Question about Honda CB 750 Motorcycles

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I have a 82 honda cb750f. The bike runs fine with the choke on full.But with it off it pops and kicks. The tank is clean,the carbs are sinked.The carbs are clean in the bowl area.The previouse owner took this apart and I think that something went together wrong. The main jets are 100's and the air filter is clean,as well as the plugs.Has good compression and the mufflers are not plugged.I do not know what the dials under the throttle throats are for or ahat they should be set at.they are all out 2 turns from seated.Any help would be great

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  • awc8473 May 10, 2009

    I think they are off a different bike-do you know the idle jet #'s as well? the guy was a tinkerer-all the boots were glued-he thought there was a vacume leak-I sprayed it all with starting fluid and no change in idle.And what are the dials under the neck for? they are right next to the intake boots and have large silver caps over the brass

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Standard jets for the CB 750 are 120's, popping and kicking are usually due to running lean which is probably why it runs great with the choke on as that riches it up. I've run 115's with no problem but 100's??? Maybe was trying for better fuel mileage when gas was $4.50 a gallon?

Posted on May 10, 2009

  • rjbeg123 May 10, 2009

    My '82 DOHC engine has an idle screw adjustment, mine is set about 1 & 1/2 turns out, If you have idle jets then you might not have a Honda Carb? Not sure from description what the dials are? Unless he put some odd caps on the linkage adjusters?

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According to the Haynes manual, post 1980's CB750F's had stock jet sizes 68 and 100...so it sounds like you're probably fine there. Also, the pilot (idle) mixture screws on the on the bottom of the carbs only really affect the mixture at idle (1 1/2 turns out is a good starting point). The most likely reason that you're running lean is that, while the float bowl areas are clean, there are blockages in the jets/passageways through the carbs. You really can't clean these carbs enough. So my advice would be to spend some quality time cleaning.

Posted on Sep 08, 2012

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1 Answer

My honda cb750f will not run without the choke being out


Vacuum leak.

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2 Answers

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Use a couple of cans of Sea Foam.. best stuff in the world.

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