SOHC.co.uk Forums > CB350/400
A couple of "tune up" questions...
McCabe-Thiele (Ted):
Might be worth checking both anyway to see if they match.
At the moment my 500 will retain points until I am happy with the way it runs - then I might fit the Electronic one I bought from Bryan.
There is a lot to be said for roadside fixes that points can accomodate. That said points were a pain on older cars.
K2-K6:
Interesting to see if tge ignition check turns up anything unexpected. They are usually reliable though.
A thought, are you running on E 10 fuel ? as that may influence your jetting and may push you up on needle position to regain parity.
Also can be worth a try as it's a quick-ish change, drop the plug gap to 23 thou to see if that has any response or verifiable shift in the effect you are getting.
Mikep328:
Thanks, I changed the gap on the old plugs to .025" before replacing with the new plugs, which I gapped at .030." There was no difference in operation. After doing that I checked all the air mixture screws for the position they were in after "optimizing" them last week. Cyls 2,3 and 4 were around 1 1/2 turns out. But cyl 1 was only 1/2 turn out. If the screw was bottomed, that cylinder would cut out completely but from about 1/2 turn and beyond there was no change in RPM or smoothness. So despite disassembly/cleaning, it appears there is still some obstruction in that carb's idle circuit. :(
Fuel is E10.
K2-K6:
Agree that the question mark over that single idle circuit is probably going to cause you more work :-\
Hard to get an clear evaluation without containing that really, unfortunately.
E-10 has approx 10% more oxygen content. So 10% of 10% E gives roughly 1% increases in oxygen to make it run a small amount lean, in comparison to it's original factory setup.
With that in mind, and while the carbs are off, it could be valid to then lift needles in targeting this overall review of running competently. Depends on your personal assessment of it though.
If that were to be run like that it would likely still be contained within an air screw tweak. Just that it'd fatten up the mid to low response to help you out there.
Mikep328:
Today I'm going to check the spark delivery on the 4 cylinders and also check/verify that the E-ignition timing of cyls 2 and 3 agree with the timing of 1 and 4. Following that I guess I will pull the carbs. We'll be out of town most of the week so probably won't get them back on the bike till next weekend.
I admit there is a part of me that is thinking that since the bike runs great except for the stuttering in a rather narrow, low rpm range, why not just leave it alone? But the major part of me says, "No, I can't deal with that!"
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