Syncing carbs.

Good afternoon, all!

My father and I syned my carbs yesterday, but on cylinders 1 and 4 adjustments did not change the way the bike ran at all. No noticeable mercury movement or running condition- 2 and 3 made massive differences. What I find interesting, however, is the fact that all are sucking air. Could this be something with the air needles at the back of the carbs?

Also, the bike is VERY slow returning to idle. I see the butterfly return instantly when I let go of the throttle and I cannot seem to locate any leaks.

On a side note- should I have the holes on top of the carbs (2) covered with vacuum plugs? I did not, but now I do- it did not change the way it runs either.

The RPM soaring is a new development. Thanks for any help!

Oh, does anyone have a '77 KZ650 factory airbox they don't want? Thanks!

I've read through your various posts and you're making good progress.

Before you go to the carbs again check your valve clearances first. It appears you've done the other tune-up procedures.

The two holes on top of the carbs are vents, don't plug them. Instead attach hoses and run them up to the airbox area, or better yet, let them fall back over the carbs and hang behind the engine, over the swingarm.

I'm not sure but did you clean the carbs? If so then did you perform a bench sync? It's different from a mercury sync.

What condition are the intake manifolds? If they are cracked then air leaks can happen and cause a varied idle and slow return.

Another thing is to double check the throttle cables; make sure they are clean inside and slippery, and they should be routed so there are no sharp bends from the throttle to the carb bank. A sharp bend can hang up the action and mess with the idle.

Thanks for the info! I will check these things out! No, I did not do a bench sync. I did, however, take them apart and cleaned them out really well. No plugs, the floats move easily, etc. I am running cones so I know the engine is sucking in too much air causing me the need to up my jets, but it still should run okay at higher speeds. It's hard to find someone to work on a cruiser anymore so I am having to learn as I go with a lot of the carb stuff. Have a great night!

There is a VM Carb Connections link under "wg's Tech Stuff Index" on our website that should help you hook the carbs up.

What did you have the vacuum gauges hooked up to? If there was no change in vacuum reading and you did have the mercury up in the gauge:

1. slides not moving
2. gauge not hooked up to the vacuum fittings correctly

Can think of no other alternatives.

I can't think how two slides would move and not the other two unless bolts that hold slide mechanisms to slide rod are not in place... gauge's vacuum lines should be connected to vacuum ports on carb holders.

You mention "butterfly" in your first post, and I assumed you meant "slide". Your bike came stock with carbs that used slides.

Do your carbs really have "butterflies", which are flaps that rotate on a shaft? If they do then you have something different....

Because of its shape, some folks call the bell crank a butterfly.