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Discussion Starter #1
Looking for some help with my’73 cheetah 340. Having carburetor issues. It’s a mikuni vm44. It keeps flooding the engine. I’ve pulled it apart, cleaned and reassembled. Needle has the c-clip on the upper most groove in the piston. The fuel screw set at 2 turns out. Air idle screw two turns out. Still floods. Float is set and works stopping fuel when the bowl is full. Choke plunger has been set. Seems no matter what is done, the engine keeps flooding. I had it start up yesterday for the first time after I cleaned the carb. It ran for maybe a minute. Then the idle started to slowly rise without touching anything. I went to adjust the idle screw but turning it in or out made no difference the idle kept rising. I shut the engine off because the idle kept rising to much. Then it would not fire when trying to start it again. Couple pulls with no choke and plugs are soaked.
Did the 340 come with a vm44 or did someone put this carb on? Should I be looking for a different carb to use or can the jets/needles be changed to work with this engine?
 

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It would have come with a Walbro carb. If anything, a VM32 would have been lots for the 340. Find another carb
 

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Discussion Starter #3
It would have come with a Walbro carb. If anything, a VM32 would have been lots for the 340. Find another carb
thank you! I thought the vm44 was too big. From google searches the largest I seen on a 340 was a vm38.
there’s a guy selling a vm26 close by. Would that work or too small?
 

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Early to mid nineties models like a Cheetah and Bearcat with a 340 use a VM32. A VM26 would be too small
 

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Discussion Starter #5
Ok. I think I might have a walbro carb in a box of parts I bought. Are the walbro all the same or is there a number I should look for on it? Thanks for your help!
 

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Sorry, I know nothing about a Walbro other than a long long time ago I took one off my Scorpion Whip and replaced it with a Mikuni cause it was crap.
 

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It very well could be your center seal on the 340. Is there gas in the pulse line? I run a single 38mm on my 440 with no issues, but there is an issue if the center seals goes.
 

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Discussion Starter #9
It very well could be your center seal on the 340. Is there gas in the pulse line? I run a single 38mm on my 440 with no issues, but there is an issue if the center seals goes.
The fuel pump was leaking through but since I replaced the pump with a new unit, there hasn’t been fuel in the pulse line.
 

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If both cylinders are within 10% of 110 psi, that should be good. With no gas in the pulse line, the center seal could be ok, but not necessarily. If you had the idle slowly rise and nothing you did made a difference, I would say you have an air leak. Could be the intake leak or a PTO or MAG seal leak.
 

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That of course, seeing that the carb is adjusted and cleaned as you mentioned. BTW, your E clip should be in the center position, and what pilot jet and main jet are you using? What did the 44mm come off, and what did you change the jets too?
 

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Discussion Starter #14
If both cylinders are within 10% of 110 psi, that should be good. With no gas in the pulse line, the center seal could be ok, but not necessarily. If you had the idle slowly rise and nothing you did made a difference, I would say you have an air leak. Could be the intake leak or a PTO or MAG seal leak.
It really is a funny thing. When I bought the sled a month ago buddy had it running with that carb. I had to put a new track in it and assemble the chaincase. Basically he sold me an engine in a chassis with all the other parts in boxes. Since I’ve reassembled everything I haven’t been able to get the engine going. Couple pulls and the plugs are soaked. Makes sense that the vm44 is way to big. Don’t know what he did before I showed up that made this thing start and idle.
 

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While the 44mm is a big carb, with the proper jetting, it will work. Did you see the engine run with that carb on it? Did you strip the carb down when you cleaned it? I'm not trying to be a turd about this, but anything you can disclose about the engine and carb will help.
 

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Discussion Starter #16
While the 44mm is a big carb, with the proper jetting, it will work. Did you see the engine run with that carb on it? Did you strip the carb down when you cleaned it? I'm not trying to be a turd about this, but anything you can disclose about the engine and carb will help.
I appreciate your help and questions. Yes I saw it run. He had to give it a few pulls. It started, stalled then he pulled couple more times and it ran and idled. He gave the throttle few cracks. Lots of smoke. I assume because he put too much oil in the mix. I drained out and put fresh premium gas at 50:1 when it ran here for a minute there wasn’t all that smoke he had.
I did disassemble the carb. Pulled all the jets/needle. Used carb cleaner and compressed air. The piston needle had the clip on the third from top position. I put it back on the first from top position as a buddy said that was stock. I checked the floats and float needle/seat. Made sure floats work.
 

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Discussion Starter #17
I assume the next question is what size jets/needles in the vm44? I’d have to tear it apart to read the numbers. 6DP60 is what I remember on the needle.
 

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With the E clip on the top of the needle, that is the leanest setting. Maybe with the pilot jet that's in there and if you used the choke, it was way too rich. Your float setting should be set at .66-.74 inches withe the carb upside down, measured from the carb mating surface to the tip of the arms. Now to dry out the engine, take both plugs out, pull it over several times with the throttle held open and let it set for and extended period of time. I don't recommend this, and do it at your own risk, but you can use a stick lighter and slowly turn it over with the flame over the spark plug hole. (Both plugs out.) If that all fails, I would be curious to know what you pilot size is.
 

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Discussion Starter #19
With the E clip on the top of the needle, that is the leanest setting. Maybe with the pilot jet that's in there and if you used the choke, it was way too rich. Your float setting should be set at .66-.74 inches withe the carb upside down, measured from the carb mating surface to the tip of the arms. Now to dry out the engine, take both plugs out, pull it over several times with the throttle held open and let it set for and extended period of time. I don't recommend this, and do it at your own risk, but you can use a stick lighter and slowly turn it over with the flame over the spark plug hole. (Both plugs out.) If that all fails, I would be curious to know what you pilot size is.
I’ll pull the carb apart again tonight and post back.
thank you so much for your help!
I think I’ll just do the first option to dry the engine out. Not a fan of gasoline and flame in an uncontrolled environment. LOL
 
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