49cc bike wide open on startup

Wavyjay76

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Jun 11, 2019
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20
So i have a 2017 coolster qg50 and i recently just got a problem fixed when ever i would start it the backtire would engage with the engine and if i started it it would go crazy so i recently got the whole situation where when i pull or roll the bike it wont engage my engine anymore and i was so happy and if course another problem happens when i start the bike thank god i had the chain off it revs up so high i thought the bike was going to space lol and there was gas all around the carb and it gave me the nastiest backfire ever sounded like a gun so i restrict a little gas and turn choke off and it idles for 2 seconds and cut off i try to start it again then boom what its been doing full max pinned standing on the gas and it scares the crap out of me not gonna lie scared to start a little 49cc 2stroke now lol i took the carb and its still clean i had cleaned it literally 2 weeks ago and never rode it yet so im soaking the jet and carb bowl and float in seafoam been sitting for abt 1 day and a half gonna take it all out tommrow any tips on what could have caused this by the way i turned my idle screw basically all the way in same resuly still its a single adjustment carb with 1 main jet coolster model qg50
 


Vikingimike01

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Jul 1, 2018
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450
dont turn it in turn it out, screwing it IN will make it idle faster.

also if turning it out doesnt work try looking for an air leak. head, carb flange, cylinder, gaskets..
 

Wavyjay76

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Jun 11, 2019
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dont turn it in turn it out, screwing it IN will make it idle faster.

also if turning it out doesnt work try looking for an air leak. head, carb flange, cylinder, gaskets..
Really i read about screwing it in restricts the gas flow which i felt like its getting way too much gas cause when it starts without me touching the throttle it revs sky high but ill try it out tommrow and see cause if i screw it out pretty sure thats letti g more fuel in and its already revving pinned??
 

Vikingimike01

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No. Thats not how an idle works.

The idle screw is basically a throttle stop. The more you screw it out, the less "throttle" you'll have.
Basically what you are saying is partially right. BUT, it also restricts air. So, you will get less explosive mix, less of a bang, so lower idle. That's the simplest I can explain it.

Not sure if you have ever looked into a carb. Theres a little pin at the end of the throttle screw. It goes in or out if you screw it in or out. And on the carb, the slide. theres like a 45 degree slanted part, that the pin touches. The more the pin is screwed in, the higher the slide will go, and it will raise the pin from the jet, letting in more gas, but since the slide is up more, more air can go into the engine. If you remove your air filter, you can look into it that way, and basically when stopped use your throttle, and you will see that gray-ish slide go up and down. Thats basically what your idle does. Stops the slide at a certain point. The lower the slide is, the lower the idle.
 

Wavyjay76

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Jun 11, 2019
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No. Thats not how an idle works.

The idle screw is basically a throttle stop. The more you screw it out, the less "throttle" you'll have.
Basically what you are saying is partially right. BUT, it also restricts air. So, you will get less explosive mix, less of a bang, so lower idle. That's the simplest I can explain it.

Not sure if you have ever looked into a carb. Theres a little pin at the end of the throttle screw. It goes in or out if you screw it in or out. And on the carb, the slide. theres like a 45 degree slanted part, that the pin touches. The more the pin is screwed in, the higher the slide will go, and it will raise the pin from the jet, letting in more gas, but since the slide is up more, more air can go into the engine. If you remove your air filter, you can look into it that way, and basically when stopped use your throttle, and you will see that gray-ish slide go up and down. Thats basically what your idle does. Stops the slide at a certain point. The lower the slide is, the lower the idle.
Ok thanks how many turns out should i do its not all the way turned in but close to it and i know what slide your talking about thanks for letting me know that i didint know that hopefully once i put my carb back on tommrow and backthe screw out some when i start it. It wont rev max speed by the way with it revving max speed i noticed when i cut it off i hear the clutch spinning down its engaging my centrifugal clutch to is that normal? I know the clutch engages on engine rps and stuff but i wasnt giving it throttle at all the engine was just revving really high the bike is fully auto too so would the clutch engaging the front sprocket on its own due to engine revving max rps without any throttle reasonable for it to do that or it doesnt matter how high the engine gets it should engage unless i give it throttle input if you see what i mean here??
 

Vikingimike01

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Jul 1, 2018
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450
I'm not quite sure what you mean by the clutch, it engages with engine RPM's, not throttle, so it's normal for it to engage with the high idle. Try turning it to about the middle, try starting it up, if it starts revving very high, quickly kill it. It can do damage if you rev it too high. then turn out 2 more turns, start it, see again. Repeat untill engine dies. Try to find the sweetspot of when it won't die, then turn it in half a turn.
 

Wavyjay76

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Jun 11, 2019
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gary55

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Nov 27, 2012
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So like Viking said the screw is a idle adjustment. Not a air fuel adjustment. All the way in is highest idle. All the way out is lowest idle. If the engine is revving to the moon with the choke fully on you have a air leak somewhere. That should be the first thing you find because you won't be able to address clutch or idle issues till you do.
 
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