Purchased a '75 CB400F from a freind (who I trust and who is a very capable mechanic).
Bike had been sitting for about 1 year, garaged.
Upon fueling and running- had traditional drippy carbs (needle valves) and didn't want to idle well. He said it was running well when put away (and I do trust this person to know and tell the truth).
Cleaned the carbs - Expecting that to solve the problem. Has not - in fact, getting worse.
Has not (and we are both experience and both somewhat baffled - I've had several other SOHC 4's incluing a '73 350F.)
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Current state
- Bike idle is 'questionable' - may idle (rough and not nice), or roar (2000 rpm) or die.
- Seems rich (by smell).
- Running with idle screws way in - 1/4 turn out rather than the 2 +/- 1/2 recommended.
- Occasional carb overflows.
- Cruise is "burbble"
- Accel has some misfires.
- Stock air filter (have not run with it out - will do so).
- Close to stock exhaust (muffler is different).
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What have I done:
- Pulled the carbs off and cleaned the bottoms (main jets, needles, idle jets). Really not that dirty.
- Run several tanks of clean premium fuel through it
- Checked:
- Valves - all good
- Cam Chain - tightened
- Carbs syncd
- Timing set (problematic - see below).
- Adjusted carbs (running at 1/4 turn out - not 2. 2 - smells RICH).
- May have vacuum lead intake #3 but not clear. Very small change in running on spray of starting fluid.
- Done all this multiple times.
Plans:
- Have Carb kits ordered
- Have Dyna S ordered.
- Re-clean carbs.
- Pull tank valve filter and look for crap.
- Ask for help!
Timing Woes: Timing this beasty is very hard as the base plate seems to move back and forth right and left. When you set dwell (gap) then try to time it, if you let the baseplate move, then your dwell is all wrong. I set dwell and timing by holding base plate right - but I can only do static timing, if I try a light, it bounce around. Then to get 2-3 points timing right, I have to close the points up a bit from where they should be.
Hoping the Dyna S will solve this.
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Bob