Air/Fuel Setting Mystery...I need help!

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Criswald

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I recently purchased a King Motor Baja KSRC-002 with a 30.5cc engine and have been fighting an air/fuel problem after 2 tanks of fuel. I went to start the engine one afternoon and could not get it to stay running without holding the throttle open. I went to the internet and read several different forums that instructed me to open the LOW side needle 1 1/2 turns from closed and the HI side needle 1 1/3 turns from closed. Making small adjustments (1/16 turns) to the LOW side while trying to start the engine I found that I could not get the engine to idle unless the LOW side jet is completely closed. (Hmmm!) As soon as I crack the jet open just a small amount (once again 1/16) the engine stalls. With the LOW side jet closed I sprayed WD-40 around the intake manifold area to check for un-metered air getting into the engine. (No changes in the idle were detected) I replaced the spark plug. I removed the carburetor, disassembled it and thoroughly cleaned it with carb cleaner and shop air. Once carb was cleaned and reinstalled on the engine I was still having the same problem. I have inspected the plug and it has good color.(light charcoal gray...not black and not white) All in all the car runs great and idles as long as I keep the LOW jet completely closed but I am worried that running it like this will cause a more serious problem. If anyone has experienced this problem please let me know what to do. Thanks
 
Correction!

Criswald said:
I recently purchased a King Motor Baja KSRC-002 with a 30.5cc engine and have been fighting an air/fuel problem after 2 tanks of fuel. I went to start the engine one afternoon and could not get it to stay running without holding the throttle open. I went to the internet and read several different forums that instructed me to open the LOW side needle 1 1/2 turns from closed and the HI side needle 1 1/3 turns from closed. Making small adjustments (1/16 turns) to the LOW side while trying to start the engine I found that I could not get the engine to idle unless the LOW side jet is completely closed. (Hmmm!) As soon as I crack the jet open just a small amount (once again 1/16) the engine stalls. With the LOW side jet closed I sprayed WD-40 around the intake manifold area to check for un-metered air getting into the engine. (No changes in the idle were detected) I replaced the spark plug. I removed the carburetor, disassembled it and thoroughly cleaned it with carb cleaner and shop air. Once carb was cleaned and reinstalled on the engine I was still having the same problem. I have inspected the plug and it has good color.(light charcoal gray...not black and not white) All in all the car runs great and idles as long as I keep the LOW jet completely closed but I am worried that running it like this will cause a more serious problem. If anyone has experienced this problem please let me know what to do. Thanks
Click to expand...

Correction...I set the HI side jet to 1 1/4 turns out from closed to start the tuning process.
 
Low needle should be 1 1/4 from fully in High needle 1 1/2 from fully in, if this don't fix it check that the fuel tank vent is not block also check fuel lines for cracks and carbie for leaks
 
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You have a bad gasket in the carb( an air leak). You need to rebuild it. If the problem is still ther then you need to set the carb back to factory settings.:D
 
its your carb, i went thru the same ordeal with a brand new k,m carb there junk i replaced gaskets changed fuel lines i,d ruled out the carb with it being new but then there was nothing else it could be, i got a new wallbro 603 fitted it and that was it weeks of pissing about cured in 10 minutes.
 
have you adjusted the idle screw? this is the one below the H/L screws big one with a spring,if you have not then i suggest you do before buying anything,thats what it's for to set your idle
reset to factory settings, and adjust the idle screw while it's running, place the baja on a box if you have to,keep it from driving away ,then adjust the H/L screws after you got it idling, you may have to come back to it to lower or raise the idle,
 
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Is there any way to take a look at the carb while on the engine when adjusting the idle screw to see how much the gap is open, kinda like looking at a nitro carb when adjusting the idle which sound be a few mm's. Just wondering if it's possible to do a same check on a walbro carb and how much the opening should be at idle or do ya just adjust it bit by bit when ya got the l&h needles at factory settings until the engine starts
 
well its a bit difficult to look down the carbs throat unless you remove the air filter,but again if you don't have it's wheels off the ground and your looking down the carb you could get nailed by it in the face, if it takes off while your doing something like that,
i suggest adjusting bit by bit till it stays running, once you get that done then start to mess with the low and high end adjustments.
 
Ok, was just curious. I was thinking of taking a look with the carb off if it would be easier to see that way just to get an idea of a starting point gap but guess its just easier to adjust the idle til it starts up
 
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