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need help with popping on line

1741 Views 11 Replies 7 Participants Last post by  mudracer1978
i ran yesterday and i am having an issue with the motor popping and cracking on the line. i dont know if it is in the two step or the carb? has anyone had any problems with a msd two step box? once i get half track or so it sounds good and i cant hear any popping but i cant leave the line worth a crap. anyone with any ideas carb,convertor,two step, or anything else please help.

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Popping? Through the exhaust, intake or where?

mine would pop when holdin the throttle around 3000 or more... so i turned my oem distributor and it went away.... just sayin?!
here is my pass from a couple of weeks ago dont have one from this saturday yet. that is what it still sounds like on the line. i have my two step set on 4200 and i couldnt get it much over 3000 saturday.


Kinda hard to tell. But it sounds like it kinda started out ok then got worse?

I watched it several times and it looked like the bumps really threw it into fits? Did you get that at all by driving it. It seems like it holds up a bit then lets out a big "pop' or "bang"!

But I kinda associate it with he bumps from this particular video.
If that were the case. Could the float be bouncing causiong too much fuel to come past the needle and seat? Maybe an off road or spring loaded needle and seat? Yo would know better than I from where the problems started but it looked like you had your most RPM's out of the start and on the first part of the track until you started hitting the bumps, then it gave up pretty quick. I could be wrong!

Let us know what you find!!

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Could also be the fuel level is running a little high then when you hit the hard bumps it sloshes out the vent tube(s). I've had that problem once and fixed it with one piece of fuel line long enough to put a little bend in it with each end shoved down over each vent. Then cut out a hole on the top of the fuel line on both sides of the air cleaner stud and zip tie it to the air filter stud.
another pop and bang stage i personally went through was when i put the exhasut gaskets on backwards andblocked the exh. ports quite a bit... flipped them around and it solved it. to much backpressure eh
I just had a very similar weekend. I could rev it up at the line, sounded right, up to 6500 no prob. As soon as the light went green, POP- SPUTTER-POP, all the way down the track. Didn`t have time to troubleshoot during my class, so i just had to deal with it and lose. So changed jets down, and entered into the pro-stock class, same results, but not quite as bad. Still lost. Then i took out all the plugs, checked all the wire connections, ground, pulled fuel lines and checked for flow. All looked good. Got in my truck, Stalled it to 4000 in gear, and thought" I fixed it" So i ran over to the booth and entered into the pro mod class, just to see if it worked( wife wasn`t impressed) . Seemed to clear up 90% But now against the big dogs, still lost, and still popped a little. Went home rebuilt the Dommy, decided to haul it out for a test drive in a field. Well now it wouldnt start, noticed the light on my 6AL-2 was flickering, I reached down and wiggled the harness, and it went solid on. Found that the pin on the msd harness was falling out the back side of the square connection, so the bumps in track was making it lose connection. Damn! all this for a 1 second fix......Just wanted to share my pain;) It`s running like an animal now!
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Here is another pass. May not be the carb but I still kinda think it may be associated with the bumps. Maybe loose connection wire as Stitches suggested or still may be fuel slosh!
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Check your grounds, also sounded like it didn't like the 2nd gear shift.
on the first pass at this race the humps i think sloshed the fuel around and made it stall out but on the other two passes it was the driver letting off because the steering was broke and i probably should havent ran but didnt think it was that bad till i realized it was going to go where it wanted to. im still not sure why i cant get it to stall on the line over 3000 but now the brakes are not working so i have to figure that out before i can test anything else.
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