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Old 09-20-2017, 05:50 AM
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Default Tuning problems yz125 2001

     

Hi, have a yz125 2001

At first I was having very bad hanging idle & not idling at all.
I have changed the reed petals and this seems to have fixed that.

Moving on to the tuning. I have set the air screw to default (1 - 1/2) and started from there, My understanding is that you get the highest idle from here (the sweet spot) and then tune the idle screw however when I do this my idle screw doesn't really have any effect even fully out so it's idling too high. Can someone please tell me why this is?

I have manged to get a good idle by altering the air screw + idle screw until it does however it isn't at the "sweet spot", I have no idea if the bike rides fine yet as I haven't had the chance to go out

Shouldn't the engine stall if the slide is fully down with the idle screw been fully out?


(all the carb is clean, jets are clean etc)
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Old 09-20-2017, 10:31 AM
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Have you checked for leaks? It sounds like air may be getting into the motor through somewhere else that is not the carb.
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Old 09-21-2017, 01:04 PM
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I have checked the crank seal and ive sprayed carb cleaner all round the boot etc nothing happens.

for the bike to idle the air screw has to be half a turn out but obviously the bike doesn't have good throttle response

How come the idle screw isn't doing anything when the air screw is 1 - 1/2 turns out?

I have checked the jets, pilot jet is correct however the main jet is 420 when it should be #450 do you think this could cause it?

---------- Post added at 12:04 PM ---------- Previous post was at 10:10 AM ----------

Do you think I need a richer pilot jet?
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Old 09-21-2017, 01:43 PM
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to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet. If your engine doesn’t respond to air screw changes, then you either have a dirty carb, or the pilot jet is way too rich. When the pilot jet is way too rich, you are forced to use the idle screw to open the slide so far in order to keep the engine running that the pilot circuit is partially bypassed, and the engine is actually starting to draw fuel through the needle jet.
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Old 09-22-2017, 04:38 AM
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Quote:
Originally Posted by MPCORE856 View Post
to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet. If your engine doesn’t respond to air screw changes, then you either have a dirty carb, or the pilot jet is way too rich. When the pilot jet is way too rich, you are forced to use the idle screw to open the slide so far in order to keep the engine running that the pilot circuit is partially bypassed, and the engine is actually starting to draw fuel through the needle jet.

Do you mean if you are getting the highest idle under 1 turn you need a bigger jet? because mine it set at half a turn just so I can get a steady idle
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Old 09-22-2017, 11:34 AM
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What number is your idle jet?

Also check your choke circuit & knob that is in good condition, closes properly and does not leak.
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Old 09-22-2017, 12:04 PM
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so like I said if your screw from closed is anything less than 1 turn from closed then you need a larger pilot jet, if its more than 2.5 turns then you need a smaller pilot jet so try and start with the 1 turn, if you cant get 1 turn go smaller on that pilot. if anyone else has an input or if im missing something let me know, also remember the altitude and weather (hot, cold) also determine the jetting you should be at. there's no way I can tell you how to jet your bike properly only because im jetted for a different climate than you are most likely, in Arizona we have a dry hot hot heat and low altitude, unless someone who rides with you in the same area same climate same weather (hot, cold) and same altitude then they would be able to help with you jet. sorry if im no help
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Old 09-22-2017, 02:24 PM
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Take out your pilot and clean it. Hold it up to the light or use a flashlight. Spray carb cleaner (lookout eyes) then poke a wire through, I use a guitar string. Don't try to shove something through that doesn't fit like a needle or pin that will be too big. A strand of wire appx .10mm. Then hit with compressed air, carb cleaner, compressed air. Then look again. That little tiny light shod be nice and round and perfect. If it still is giving you trouble after that you should pull the cArb off and clean all.



also.. mcore weren't you in the other thread asking someone to explain jetting? Here, you are giving advice as if you have a clear understanding. You jerking my chain? I don't like to waste my time trying to help someone who doesn't want or actually need help.
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