Carburetor stumble in hot laps

[money17]

Carburetor wants to stumble for a straight away and a turn then clean up in first set of hot laps. The rest of the night carburetor is great. We have tried it with motor cold and also warming it up to 190 degrees before hot laps. The fuel pump is a kse tandem on the oil pump. No problems in lines or pump as we have checked. Float level is right. Just wondering what might be the cause?

[Punisher88]

Most likely just loading up. Rev the engine a few times and clear it out before they go green.

[billetbirdcage]

This days most are but I'll ask anyways are you using a top feed type fuel cell? Did you have a bottom feed cell before when you had no issues with it?

I've had issue's in the past with KSE pumps not wanting to pull fuel out of a top feed cell, but the problem was more consistent then what your describing but still erratic thru out the nights. It would usually show up off the corner and fuel pressure would drop also, it was more when the car had high G loads on it both sideways and front to rear like from mid corner to the edge of the corner exit then come back mid straight a way.

[TheJet-09]

Mine does exactly what you're describing...top feed fuel cell with a Carter pump. I've always just considered it normal. While I would never claim to be an engine guy, I do believe that coolant temp gained by an engine running at idle is not an accurate reflection of cylinder temp, which is most likely gained/stabilized only under a load (i.e. - efficiently burning the fuel). But I could be wrong.

[rakracing]

have this problem from time to time, we run methanol , when this happens I pull both needle and seats clean and spray with wd-40 , no more problem, usually happens after a week off

[TheJet-09]

^^^ That's interesting! I run gas, but my work schedule only allows me to race every other weekend. Something to look at.

[billetbirdcage]

The weighted needle below the squirter in the carb often sticks with alky but can happen with gas, causing the squirter to not pump fuel. Often a simple tap with a screwdriver handle or something is enough to jar it loose and work. This happens more often when the car sets for a week or more between races so that is something to look for, just remove air cleaner and move throttle and make sure the accelerator pump is working.

It's possible that once the car runs and bounces around on the track or you pump the throttle enough it comes unstuck and starts working thus causing your one lap hesitation.

[taylor2727]

Could b plugs dirty from starting without getting up to temp (like running in garage) and takes a lap to clean them up and runs better