Engine runs with half choke only

sisdavid

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Mar 31, 2008
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My bike runs on half choke all the time what is wrong, no matter where I move the clip on the pin. Will it be okay if I run half choke all the time?
 

sisdavid

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Mar 31, 2008
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Hold on let me think about this I have the oil mixture kind of high because engine is new, so that maybe what is doing it also I will wait untill I go to 5 oz a gallon and if still does it worry, also, I can't have a air leak I sealed where the carb onto intake with HI temp RTV.
 

Pablo

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Dec 28, 2007
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You have an air leak OR you aren't getting enough fuel.

If you seal the carb/manifold interface and it still only runs 1/2 choke, then some how the jet is not delivering enough full - in that case my first bet is your needle is too fat.
 

thatsdax

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Feb 22, 2008
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I agree. You have an air leak. And if you do not find it, you will burn your engine up fast. You have an air leak somewhere. You better find it. It is easy to find. You only need a can of carb cleaner . While the engine is running, spray a ton of it around where there could be a leak. You know, the common places like, Where the carb clamps on to the motor, Intake manifold, Head Gasket. It is possible the seals at the crank on the sides of the motor could be leaking, like they did on my Honda CR250R. But check the common places first and check it fast or you will burn your engine up in no time. A fresh air leak is certain death for a two stroke. Find it ! and then...Enjoy the ride...
 

Egor

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Jan 30, 2008
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Hold on let me think about this I have the oil mixture kind of high because engine is new, so that maybe what is doing it also I will wait untill I go to 5 oz a gallon and if still does it worry, also, I can't have a air leak I sealed where the carb onto intake with HI temp RTV.
The mix should not make that much difference. I dont like the carb that comes with these things. I would check the float level, make the tabs hold the float just at the seam for the bowl. Check the main jet that it is not plugged with something. I have had to mess with every carb I have gotten, would be nice for one to work with no fuss. I drill a .040 hole in the direction of the air flow from the float area, makes them idle like a Yamaha, there is a post about that. Have fun Dave

PS: Make sure the carb is all the way slid on, the weld gets in the way, if so you will need a file, I use a O ring in carb throat to seat on.
 

misteright1_99

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Mar 21, 2008
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The mix should not make that much difference. I dont like the carb that comes with these things. I would check the float level, make the tabs hold the float just at the seam for the bowl. Check the main jet that it is not plugged with something. I have had to mess with every carb I have gotten, would be nice for one to work with no fuss. I drill a .040 hole in the direction of the air flow from the float area, makes them idle like a Yamaha, there is a post about that. Have fun Dave

PS: Make sure the carb is all the way slid on, the weld gets in the way, if so you will need a file, I use a O ring in carb throat to seat on.
I saw that post on drilling the .040 hole in the carb and did it and mannnnn it made sooo much difference. I too have the carb/intake oringed, no rtv. I guess it is possible that if there is way too much oil to fuel then it might need less air to run, but I would still look for an air leak.
 

Egor

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I saw that post on drilling the .040 hole in the carb and did it and mannnnn it made sooo much difference. I too have the carb/intake oringed, no rtv. I guess it is possible that if there is way too much oil to fuel then it might need less air to run, but I would still look for an air leak.
I'm glad someone got a chance to try the carb mod. Good to hear yours works as well as mine. My last build is running so well with it I am not looking for a real carb off a motorcycle anymore. It will pull down slow and then just keep going. Have fun, Dave
 

spad4me

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Jan 20, 2008
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Did you spray carb cleaner or wd 40 around the carb while the engine is running , and listen for a sputter.


You could have a clogged jet or a clogged needle and seat.
 

sisdavid

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Mar 31, 2008
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Pablo was right. When I put the engine together I noticed that the needle in the carb was kind of fat after pablo mentioned it, so I switched the pin out with one I know runs good. Runs perfect. Sanded the pin that was in it for awhile, put it back in runs much better now only 1/4 choke. Intentionally did not sand down too much because I can not go back. Will sand some more today, and see what happends. Thanks for all of the help, Especially Pablo, and ThatsDax. Pablo because he called it and ThatsDax for scareing me into fixing it right, and for haveing a good pin in the engine that I bought from him to begin with. The good pin cam out of the Dax engine. It was a BoyGoFast engine that had the pin problem. Not trying to say it is a crummy engine just something to look out for with the Boy Go Fast engine. It is a slant spark 50cc.
 

Pablo

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I learned that one the hard way - I went through weeks of battling the same problem, so I bought a new carb ($22) and it ran like a champ! I sent the old carb to Norman. He's the one to thank - he said "Your needle has no taper!" (actually it had some, but it was too fat)

Anyhow I think there obviously is some flaw in China......


Cool thing is I now have two carbs to experiment with.
 

MarkTur

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May 23, 2008
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I saw that post on drilling the .040 hole in the carb and did it and mannnnn it made sooo much difference. I too have the carb/intake oringed, no rtv. I guess it is possible that if there is way too much oil to fuel then it might need less air to run, but I would still look for an air leak.
Please point me to the post...and how hard was it to do, and what's the benefit?

Have you cleaned up your ports and gaskets yet? I think I'm going to do a bunch of work on the carb this week after what I'm reading...

Thanks,
Mark
 

misteright1_99

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Mar 21, 2008
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Please point me to the post...and how hard was it to do, and what's the benefit?

Have you cleaned up your ports and gaskets yet? I think I'm going to do a bunch of work on the carb this week after what I'm reading...

Thanks,
Mark

I have cleaned all my ports and matched them to the intake and exhaust, installed all new gaskets. Made for a much smoother running engine. I am now in the process of rejetting. I will have to look for the post drilling the carb. It is simple to do, just need to go to a hobby shop and fing the right sized drill bit, and collett for dremel. It does make a difference with the idle since these carbs have no idle circuit..
 

sisdavid

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Mar 31, 2008
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Porting, Make sure you stick some rag or something in the exaust pipe when grinding on it. So you do not get metal flakes back in your engine.
 

Graham

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Jan 19, 2009
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boston, ma
Say your bike needs the choke to be at least 1/3 the way down to start. But once it does you can pull the choke back up and it runs fine. Is this a problem?