SOHC.co.uk Forums > CB500/550
idle jet differences , 069's
fogrider:
OK, it's not a usual thing to do, but it likes it, no side effects, just runs better. I think it confirms the mystery weakness at the bottom end. All 4 plugs are identical colours so whatever is causing that weakness is built in, not like one faulty carb.
I altered the slides to 2.2 from 2.5 and there is hardly any difference. I'm halfway through fitting the Lambda sensor and reader. What that shows will be very interesting.
Next few days.........
K2-K6:
It'll be interesting to see the results of AFR monitoring, I like investigative things to clarify what you are getting.
Flat spots are always going to be a "non burn" or partial of the combustion content, and usually too lean. Maybe getting close to 14.7 to 1 or just over during that acceleration phase.
The compression would add more to the analysis I feel, especially if it's stood for some time as the rings are often stuck on examples seen here.
Maybe worth running with the breather pipe submerged in a glass of oil too as they can suck air from crankcase on induction stroke to give unmetered air content in cylinder. It'll draw the oil into the cases if it's got poor sealing.
fogrider:
Lambda sender fitted and have had a run about. When fully warmed up, stopped and read the idle, slightly rich. ( on return, I turned the air screws out to between 1 .1/2 to 1.3/4 turns out from 1.1/4 which now reads right ).
Shocking to see that from even the slightest opening of the throttle right up to half open, the weakness was off the scale.
From half throttle on, goes well rich ! I had bought an aftermarket carb kit, fitted the float valves as mine were shot, left the idle jets in, left the needle jets/emulsion tubes in but fitted the new needles. Fitted the main jets as they had new O rings on but were marked 98, whereas the old ones were 105. From the results, I can only assume there is a serious discrepancy with those needles ( in clip 2 the same as original ) and there is almost no transition from idle to needles via the slides.
I'm sure the mains should be 98, had someone already put 105's in hoping to cure weakness ? or is it just the new needles ? Carbs to come off again, old needles back in. Test run again next week.
Bryanj:
Afterarket needles are notoriousy inncorrect in both diameterand taper, clip position is usually middle and i thought mai jet was supposed to be 100
deltarider:
His is an 'F' that had 98. Below an overview of the oldstyle carbs on CB500/550. Feel free to comment and/or suggest corrections.
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