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 new 42 mm mikuni floods before turning motor over 
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Joined: Tue Nov 02, 2010 6:47 pm
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Post new 42 mm mikuni floods before turning motor over
I decided to upgrade to the 42mm mikuni kit from bps and the rapid r exhaust on my 35 gtr before the season starts, 2013 model gtr. No matter how I trim the motor the carb floods immediately when I pump the fuel bulb. I swapped the needle and seat to the smaller one included in the kit as recommended in bps instructions. I have done many carb rebuilds and replacements on outboards and and small engines, but also realize that no matter how many I have done things can still be overlooked. float high is set at closed off level float, no adjustment was needed. I cannot think of any other reason than a bad needle and seat that a new carb would flood like that.
Any suggestions would be greatly appreciated.
thanks


Sun Sep 17, 2017 11:47 am
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Post Re: new 42 mm mikuni floods before turning motor over
Hook a pressure gauge on your fuel line and see how much pressure the bulb will actually create. More than likely it is higher than the needle and seat can handle.


Sun Sep 17, 2017 1:18 pm
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Post Re: new 42 mm mikuni floods before turning motor over
Pull the bowl and watch what's happening when you play with the float. Its got to be something easy staring at you


Sun Sep 17, 2017 1:50 pm
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Post Re: new 42 mm mikuni floods before turning motor over
Make sure it's the 2.3 needle and seat.


Sun Sep 17, 2017 9:34 pm
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Post Re: new 42 mm mikuni floods before turning motor over
A primer bulb creates more pressure than needed for the mikuni. I can get gas to flow out my overflow tube as well if I pump the bulb to much. These carbs have an internal accelerator pump and I never have to pump the primer bulb to get it to start. I crank it over and if it doesn't start within a couple revs, I squeeze the throttle lever twice and she fires right up regardless if its 90 deg. or -15 deg. I think you're blowing gas right by the needle and seat.

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Mon Sep 18, 2017 9:35 am
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Post Re: new 42 mm mikuni floods before turning motor over
if you pump the bulb until its HARD, it will overflow the Mikuni.

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Mon Sep 18, 2017 10:41 am
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Post Re: new 42 mm mikuni floods before turning motor over
I have also tried gravity feeding fuel to the carb no fuel pump and no primer bulb it floods as well, I can pull the bowl and flip hold the float up to close the needle and if I blow on the hose it will leak through the needle and seat until the fuel is gone. Once the fuel is gone it seals the air and doesnt leak any longer. this thing is driving me crazy, Needle and seat have been changed to the smaller one included in the bps kit, sent bps pics and they agree that I installed the correct needle and seat.


Wed Sep 20, 2017 10:23 pm
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Post Re: new 42 mm mikuni floods before turning motor over
Any chance of an imperfection in the oring that goes around the seat. Or a scratch or something


Wed Sep 20, 2017 10:54 pm
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Post Re: new 42 mm mikuni floods before turning motor over
It doesn't take much of an imperfection to allow gas to leak past the needle and seat. Double check everything to make sure there is no damage. Check movement of float as well.

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Quote classic by rangerp: "Red seemed to be enjoying herself, and I assume by the look on her face was about to hit the high-note and throw a locate as she treed the possum."


Thu Sep 21, 2017 4:47 am
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Post Re: new 42 mm mikuni floods before turning motor over

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Thu Sep 21, 2017 8:20 am
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Post Re: new 42 mm mikuni floods before turning motor over
got the flooding fixed it was a bad needle or seat I could tap it and get it to seal just didn't want to sit right consistently so I replaced and no more flooding.


Wed Dec 20, 2017 11:55 pm
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