SOHC.co.uk Forums > CB500/550
CB 500 K1 running issue
Beefington1975:
--- Quote from: McCabe-Thiele (Ted) on September 20, 2022, 09:10:32 PM ---
--- Quote from: Beefington1975 on September 20, 2022, 08:19:51 PM ---Just a thought...saw someone on another thread suggest that engine oil level could be a factor? I've checked mine and it's on the top line. The deposits on the plugs look dry, but could the fouling be due to excess oil???
--- End quote ---
I would only expect a high oil level to become an issue at high engine rpm due to excessive oil misting
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OK. Thank you. I'm grasping at straws I think
K2-K6:
--- Quote from: Beefington1975 on September 20, 2022, 08:19:51 PM ---Just a thought...saw someone on another thread suggest that engine oil level could be a factor? I've checked mine and it's on the top line. The deposits on the plugs look dry, but could the fouling be due to excess oil???
--- End quote ---
As Ted indicated, I stood don't feel there is any effects likely from this. They have more tolerance to raised oil level that this amount.
Wouldn't discount the air filter as suspect though. Any significant impairment with this will impact that mixture and not be readily evident from just looking at the filter. Definitely worth trying with it removed to at least give you a check on condition and flow impact to running. Easy and costs nothing too.
Beefington1975:
--- Quote from: K2-K6 on September 20, 2022, 09:32:30 PM ---
--- Quote from: Beefington1975 on September 20, 2022, 08:19:51 PM ---Just a thought...saw someone on another thread suggest that engine oil level could be a factor? I've checked mine and it's on the top line. The deposits on the plugs look dry, but could the fouling be due to excess oil???
--- End quote ---
As Ted indicated, I stood don't feel there is any effects likely from this. They have more tolerance to raised oil level that this amount.
Wouldn't discount the air filter as suspect though. Any significant impairment with this will impact that mixture and not be readily evident from just looking at the filter. Definitely worth trying with it removed to at least give you a check on condition and flow impact to running. Easy and costs nothing too.
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Ok. Thank you. Will try it with the air filter out 👍
Beefington1975:
--- Quote from: K2-K6 on September 20, 2022, 07:11:26 PM ---Try with the screws set at 2 1/2 turns out and see if that gives anything in the way of sensible running, or improvement at all.
It does appear to be too rich.
Do you know which size of idle jet is fitted to them ?
More rudimentary check is to remove air filter and see if that improves running.
Really just trying to get further assessment to help indicate what may be out of kilter.
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Had some time to tinker today
I removed the in-line fuel filters and ensured the fuel lines were stock length.
I then wound the air-screws out to 2.5 turns and took the bike for spin.
It ran very well, a pleasant surprise. I covered about 10 miles - mostly low speed (30 - 40 mph) with a few bursts of speed (up to 60mph) . No poor running evident. Checked the spark plugs and they seem 'normal'/optimal
Not sure what this means - as it ran much better at a non-stock setting.
K2-K6:
For some reason it seems to be getting just a little excess fuel at the very low end of carb range.
Setting the screws out further will not change the metered fuel from idle jets at their maximum (roughly half way through carb opening) as that's controlled by the 40 sized orifice. What the air modulation does is to change the "ramp" angle leading to that point by bleeding more air through than fuel at the very base of throttle slide opening.
Honda don't state an absolute for this setting of air jet, more a competent start point to be refined during setup. Obviously this case you can see the response from resetting them (indicating circuits are working reasonably) and ending up at 2.5 out is probably at the far end of range reality, but not unworkable. Probably more assessment is valid here to see if you've any unwanted complications and perhaps see if anything else is out of the ordinary over further mileage.
At least if it runs well you've got a chance to now get more comprehensive view.
The inline filters, I'd definitely not associate with low speed fuel demand and feel confident to discount those in this area of carburetor work. Usually it's peak flow that is of concern with these and inadequate supply volume to replenish float chambers fast enough when flat out and wide open throttle. The float chamber of course acts a constant reservoir to the jets and will ordinarily have no problems at low speed.
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