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Discussion Starter #1
I've finally bought the kids their dirt bikes. I had to get one for me as well because obviously, and also if they're riding trails it's probably best the don't do it alone.

So I bought an 03 ttr 125 to pass onto the oldest when the youngest is ready to start riding. It wouldn't idle so I got a good price.

Cleaned up the carb and replaced the destroyed diaphragm on the idle circuit and now it idles well. Unfortunately now when I twist the throttle, the revs take quite some time to go back down. When I was tuning the carb using the idle screw, it still responds fairly quickly. If it's about to die via screw adjustment, though, then I give it some throttle and it doesn't drop to almost dying again.

Anywho, I don't know what causes this and where to start with the surging. It only does it with throttle, not on its own. Let me know your fixes.
Thanks fellas.
 

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Discussion Starter #3
i did a whole lot of tuning with the mixture and idle screw to get it idling nicely. i don't know if any of it was right though. I was going to reset the mixture screw to 2 turns out. what is the default for the idle screw? i want to try tuning them again. i'm also going to check to make sure the needle slides smoothly and the throttle cable isn't getting hung up on anything.
 

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Discussion Starter #5
yeah, i've got the mixture screw, it's the idle screw i'm curious about. they also don't give a float measurement that i can find.
 

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Discussion Starter #7
yeah it is, that's a fun way to measure float level.

still no standard position for idle screw.
 

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If the revs are sticking then somthing isn't right either mixture is wrong or air is getting in somehow.

I would set the carb up to the stock setting presuming it not been jetted etc once you have the mixture screw, and float level back to stock then ajust the idle to a nice level (for now) and then look for leaks or poor fitment, I use brake cleaner but some like to use wd40 etc.

If you find any leaks rectify them and then ajust idle accordingly.

I wouldnt be deviating from stock setting till you can get it iderling and reving right while not underload.

I would also look at the basics while I was there, fresh fuel,plugs etc although that tends to cause a bog not stick..

Good luck
 

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Discussion Starter #9
it's fine while idling. it doesn't surge at all. i already tested for leaks and there aren't any. as i said, i can't find a stock setting for the idle screw. i started with the mixture screw at the stock position. when i was cleaning the carb i checked the jet sizes and they're at stock, i also changed the plug as well. Idle is great, it just takes a while to come down once the throttle is twisted.
 
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