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Needles and seats


Sheeba711

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I have a 7 mil cub with brand new 41 mm mikunis and at test and tun the other day my carbs would leak out the over flows so bad that it was flooding the motor on bottom end couldnt get off the line but when she finally lit she took off is it possible the needles are to big they are 3.5 im contiplating runnin 2.5s it mainly only leaks after you have it running anyone ever have to change needle sizes?

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If you are gravity feed you just need to set the floats to shut off the gas when the float "floats". If you are running a pump then you may need a small seat. If you have billet bowls make sure the float doesnt rub or hang up on the side or edge of the bowl.

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I have tried asjusting the floats even to the point where I thought it was shutting it off to early and it still floods the motor out and runs out the overflows .. It is gravity fed.. I just dont under stand I cant see anything wrong with em and I cant blow through them with the carbs upside down I just dont know what else it can be

 

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If the float height is correct but it still overflows gas you may need to replace the needle valve and seat. The seat and valve can get worn and cause the float to stick. The tip of needle is made of a special rubber wich can harden with age and also cause sealing issues, You can try cleaning it as just a granule of dirt caught in the seat will keep it from sealing.  I would just replace them on both carbs, check float height and seal them back up and be done with it personally.

 

Usually a few taps with the handle of a screw driver on the float bowl will get it to stop leaking momentarily.

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Viton IS synthetic rubber which is the rubber i spoke of. the very tip should be composed of it.

 

Missed the being brand new part at first... If the carbs are brand new the seats shouldnt be worn and sticking/leaking but obviously not impossible.

 

I would guess improper float height or debri in the seat area.

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take bowls off.  put fuel to the carbs  hold floats closed  see if its coming from somewhere else./  if not  take the needles AND seats OUT and make absolutely sure you dont have debris in there.    ( if carbs are new)  

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