edited by 01buck1/4

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1 hour ago, ossagp said:

Not knowing how you tested your jetting I won't comment,  but I am betting it isn't your CDI. 

My jetting has been stock for the past couple years ive owned it and it never had this problem ever. And i made sure the carb the jets and every orfice are clear and clean 

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as in the jet where the throttle needle slides into? And if it is worn what would be a physical sign? Thankyou too!

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23 minutes ago, 01buck1/4 said:

as in the jet where the throttle needle slides into? And if it is worn what would be a physical sign? Thankyou too!

They last about 200 hours. They oval out. You can't see it with the naked eye. Also called an emulsion tube. Not replaceable on all carbs....but it is designed to wear out and be replaced.

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If yours has the Mikuni that came on it,  the needle jet and needle are removable and replaceable.  If you are buying anything before setting the float carefully and using the procedure that the factory manual suggests you could vary well be wasting your time and money.  The float needles and seats wear as well.   Viton tipped needles  don't wear like the ones they replace,  but the springs in the needles still go soft.  

A keihin pwk carburetor works well on my yz125's and in the end may look like a plausible upgrade for yours.   However,  if yours was mine I would see that the float is set right (those move more often than most realize) before I did anything else,  particularly since you mention that this is a newly developed condition. 

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1 hour ago, ossagp said:

If yours has the Mikuni that came on it,  the needle jet and needle are removable and replaceable.  If you are buying anything before setting the float carefully and using the procedure that the factory manual suggests you could vary well be wasting your time and money.  The float needles and seats wear as well.   Viton tipped needles  don't wear like the ones they replace,  but the springs in the needles still go soft.  

A keihin pwk carburetor works well on my yz125's and in the end may look like a plausible upgrade for yours.   However,  if yours was mine I would see that the float is set right (those move more often than most realize) before I did anything else,  particularly since you mention that this is a newly developed condition. 

By spring in the needle going soft what do you mean? I think im onto something now

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1 hour ago, ossagp said:

If yours has the Mikuni that came on it,  the needle jet and needle are removable and replaceable.  If you are buying anything before setting the float carefully and using the procedure that the factory manual suggests you could vary well be wasting your time and money.  The float needles and seats wear as well.   Viton tipped needles  don't wear like the ones they replace,  but the springs in the needles still go soft.  

A keihin pwk carburetor works well on my yz125's and in the end may look like a plausible upgrade for yours.   However,  if yours was mine I would see that the float is set right (those move more often than most realize) before I did anything else,  particularly since you mention that this is a newly developed condition. 

As in the spring loaded  pin the float tang comes in contact with? Reason asking is when i flipped the carb upside down that spring compresses under the weight of the float.

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That is the spring I was talking about.  The way yamaha instructs you to set the float will allow for a certain amount of compensation for a spring that though softer than what new is,  still has some life.  Setting it is the first thing necessary to establish the base for jetting anyway you go (or at least knowing what it is so that you can return to that point).   The bikes you used to see running carburetors and winning races on tv all had the float set at least before each event. 

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