Topic: Where are the @&#/$ing sync screws? :)

[JoeP]

I fired up my cb550 yesterday for the first time after the rebuild and it roared to life without a stumble-- happy! Now I'm trying to check that the carbs are synced but don't know where the sync adjusters are. Are they the three screws between the 4 carbs near the bowls, or are they the four screws beside each carb up near the top covers? I've looked but can't find anything. Thanks!

[JoeP]

75 cb550f. I think they are the stock carbs. They say Keilin on them.

[Deltarider]

or are they the four screws beside each carb up near the top covers?

They probably are if you have the old style Keihin carbs (069A or 022A or 087A). The 550F has the 069A.
Do you have the Honda Shop Manual 500/550? The setting screws are shown on p.8 in fig.7.
Can't believe you did a rebuild and you do not know... never mind.
I advise to do all the checks and timings well before you start syncing. Especially the ignition should be checked and doublechecked (all aspects).

[JoeP]

or are they the four screws beside each carb up near the top covers?

They probably are if you have the old style Keihin carbs (069A or 022A or 087A). The 550F has the 069A.
Do you have the Honda Shop Manual 500/550? The setting screws are shown on p.8 in fig.7.
Can't believe you did a rebuild and you do not know... never mind.
I advise to do all the checks and timings well before you start syncing. Especially the ignition should be checked and doublechecked (all aspects).

My manual seems to be missing that page. I bench synced them using the 4 screws near the top covers, but i was thinking the three screws near the bowls would be better for syncing relative to each other from the way the linkage looks. Btw I'm using a twin syncer so I can only sync two at a time.

Ignition timing, valves have already been set. Bike has great throttle response off idle.

[dave500]

your best with four gauges or you may end up chasing your tail to get a good final balance?

[Deltarider]

For some reason this site likes to transfer corrupted data. The complete Honda Shop Manual 500 - 550 is found here: http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual
And page 8. is in part 1: http://www.honda4fun.com/pdf_man_officina/pdf_manuali/CB500-550/CB500-550-K_01.pdf

[JoeP]

For some reason this site likes to transfer corrupted data. The complete Honda Shop Manual 500 - 550 is found here: http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual
And page 8. is in part 1: http://www.honda4fun.com/pdf_man_officina/pdf_manuali/CB500-550/CB500-550-K_01.pdf

Thanks!

[lucky]

How can you work on carbs and not even know what the screws are for?

When you "SYNC" carbs what you are doing is setting the idle in each carb when the throttle is closed by adjusting the height of the carb slide. .007 thousandths of an inch will make a difference.


Do not turn the mixture screws when syncing the carbs. Leave them alone.

[JoeP]

How can you work on carbs and not even know what the screws are for?

I saw two different sets of screws that looked like they could perform the same function. Just wondering which set people usually use. And I was missing the manual page until Deltarider posted the link.

[JoeP]

Just an update. I was able to sync my carbs using the 4 screws near the top covers (just like the manual said, wow). The three screws near the bowls didn't have much of an effect when trying to sync.

I used a Carbmate (twin) with a 4 carb adaptor. Even with the adaptor, the device can only sync two carbs at a time so I made up a process that wouldn't have me chasing my tail. For those that are interested in using this device, here it is. The adaptor has 4 hoses which I'll call left to right 1,2,3,4. The process was:

1) warm up the engine and shut it off
2) hook up carb 1 to hose 2, carb 2 to hose 1, carb 3 to hose 3, carb 4 to hose 4.
3) start the engine
4) open hoses 1 and 2 and use the screw on carb 1 to sync. Close hoses 1 and 2.
5) open hoses 1 and 3 and use the screw on carb 3 to sync. Close hoses 1 and 3.
6) open hoses 3 and 4 and use the screw on carb 4 to sync.

That's it. I got all 4 carbs synced to within 0.5 cm/HG, which is better than the tolerance specified in the manual. Not as easy as using 4 vacuum gauges, but I had to work with what I had and it took less than 10 minutes. Thanks all.