SOHC.co.uk Forums > CB350/400
A couple of "tune up" questions...
K2-K6:
To check sparks for each cylinder on these, you may need to flip the induction clamp for the difference in each pair of coil leads from single coil to get signal. They are inverted in comparison to one another as exit each end of that coil, with some clamps directional and need that flip flop to get a read.
I think it's worthwhile at this point to see if you can chase it down. Easily said by me not doing the work :) as it's good to have them glitch free, which they should be capable of. Satisfying too, if you get it completely debugged and they are usually very linear in smoothness from their original design intent.
Hopefully you can get a clearer picture as you test the different elements.
McCabe-Thiele (Ted):
At the risk of sounding naive you mention it's a low speed stutter - is it possibly a feature of an engine that always needed revs to perform & run smoothly?
Not so much a stutter as low revs death due to a lack of low down torque - as has been said previously opening the throttle wider often makes it seem worse? I guess it might be a question of degree especially if the bike has run without the stutter previously.
Mikep328:
All the spark/timing tests were good. I didn't pull the carbs today...just couldn't get up the enthusiasm...maybe tomorrow.
The stutter/roughness I am speaking of occurs just above idle - 1500-1800 RPM. It is most apparent if holding a steady throttle in that range - say 1st or 2nd gear in slow-moving traffic or maneuvering in a parking lot.
garyjpaterson:
--- Quote from: Mikep328 on September 17, 2023, 02:21:14 PM ---The stutter/roughness I am speaking of occurs just above idle - 1500-1800 RPM. It is most apparent if holding a steady throttle in that range - say 1st or 2nd gear in slow-moving traffic or maneuvering in a parking lot.
--- End quote ---
I have it in both my CB350 twin and CB750, I've yet to be able to tune it out. Maybe a little faster, 30mph in 4th gear is the when its most noticeable, just when you crack the throttle it doesn't like staying there. Give it a fistful and away it goes
Mikep328:
Pretty much the same symptoms!! I was thinking it was my #1 carb idle circuit since it doesn't respond properly to the movement of the airscrew. I'm going to try to remove/clean out that jet with the carbs still on the bike. I squirted carb cleaner through all the jets when I had everything disassembled but I didn't actually check with a wire to be sure the idle jets were totally clear - stupid on my part. But I'm only checking #1 since the other three react properly to airscrew adjustment.
Removing the carbs/ raising the needles is the next thing I will attempt.
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