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1978 CB750 F2

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blackeagles:
I have been trying to sort out a problem with my CB750F2 carbs and was recently told they are PD42a but I have just noticed mine are stamped PD41B.  Anyone know what, if anything, is the difference and will it affect setting them up as per book i.e main=105, slow running=35 and a setting of 1 3/4 turns out etc??

Bryanj:
Dont think the settings vary, needles and adjustments do.
Both are a real PITA unless bike used at least weekly, the press in pilot jets block for a pastime.

blackeagles:
"the press in pilot jets block for a pastime" - I guess I am lucky as when I took the carbs off and 'fired' cleaning fluid into all the jets they were clear!!

K2-K6:
The A version is F2 fitment,  B is for K7.

They are paired in one manual from Honda but obviously the engines differ in spec.  Valve size,  cam,  compression ratio differ between the two so they seem to respond to that spec by slight carb differences.

Mains are 105 idle screw 1 3/4 out (F2 PD42A) and 110 for K7 B fitment with 1 1/2 out for idles.

Unsure of what they changed between A and B spec but thought it was different cutaway on throttle slide to go with lower rev / torque curve on K7 versus the F2.

They don't state in their manual the idle jet size,  or if different needle profile is fitted to them.

blackeagles:
ok, so I seem to have the wrong carbs on the bike.  I will have to take them off again and check the sizes of the jets (which I did not do the first time) when I have time

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