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2002 YZ125 2-stroke Idling Issue/Starting Issue

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I purchased a 2002 YZ125 2 weeks ago. It has PHAT head upgrade, aftermarket Reed. PO said he didnt ride much and bike sat for 6 months. On the day of purchase it fired with 1 kick.

 

Last week, i took it to Carnegie. Just drained gas out of carb & tank and filled in new gas. 91 octane + Klotz R50 premix in a 32:1 mixture (I was told this was the best oil, open to hear other suggestions). The bike ran fine for 2 hours and then on an uphill it stopped. I couldnt fire it up neither bump start. In bump start it would do "brrrr brrrr" {pardon my lack of expression} but wouldnt start. 

 

I noticed petcock was leaking gas so as float bowl. I will order the O-Rings for the petcock and the bowl gasket. On examining the plug, it was fouled. Dipped it in kerosene, but i will order a new plug. 

 

Examining the jets, they were not clogged bad, neither there was dirt inside. The air filter was Ok. Carb disassembled and soaked in pinesol/water now. Air Filter washed and cleaned. Curious, what other reason could lead to this symptom?

 

Ohh - There was quite a bit of white smoke during riding (I think i was riding over 3/4 throttle) and quite a bit of black spooge oozing out from exhaust. Plan to repack the exhaust.

 

Questions I have :

1. Any way to identify the current jet sizes? There is no numbers/letters scribed on them.

 

2. Since i am wanting to change the O-Rings & the fact that the jets are unnumbered, is it better to just order a carb rebuild kit with jets? If so, i see many of them on ebay but i dont know which one is better. Any brand recommended?

 

3. Do i need to replace the throttle valve/slide? {Based on the picture showing the nicks on the ends}

 

4. If i understand correctly, the "Throttle Stop Screw" is same as "Idle Screw" ? It was turned all the way in (with the nut  flush on top). Could that have potentially caused the nicks as described in #3 ? Actually, post warmup, bike wasnt idling fine. It would stop after a file. If this screw was turned all the way in, i would need to go up pilot i assume.

 

Picture of throttle valve :: 

 

IMG_1813.JPG

Edited by abhijitz

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How well did you mix the oil and gas ? You should fill container of known volume halfway with fuel then oil enough for when it's full shake the crap out of it for 30-60 seconds then fill the rest of the way . This ensures you get a good even mix otherwise , oil sinks

Or you left the choke on possibly..... Lol.

Being that you rode for a while both of these aren't too likely . How is the compression , even on a 125 you should be able to easily feel the compression strokes . If you can kick through or use your hand without feeling the blips of force to turn the kicker it's a good chance the bike needs a rebuild

Edited by Swes

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How well did you mix the oil and gas ? You should fill container of known volume halfway with fuel then oil enough for when it's full shake the crap out of it for 30-60 seconds then fill the rest of the way . This ensures you get a good even mix otherwise , oil sinks

Or you left the choke on possibly..... Lol.

Being that you rode for a while both of these aren't too likely . How is the compression , even on a 125 you should be able to easily feel the compression strokes . If you can kick through or use your hand without feeling the blips of force to turn the kicker it's a good chance the bike needs a rebuild

 

Acknowledged. Thats how i do. In a 2 gal gas can, pour 1 gal gas, pour premix, shake with a dance (good workout) wait couple of seconds, our 1/2 gal shake again and pour the remainign 1/2 gal and shake. 

 

Choke wasnt ON.

 

Compression feels good. I havent measured that yet .. will do tonight. 

Edited by abhijitz

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Could be your tank had some dirt in it and proceeds to clog up the needle valve flooding the bike.

Fix by holding the kill switch and having the fuel off and kick around a few times this will blow out the extra fuel.

Put a filter between tank and carb or clean the tank or both.

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