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Popping on decel and won't idle right

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Bike won't idle right and is popping on the decel loud. Bike has new motor piston head and sleeve. I put a Jd jetting kit 45 pilot 170 main blue needle on 3rd clip. One thing I noticed is the o ring for air screw seems a little big would this cause these problems. Any help would awesome thanks.

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Loose air boot? Air leak? Use a new header gasket? Or the plate that goes sandwiched agains the slide has a rubber seal that goes bad and needs replacing as well. Jetting sounds reasonable and fuel screw, how many out?

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Has new header gasket. Bike ran good before rebuild. Carb did sit for 5 months. I did replace the rubber seal on slide plate 4 years ago. Fuel screw 2 turn out.

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Bike won't idle right and is popping on the decel loud. Bike has new motor piston head and sleeve. I put a Jd jetting kit 45 pilot 170 main blue needle on 3rd clip. One thing I noticed is the o ring for air screw seems a little big would this cause these problems. Any help would awesome thanks.

 

ok, so you have a lean condition, with the throttle closed.

 

- leaking fuel screw

- hot start not dropped in cavity all the way, now leaking

- loose carb boots

- passage above pilot jet is not perfectly cleared out (use fishing line)'

- pilot jet is partially corroded (replace it)

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Ok thanks krannie . The pilot jet is new but will check the passage above. Going to replace oil ring on fuel screw. Is there a way I can check hot start plunger?

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Ok thanks krannie . The pilot jet is new but will check the passage above. Going to replace oil ring on fuel screw. Is there a way I can check hot start plunger?

 

The plastic nut that holds the hot start plunger cable can crack, and then the spring tension on the hot start plunger is compromised, causing it to leak......or, water has gotten inside the pluger cavity (common) and corroded the plunger up just enough for it to leak.

 

The YZ has the hot start on the top of the carb, which is hard to get to, but it can be done by only removing the tank, and loosening the carb so it will rotate a bit.

 

I think it's a 12mm open-end wrench that will fit down in there..... but a ground down one works really well....if you have an extra one to grind down...

Once you get it loose you can kind of get to it with your fingers....

 

You are best to replace the plastic nut with an aluminum one (ebay, zip ty, etc)

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Ok thanks I already replaced the plastic hot start nut with a zip ty one a couple years ago do I will check the plunger and go from there thanks for the help . Probably going to be a clogged pilot passage or leaking fuel screw. I hope will let you guys know how it goes thanks again.

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Got the bike dialed in finally. Had a broken oil ring on the fuel screw and a I hate to say this but I put the slide plate in upside down. I felt like A dumb ass. But I got it all figured out. Thanks for the help.

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Ok so I took the bike out yesterday and the bike runs amazing. But it's still a little stubborn to start hot or cold and some times the idle will not back down. I tried adjusting the fuel screw and the idle and it kept changing. One time I even turned the fuel screw in all the way and the bike didn't die. Stumped.....

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You say the motor has 0 hours, but what about the carb?

 

Needle jets wear out

 

Did you adjust the fuel screw on a hot motor, lowest possible idle with idle screw, starting at 1 turn out on the fuel screw?

 

...and you ended up with how many turns out on the fuel screw to reach highest idle ?

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The carb has been rebuilt. With a Jd jetting kit new .170 main 45 pilot blue needle on 3rd clip down all brand new new diaphragm and all new seals and oil rings all other jets are stock and 8 years old.

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The carb has been rebuilt. With a Jd jetting kit new .170 main 45 pilot blue needle on 3rd clip down all brand new new diaphragm and all new seals and oil rings all other jets are stock and 8 years old.

 

Your needle jet (not the jet needle) is a wear component, and needs to be replaced after a 100+ hours.

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Ok I will try that I have had the bike sense 2006 and never changed that thanks. krannie

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Ok put the needle jet in last night and bike fired right up. And once it was warm first kick three in a row. Thanks for the help krannie .

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