SOHC.co.uk Forums > CB500/550
sluggish 550
K2-K6:
Well that is good news that the motor seems ok.
At that revs and with throttle wide open it's mostly pure main jet running as I understand it with the height of the needle controlling when it gets to max flow as you open the slides more, i.e. if you raise the needles then it gets to max flow a little earlier but doesn't increase the total. If you raised the needles (and this was the fault) you'd expect to see some increase in the faltering revs, if it gets better then you'd have to consider going up in main jet size and bringing the needles back to the central position.
One thing we haven't gone over is the breathers into the float chambers, if these are blocked at all then it will run lean at high demand as you need free air to get in for the venturi vacuum to draw fuel out at
the correct rate.
mickwinf:
k2-k6 this is one thing i had not considered where are the breathers?
z1100r:
You are setting the carbs up to the right manual aren't you...not the Haynes manual with the 500 carbs in.
http://data.sohc4.net/SM500/HSM500550_16.pdf
mickwinf:
well guys i have found the problem and sorted it!! Believe it or not all it was was a float needle! the little sprung rod that contacts the float was stuck in place on no 2 cyl, all that trouble for that!! now it revs like a good un, thanks for help everyone.
K2-K6:
Sometimes it's something small like that that's missed, it just shows when discussing jetting etc how such an insignificant looking device can have a huge effect.
Good you found it though, should get some decent time out on it during the summer now.
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