11.90 motor with 33 carb sleeved down dies on take off

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11.90 motor with 33 carb sleeved down dies on take off

Postby Callahan1529 » Sun Feb 04, 2018 12:32 am

We just switched to an alcohol engine. We have an 11.90 motor with a 33 carb sleeved down. When the engine is on the stand and the clutch belt is off, we can get the car to run and car does great when given the gas. As soon as you let off the gas, it sounds like it pulsates and the engine sounds go up and down as if you are giving it the gas and letting off over and over.
If you take the car off the stand, then put the belt on, the clutch grabs hard when it engages and the motor will cut off. We started with a polar, just switched to a shock wave that was set up for an 11.90 motor. Still the same issues. At first both clutches squealed and the belts were loosened. Now there is no way the belt is to tight. The squeal is gone, but the killing the motor, clutch engaging hard when on the ground and pulsating when ran on the stand when letting off the gas is still there. Any suggestions on how to solve these two issues?

Thanks
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Re: 11.90 motor with 33 carb sleeved down dies on take off

Postby Kern Family Racing » Sun Feb 04, 2018 10:49 am

Pull your plugs and check the timing mark and see if it looks like it is running too lean/rich. There are posts on how to read methanol plugs if you are unfamiliar with doing so. My guess is either a vacuum leak on the intake or the jets are too small causing it to be lean. It sounds like your main jets are too small so when it transitions off the pilot it goes lean and dies. Post your jet sizes on here and that will help.
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Re: 11.90 motor with 33 carb sleeved down dies on take off

Postby RNorton » Sun Feb 04, 2018 12:37 pm

Surging is generally an indication of being too lean.
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Re: 11.90 motor with 33 carb sleeved down dies on take off

Postby jtracr » Sun Feb 04, 2018 12:44 pm

X2 on too lean or vacuum leak. As for clutch you need lighter arms or stiffer spring. The low HP of the little motors need to be up just right in the power band to get the weight moving from a dead stop. I have also seen a belt too LOOSE do the same thing. With a loose belt it will rev up at the hit but by the time the belt bights it is too far down the arm and basically into a higher gear, thus pulling the RPMs too low.
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Re: 11.90 motor with 33 carb sleeved down dies on take off

Postby Pool Man » Sun Feb 04, 2018 12:55 pm

I would take care of the surge problem first off.
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Re: 11.90 motor with 33 carb sleeved down dies on take off

Postby Ten5TireDad » Sun Feb 04, 2018 2:24 pm

The squeal is either a tightness or alignment issue.
Like it's been said a surge is caused by a lean condition. What rpm are you trying to idle it at? If you're starting at 1,500 and then engaging the clutch and expecting it to idle that low it's not going to.
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Re: 11.90 motor with 33 carb sleeved down dies on take off

Postby Ben Bear » Wed Feb 07, 2018 1:20 pm

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