Syncing carbs

[Ichy]

One of those where you keep going around in circles.

I've finally rebuilt the CBR6 and decided to sync the carbs. Originally I did them at tickover, around 1k and all was good. Having played around I noticed that the vacuum changes as you rev the bike, at 3kish the two center carbs have a higher value than the two outers.

I'm interested in peoples opinions on where you should actually set the carbs so that they synchronise. Personally I think 5k is about right since that is where you ride the bike for a fair bit of the time. Does it make that much difference? The cbr is notorious for vibrations through the bars so it makes sense to me.

[yen_powell]

It's only at tickover and just above that they need to be synchronised.
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[Ichy]

why?


Its not always true, one I can think of straight away is the XV virago. You are supposed to synch the carbs at tickover and at 3k.

[Kickstart]

Hi

Not sure there is any point to trying to balance them at higher rpm. On bike carbs the syncing just adjusts the throttle plates to each other, and with any reasonable amount of throttle the difference the adjusters will make will be nominal incomparison.

Added to which to hold 5k without any load takes virtually no throttle at all, while 5k in real riding would likely to a significient amount of throttle (and how much would depend on the load, gear, etc).

All the best

Keith
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[lonner]

on most bikes its around 1100 1200 rpm but this little srad 600 ive just got is set at 1750 to get it right.

with most bikes you must block off the pair valves which im sure you did if fitted

but as said synchronizing carbs throttle boddies etc is only relevant at low rpm with the butterflies in the closed position


once the revs have risen its down to mixture and the needle valve operation to give you smooth running.

[Ichy]

I removed the pair valves completely. ZZR, makes complete sense since the inner carbs have a different jet to the outer, probably the reason for the difference in the vacuum.

[lonner]