642b acts like it runs out of fuel under a load

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gsxrking193

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Feb 2, 2015
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carb has been rebuilt fresh tuneup. runs and idles fine revs good but when i put it under a heave load it starts to die and usually backfires (lean condition) and if I let out of the controls it will pick right back up and run good til I put it under a heavy load. any help thanks
 
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gsxrking193

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Feb 2, 2015
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fuel filter is aftermarket inline where is the brass one located. and new to the machine how are the aux hydros engaged?
It doesnt miss a beat until under a load when a demand for fuel is present the very expensive carb kit didnt have and accelerator pump kit in it wondering if that could be the cause
 

antfarmer2

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Oct 28, 2013
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fuel filter is aftermarket inline where is the brass one located. and new to the machine how are the aux hydros engaged?
Ok sound like your aux hydr lol ........the right stick moves back and forth make sure you keep it in the middle.....first thing with this one you want to do is check and grease the ujoints if they go can cost more than its worth
 
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gsxrking193

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Feb 2, 2015
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Ok sound like your aux hydr lol ........the right stick moves back and forth make sure you keep it in the middle.....first thing with this one you want to do is check and grease the ujoints if they go can cost more than its worth
ok I will check it tomorrow any way to disconnect cause I have no other attachments other than the bucket
 

reaperman

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Dec 18, 2011
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Does that machine have points yet or have you converted to electronic ignition? The points may be out of adjustment. I had a 642 and when it started running funny, it was time to adjust them too. With a backfire, have you changed your distributer cap, it could have a crack.
 

jerry

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May 3, 2007
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Does that machine have points yet or have you converted to electronic ignition? The points may be out of adjustment. I had a 642 and when it started running funny, it was time to adjust them too. With a backfire, have you changed your distributer cap, it could have a crack.
It does sound like the timing or point gap is way off or the vacuum advance is bad or rusted up. I had a 632 and when the points got out of adjustment it would act like that also.
 
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gsxrking193

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Feb 2, 2015
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It does sound like the timing or point gap is way off or the vacuum advance is bad or rusted up. I had a 632 and when the points got out of adjustment it would act like that also.
It has aux hydros. points cap rotor and plugs are new anyone have timing specs for it what degree it should be and dwell setting i set the points at .016
 
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gsxrking193

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Feb 2, 2015
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Verify ignition is OK first. Probably the govener is the problem.
pulled the inline fuel filter and it was full of debris I replaced it and the new one had alot in 5 mins run time. at idle the sight glass on the bowl will be full but under a load it empties quickly. I am going to replace the pump and clean out the tank. ignition is fine evrything brand new. timing was dead on
 

antfarmer2

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Oct 28, 2013
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pulled the inline fuel filter and it was full of debris I replaced it and the new one had alot in 5 mins run time. at idle the sight glass on the bowl will be full but under a load it empties quickly. I am going to replace the pump and clean out the tank. ignition is fine evrything brand new. timing was dead on
On my 743 there is a channel on the back of the fuel tank for the fuel line to go through when the line gets old it can shrink and get pinched off also the pickup line can crack or the screen can get pluged
 

antfarmer2

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Oct 28, 2013
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On my 743 there is a channel on the back of the fuel tank for the fuel line to go through when the line gets old it can shrink and get pinched off also the pickup line can crack or the screen can get pluged
The pickup line is in the tank
 
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