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HELP my BRAND NEW 2017 yz 125 wont idle

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I just bought a brand new yz 125 and when i got it home the thing wouldnt idle so i held the gas for 15 minutes and did the heat cycles and it still wouldnt idle so i turned the idle speed screw in and now it climbs idle, itll go from revving or idling realllyy slow like its about to die to idling high when it is revved... It also feels like it has no torque at all when i hit powerband on it after heat cycles it wouldnt pull the front wheel up in 2 or 3rd without popping the clutch... Anybody have any suggestions?

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Okay, relax and things will be alright. First thing, make sure that your throttle cable has the correct free play in it. Check all carb fittings and make sure they are tight, clean and oil the air filter because the factory never does a good job with that.

Now, warm up the bike for 3-4 minutes and then adjust your pilot screw by holding a slightly high idle at the throttle (you might need a friend to help) and turn the pilot screw (the little tiny one at a slight angle towards the back of the left side of your carb) until it reaches the HIGHEST possible idle, then let go of the throttle and adjust the idle screw (the biggest screw on the left side of your carb) until you have an acceptable idle.

If none of that works, go ride your bike and break it in, then try those adjustments again. BTW, a 125 will be a fun ride but NEVER have torque.

Post your results

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Are you still running what was in it from the dealer?

Idle screw or air screw sometimes confused if it's your first.

Photos are easy to load, lets see what you got.

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Not enough info to go off of, could be a lot of things.  A video would go a long way in helping the folks here diagnose what's going on.  If you turn the idle up and then it hangs on the way down (not wanting to fall all the way back down to a low idle, or taking a long time to do so), it sounds like lean jetting (air screw or pilot jet) or an air leak.  But with the bike being brand new, those seem pretty unlikely.

Though personally, I adjust my 2 strokes to not idle, and I wouldn't be surprised if it came from the dealership like that on purpose.  My last brand new bike (16 YZ250) came from the dealer with no idle.

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quoted: when i got it home the thing wouldnt idle so i held the gas for 15 minutes and did the heat cycles and it still wouldnt idle

 

Are you saying you did heat cycles / break-in at home idling/revving the engine in neutral ?

 

If so, the break-in won't be done right (piston ring glazed, blowby) and the bottom end full of excess premix (won't idle nor hit powerband cleanly).

Edited by mlatour

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Thank you NYMXer i did your proccess and returned it to factory settings and it climbs idle a little still but not enough to notice and doesnt effect the performance so im just going to leave it

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12 hours ago, mlatour said:

quoted: when i got it home the thing wouldnt idle so i held the gas for 15 minutes and did the heat cycles and it still wouldnt idle

 

Are you saying you did heat cycles / break-in at home idling/revving the engine in neutral ?

 

If so, the break-in won't be done right (piston ring glazed, blowby) and the bottom end full of excess premix (won't idle nor hit powerband cleanly).

15 minutes sitting still with no airflow on any bike is plumb scary, especially on a brand new one. 30 lashes,,,,no, make it 50!

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