Carb Sync Issues

[RichCumming]

Having a problem getting the carbs to sync.
I can get 1 & 2 synced, and 3 & 4 synced but I cannot get all 4 together.
1 & 2 are pulling high vacuum and 3 & 4 are low.
If I rev it up 1 & 2 go off the scale and 3 & 4 hardly move!

Where am i going wrong?

[Kreylyn]

Having a problem getting the carbs to sync.
I can get 1 & 2 synced, and 3 & 4 synced but I cannot get all 4 together.
1 & 2 are pulling high vacuum and 3 & 4 are low.
If I rev it up 1 & 2 go off the scale and 3 & 4 hardly move!

Where am i going wrong?

What bike?

Checked the valve clearances? Carbs rebuit? Why are you at the point of syncing them? What tool are you using, and how are you going about doing the sync?

Krey

[RichCumming]

The bike is a 94 GSX600F.
I only got the bike a few weeks ago so I was giving it a service and wanted to check the balance as the idle was uneven.
I have a 4 line vacuum gauge
When I first checked it 1,2 and 3 were even but 4 was off. I adjusted it to get them all even but the idle speed went up to 3500 with no way of adjusting it down.
I played with the adjusters and have now got the idle down but as I stated the balance between carbs is way off.
I adjusted 1 & 2 first then 3 & 4 but when I adjust the center screw between 2 & 3 the idle goes up again

[Kreylyn]

The bike is a 94 GSX600F.
I only got the bike a few weeks ago so I was giving it a service and wanted to check the balance as the idle was uneven.
I have a 4 line vacuum gauge
When I first checked it 1,2 and 3 were even but 4 was off. I adjusted it to get them all even but the idle speed went up to 3500 with no way of adjusting it down.
I played with the adjusters and have now got the idle down but as I stated the balance between carbs is way off.
I adjusted 1 & 2 first then 3 & 4 but when I adjust the center screw between 2 & 3 the idle goes up again

Idle going up generally = you getting the bike closer to proper sync and running right.

As you sync, you adjust the idle adjustment cable to bring the rpms back down. If it is hanging high rpms somewhere and staying there even with adjusting the idle cable, something else is binding up the throttle and keeping it open or you have fuel from another source (not the pilot jets) making it rev high. Disconnect the throttle cables for example, or check that your choke plungers are actually fully closed.

Oh, and make sure all of your vacuum ports are closed off like the petcock vacuum line/port.

Krey

[RichCumming]

Krey

I checked all the throttle cable linkage etc and the throttle is not getting bound up anywhere. The linkage is not even touching the idle adjustment screw. The choke plungers are all closed.
I did not close out all the vacuum lines so I will see if that makes a difference when I get back to it tomorrow.

Richard

[gwigs]

Sync them up visually first,you have to do it with the carbs off.All you do is adjust the screws so that the butterflies are all pretty close.If you open the butterflies you will see a couple of small holes in the carb body.Adjust so each butterfly is just showing first hole.Chuck the carbs back on and you should be close enough to sync with gauges easily... sync at 1750 rpm...keeep adjusting to 1750rpm till you have them syncd...thats it,then just set idle speed and youre done..

[MikeyZ]

Idle going up is going to happen. Sync 1 and 2, then 3 and 4. Then sync the pairs together. When you do this, the idle WILL rise. Once they are all 4 synced you turn the idle down with the idle screw.

Easy easy

[05RedKat600]

Krey

I checked all the throttle cable linkage etc and the throttle is not getting bound up anywhere. The linkage is not even touching the idle adjustment screw. The choke plungers are all closed.
I did not close out all the vacuum lines so I will see if that makes a difference when I get back to it tomorrow.

Richard

This right here should stop your high idle issue. If it doesn't, you've probably got a crack in a boot or other vacuum leak.

[Wild-Bill]

...The linkage is not even touching the idle adjustment screw...

THAT would be a problem. Sounds like you need to adjust the throttle cable to introduce some slack.

Just to eliminate the possibility, try connecting each vacuum line to the same carb to make sure you're getting the same reading.

[RichCumming]

Thanks for all the advice. Very much appreciated
Carbs are now all happily in sync with one another.
I took the carb off, striped them down and cleaned everything out then blew out all the lines.
I found that all the air/fuel mixture screws were set differently to one another so I matched them all up at 2 1/2 turns out.
I then set all the butterflies but putting a 1/16th drill bit in carb 1 and adjusting all the others to match using a second 1/16th bit.
Put everything back together carefully making sure that everything was seated properly and not leaks were present.
Put the vacuum gage on and made some very slight adjustments and everything is now running perfectly!

[gwigs]

Awesome, glad you have it sorted..

[Wild-Bill]

Good to hear a success story!