Hello everyone ....when my bike is running.Ever so often at idle or going down the road.the carb will spit a burst of fuel out the main jet and dam near kill the motor.does anyone have any idea what would cause this problem?I just rebuilt the carb the accelerator pump boot was shot.I fixed one problem, but this one i have no idea no this one

 

not trying to be a smart ask but how do you know its the main jet doing that

to me its a lean condition - low speed jet is semi clogged fuel today is garbage - IF you have had the bike for a while and this problem just showed up - and or the intake is leaking, BUT my guess you must have re sealed it when you had the manifold off, i would re visit the manifold O or flat rings may not be sealing correctly just to be sure - than put a new what ever is in the carb now low speed and see what happens -- johnjzjz

 

With the bike idling i removed the air breather and you can see fuel spit out the main jet Nozzle. its so much when it happens.if you put your hand in front of the carb with the breather off your hand will get wet

 

I have never seen a good working keihin on a harley!

That is the first thing I change on a old harley right there with points!

Often times people think that clearing them and rebuilding them will help and it will never fix it for good! Check the carb shaft if it is loose and moves up and down it will suck air and pop no and than!

My best advice is toss it out and bolt on something else! S&S E is a good carb that most anyone can make work good!

A CV is also a good shovelhead carb, HSR is as well! In the end it will run like a different bike

 

I agree with Ashovel keihin = door stop that thing will drive you crazy

 

I fought the old AMF and Keihin carbs and have way too many drawers of jets as a result of never getting them right. The last was fought for 3 years then replaced it with an S&S Super E and never looked back.

 

Okay, I understand what you are saying.
What you saw was the reverse flow through the carb drew fuel up through the main jet nozzle in the carb bore. Much like it will under normal high speed operation.
So the problem is not that it drew fuel up from the main jet, the problem is that it sneezed.
As johnjzjz said, it is usually a lean condition that causes that.
I ain't a carb expert. I am sure that an experienced carb man could fix or minimize that problem but my vote would be to replace the carb with something along the lines of an S&S E or one of the others suggested by AShovel.

 

Go with the CV best darn thing I ever did to my shovelhead,goes great,,idles smooth

 

 

Another vote for the CV. The difference is like night and day.