js440 wont stay running

[DustinJ]

i just did a top end rebuild on my 440 and fired it up idles for a min then if you give it any gas it just dies like its sucking too much air and not enough gas. suposedly the carb has been rebuild. thanks guys, Dustin

 

[DustinJ]

also if i pull the choke it runs a lot better. any ideas what could cause this? thanks, Dustin

 

[onedumbtrucker]

Not enough fuel. Something is wrong with your fuel delivery. Could be the carb needs tuning, could be bad crank seals (not enough pulse pressure to pump fuel), could be air leak or clog in your fuel line/filter/tap, could be the carb was rebuilt badly, assembled wrong or needle valves were not put back to previous or factory specs.

Put your needle valves back to factory settings,
Pull the pulse line off and put your thumb over it while cranking the engine over, (can you feel a strong pulse)
Remove and clean all fuel lines and fuel filter, also look for cracks in fuel lines or other possible air leaks,
Check tank pick up tubes for cracks,
Check fuel line routings, also look for kink in fuel lines.

If it is not one of those things then the carb was probably rebuilt badly or the crank seals are bad and you will probably have to check pop-off pressure in the carb and pressure test the engine.

Hope this helps,
Dan

 

[DustinJ]

Thanks so much!