Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: H2Eric on August 29, 2019, 11:16:31 AM
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I would have my CB350f on the road, but its got carb problems. It wouldn't run properly, usually Cylinder No.3 wouldn't fire at all. Then No.2 gave up the ghost. This was traced to the main jets and the 'O' rings, which of course were 45+ years old and petrol was leaking passed the 'O' rings. A new set of jets and hurrah we have all 4 cylinders working. The next snag was that I couldn't get the bike to idle properly. It would idle nicely on start up, perhaps with a tweak on the throttle stop screw, but out on the road at every stop the revolutions per minute would be around the 3000 mark. Leaky float needles perhaps. There was a dribble or two from some of overflow tubes when the tap was turned on, but stopped as soon as the engine started. So, another strip down and new float needle assemblies fitted. A bench test before putting the carbs back on the bike and hey presto, petrol pours out of every possible outlet when you turn the tap on. Oh pooh! or something along those lines. Float needle problems I guess and detritus lurking somewhere despite having the carbs ultrasonically cleaned.
The seats for the float needles (new after market jobs) don't look to clever with the aid of a magnifying glass, but I wouldn't have expected petrol to gush from the overflow tubes, a dribble may be. A new set of Genuine Honda float needle assemblies have been ordered for CMSNL at great expense. Meanwhile, has anyone had similar problems? I'm sure this is not restricted to just the CB350f. Anyone know of a good carb rebuild person(s)?
Eric
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Julie swears by viton tipped float valves, although new ordinary type ones should cure the overfilling problem. I'm assuming you'very checked to float height is 21mm.
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Another tip on here from kevski, was to polish the float valve seat to give a really fine finish for the needle taper to close against.
You could use something like cutting compound for paint and dependant on access use a shaped wooden dowel to dress the surface.
Tickover, if you've got a conflict on the synch mechanism with one fixed carb then it can leave the slides high, so preventing a position that allows correct closing for tickover. Basically they are left partially open even with the tickover set screw backed right out.
Bryanj routine for bench setting will close that one out to give you a reset if you are in doubt.
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Julie swears by viton tipped float valves, although new ordinary type ones should cure the overfilling problem. I'm assuming you'very checked to float height is 21mm.
Nope, never used viton tipped float needless, just viton O rings.Can we actually get rubber tipped needles for our carbs ?
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Sorry, I misunderstood