SOHC.co.uk Forums > CB350/400

Problems after bench sync of carbs

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watty51:
This is a good one...

After bench synching my carbs on a cb350f yesterday using this method I found on this post :

LOOK INTO INLET SIDE AND YOU SHOULD SEE THAT EACH SLIDE HAS A GAP OF ABOUT 1/8"
WIND THE IDLE SCREW IN ( RAISES ALL FOUR SLIDES) UNTIL THE DRILL SHANK 1/8" JUST SLIDES UNDER THE LOWEST CARB THEN ADJUST ALL TO SAME HEIGHT.

ONCE FIRED UP ADJUST THE IDLE SCREW TO GET TICKOVER.

So did all that, put carbs back on with standard air box with new soft rubbers and now the bike wont idle at all, in fact whats happened is the choke in the upright, on, position (butterflys closed) wont start the bike and doesnt rev to 3000 - 4000 but if you put choke lever in lower position (butterflys open) it revs up to 4000-5000 revs. As soon as you move the lever to slow the revs down it just stalls. It seems the wrong way round.

Only took off carbs originally to check float levels as one was leaking but they are all fine now. Bike was running ok before this. One step forward and 2 two step back.

PatM:
If I recall, i didn't follow that guide/procedure and settles all 4 slides so they were FULLY closed- that way the idle-circuit (which i believe is independent of throttles) operates. Then once started- adjust throttle-stop screw to achieve a reasonable idle and warm up/sync carbs off the gauges.
Ive certainly had the carbs causing the bike to rev-up to an unhealthy rpm, but dont remember the cure- in fact, i think my  re-jetted 'spare' bank do that.
ill be interested to see the replies as Ill try (if it accords with my knowledge) whats suggested.

Ive always had an issue starting my bike form cold- and never once its been started or warm.
On start up, it runs on 3 then the 4th comes in...pop, pop in the silencer- No 3 (which is the problem carb or cylinder) exhaust is cold until fires..Ive tried everything i know.

K2-K6:
It's usually the one fixed carb that catches out setup routines I think,  often number two which you have to match the others to.

Bryanj:
Sounds like you have adjusted the slide openings so that they do not close fully. you need to unadjust all the slides so that they touch the bottom on the flat side with the tickover screw wound all the way out so it nearly falls out. then screw in the adjuster till one slide starts to open and use a drill shank as a feeler to set the others to that point 1/8 is WAY to big use a 1mm or even smaller. When all set unscrew the tickover screw again to make sure all slides touch bottom

watty51:
Thanks for all the replies. I will give all above mentioned a try next week and give you some updates.

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