SOHC.co.uk Forums > CB500/550

tickover problem

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mickwinf:
For the life of me I can not get a good reliable tickover on my 500/4. Everything is as standard including exhaust, no air leaks new filter, carbs have been cleaned several times, ultrasonically and carb cleaner plus airline. All service items are spot on, bike runs great in all other respects, pulls away with no flat spots and revs up to the redline no problem. I rebuilt the carbs with a keyster kit and set float hight correctly using a special tool. I have tried substituting the original mixture screws but no change. The best idle is obtained with screws 2 full turns out, more than the workshop manual says. When idling at first it seems ok, then after a few seconds it will falter and stop. It also hangs on to the revs slightly when I rev and return to tickover. Also carbs have been balanced with vacuum gauges. Any tips ?

busa:
sounds daft mick.  have you checked your throttle cables are push pulling  ok  and are not restricted anywhere.  I have had problems with newer bikes  (race bikes)  especially Hondas  for this.  similar thing,  turned out to be throttle cables.  Also   is there an O ring on the Mixture screws.   could be that  leaking.

might be wrong.  just a thought.

regards   colin

mickwinf:
Yes Colin cables are new and have a bit of free play, carbs snap shut when throttle closed, its doing my head in!

busa:
the needles are not bent are they?   have you altered position of needles. choke butterflies  screwed on tight (not loose on bar)
sorry mate  just  racking my brains for you.   O rings on fuel link pipes  the ones that link each carb.   or blank ends on the choke arm on the out side of No1  and No4 carb  this is like a little core plug.  Breather on tank,  or filter in tank,   kink in fuel pipe  etc.   timing slightly out.  (advance/retard Plate).  synch screws in tight   inlet manifold rubbers could be leaking(ones that are against the head.  you could test.  when engine running  spray WD40  over them  see if engine revs pick up.   if so there is you leak (I think you would already know this anyway) 

its drawing  air  or lacking fuel somewhere  at low RPM.
hope these suggestions  help

mickwinf:
I have checked for air leaks as that is the common cause of erratic running, all internals are new and set to stock positions. I did think about putting original jets and needles back in but bike runs great except this tickover problem. Will check again for air leaks and report back.

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