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Hello all,
We can easy buy/exchange exhaust systems and air filters, but what about upgrade of the carburetors ?
I have a lot of questions, please for your support:
Pilot screw set up, affects a bit, 1 up to 2 turns open as Honda & Haynes requirements.
Don’t do above 2 ½ or more !! the O-ring can come out of the cylindrical part of the pilot screw, then when/if you go back it to, say 1 ½ , the O-ring is smashed and doesn’t seal any more.. happened to me at one of them. Without knowing the real reason, I thought I had smashed the taper of the pilot screw, I bought two brand new sets, expensive (!), so, just don’t undo them so much.
Installation: hold the pilot screw vertical, insert the spring, the washer & the O-ring (on the cylindrical part of the pilot screw) and vertically insert and screw all of them together as a set in the carb body.
Slow jet size. On the carbs are #38S, I don’t know what “S” stands for, neither found original Keihin #40S, I found and bought Keihin #40, when I try them, I’ll feedback. Should affect the slow middle rpm I suppose.
Needles , should affect middle range rpm, I tried to lift the needles by adding 1 mm washers on each, I didn’t notice any difference, so I removed them. Any idea how and how much to raise the needles ? any idea for other needles ?
Main jet holder, the needle works in it. If wider, then more flow, I suppose the same effect as raising the needle.
A “cheap” part, (if something goes wrong, just replace them) but hard to measure the internal bore, find such drill and drill them coaxial… somebody knows the internal bore, or done something similar, or exchanged them ?
should affect middle range rpm
Vacuum slider & membrane set Extremely expensive part !!!
Drill the vacuum hole bigger for easier rising of the slider, but if not OK then the replacement is a lot of money !..
Cut a part of the spring, cheaper than the above if you need to go back to the original.
On both above I’m afraid of the “mirror/negative” effect: you throttle it and accelerates easier, but if you decelerate the effect will be slower, or will not decelerate as should . any idea ?
Main jet
For wide open throttle, I don’t ride at WOT for long periods,
does somebody has changed the main jets ? results ?
any feed backs ?
I think that nobody changes only the main jets anyway.
Others ?
The majority of the above is trial/error, I’m looking for cheaper errors…
Don’t try other jets expect Keihin, they simply don’t work. (One of my “cheap” errors...)
I have noticed the following:
https://www.unlimited-power.net/honda/cb500/changing_admission_cb500/parts_shop/4125/1567
has somebody tried this specific upgrade kit ? requires drilling of the vacuum slider, but provides different springs (!)
Best regards
Panagiotis
We can easy buy/exchange exhaust systems and air filters, but what about upgrade of the carburetors ?
I have a lot of questions, please for your support:
Pilot screw set up, affects a bit, 1 up to 2 turns open as Honda & Haynes requirements.
Don’t do above 2 ½ or more !! the O-ring can come out of the cylindrical part of the pilot screw, then when/if you go back it to, say 1 ½ , the O-ring is smashed and doesn’t seal any more.. happened to me at one of them. Without knowing the real reason, I thought I had smashed the taper of the pilot screw, I bought two brand new sets, expensive (!), so, just don’t undo them so much.
Installation: hold the pilot screw vertical, insert the spring, the washer & the O-ring (on the cylindrical part of the pilot screw) and vertically insert and screw all of them together as a set in the carb body.
Slow jet size. On the carbs are #38S, I don’t know what “S” stands for, neither found original Keihin #40S, I found and bought Keihin #40, when I try them, I’ll feedback. Should affect the slow middle rpm I suppose.
Needles , should affect middle range rpm, I tried to lift the needles by adding 1 mm washers on each, I didn’t notice any difference, so I removed them. Any idea how and how much to raise the needles ? any idea for other needles ?
Main jet holder, the needle works in it. If wider, then more flow, I suppose the same effect as raising the needle.
A “cheap” part, (if something goes wrong, just replace them) but hard to measure the internal bore, find such drill and drill them coaxial… somebody knows the internal bore, or done something similar, or exchanged them ?
should affect middle range rpm
Vacuum slider & membrane set Extremely expensive part !!!
Drill the vacuum hole bigger for easier rising of the slider, but if not OK then the replacement is a lot of money !..
Cut a part of the spring, cheaper than the above if you need to go back to the original.
On both above I’m afraid of the “mirror/negative” effect: you throttle it and accelerates easier, but if you decelerate the effect will be slower, or will not decelerate as should . any idea ?
Main jet
For wide open throttle, I don’t ride at WOT for long periods,
does somebody has changed the main jets ? results ?
any feed backs ?
I think that nobody changes only the main jets anyway.
Others ?
The majority of the above is trial/error, I’m looking for cheaper errors…
Don’t try other jets expect Keihin, they simply don’t work. (One of my “cheap” errors...)
I have noticed the following:
https://www.unlimited-power.net/honda/cb500/changing_admission_cb500/parts_shop/4125/1567
has somebody tried this specific upgrade kit ? requires drilling of the vacuum slider, but provides different springs (!)
Best regards
Panagiotis
