Topic: 77 cb750 f2 rinning rich?

[Ed750]

After many attempts engine is running smoothly and idles. Now problem is muffler end is black and will not accelerate going up hill.
Going 70 up hill and try to pass. Twist on throttle and nothing happens. Nothing!
Bottom end power seams fine. New plugs, coils, wires and timing looks spot on.
If running rich can it be leaned out by a simple adjustments as carbs were just redone to stock specks.
Thanks for any help, Ed750     

[jgger]

Is your timing advance working properly? And your fuel level correct.

If the carbs are "fresh" rebuilt, then do the clear tube test. That's all I got.

[HondaMan]

If I can ask a question or two:
What carb kits were used? If they were Keyster and you installed their jets and needles, it is running too lean in the midrange RPM (and higher) from those parts. Their needles are too thick, and their jets are non-Keihin type, which run about 10% leaner than the number stamped on them.

Are you using the stock airbox? If so, do you have the long vent tube for the carb bowls routed up behind it, or up under the seat, to ensure good float-bowl air pressure when running at speed?

[Ed750]

Float levels are good. Timing advance is working correctly
Not sure what brand carb rebuild kits were but they were from Japan if that means anything.
Air box and filter are stock.
Need to check on carb vent tube

[2wheels]

Did you down shift to bring the RPM up?
Going up hill and just rolling on the throttle may not have much effect in 5th gear.  Especially if the bike is loaded up, carrying 300 pounds plus.

[HondaMan]

Did you change the needles in the carbs to the new ones in the carb kits?
Keyster is also in Japan, and the carb kits that others have sent me with their carbs, marked "Made in Japan", contained Keyster parts. The Keyster needles are too thick, so they cause lean running at hiway speeds

To check this, try to pull the choke on a bit when struggling "up the hill" and see if it helps. If so, put the old needles back into the slides. On those carbs this can be done in the bike (although #2 will be tricky).