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Dumb carb synch question

  • Thread starter Thread starter MisterCinders
  • Start date Start date
M

MisterCinders

Guest
Getting ready to finish up my carb job. I bench synched the carbs and have the vacuum tool for a real synch job.

After reading the various guides and Clymer's I have a really basic question.

Once you have the synch tool hooked up, it looks like you measure and adjust the throttles while the engine is running. Is that right?

To change the throttle slides on my bike, I have to remove the carb tops to access the lock nuts and screws for the slides. Do I really open up the carb tops with the engine running? Won't that spray fuel/air mixture everywhere?

Or do I measure the vacuum, shut off the engine, open and adjust throttle slide, close it up, restart engine and check the new level? That seems terribly cumbersome, but does not have open carbs with a running engine.

Of course, I am pretty dumb so . . .
 
Nope you can run the bike with the tops off. Really just dust covers.
 
The slides will hold all the air/fuel mix in there, no spray

Did you get the combination screwdriver/wrench? If not, be sure and do the adjustments carefully

Don't forget:

1. Set up a fan, blowing at the front of the motor
2, Plug off the vacuum port line. Golf tee or allen wrnch works fine

So, fire it up and adjust away. Just don't let it get too hot. Since it's your first time, you'll find it can be frustrating to learn.
 
Take a short ride to warm things up. Shut the engine off. Remove the gas tank and the carburetor tops, then loosen all the locknuts. Hook up your vacuum tool. Plug the vacuum line that goes to the petcock. Start the engine, tweak the screws until they are close. Perfection is not required. The book says to do the adjustment at something like 1,700 RPM, that's one way to do it. Whichever cylinder is the farthest off the others, do it first, then go to the next, and the next. You want to gently herd them all together, not set them to any particular place. I like to get them as close as I can at several ranges of RPM, idle, 1000 or so, maybe around 2000. Just tweak them until they stay close at all of these ranges. Just pull the throttle gently to raise or lower RPM. If you can't really get them perfect at more than one RPM, don't bother trying. Anything close will run fine, just do as good as you can. Ten minutes spent chasing the adjustments won't get it any more synchronized than you can do in the first minute.
The whole thing should take about a minute or two. You don't need a fan, a minute or two idling won't hurt anything. If it is taking too long (perfectionist) and you are worried about heating up the engine, shut it off and drink a cup of coffee or something. Once you get it as good as it's going to get, shut it off.
Set the locknuts without letting the screws turn, start it up and try it again. If they are still close enough, shut it off and install the top covers, then go right into the highest idle air screw adjustment.

The fan idea must be for those tuning CV carbs and taking a half hour to do it, on a hot day in the summertime in Phoenix. With these VM carbs it literally takes only a couple minutes to do the whole thing.
 
Takes longer to get ready to sync than to do the job. Actual Sync should take like 5 minutes at most. Having the carb tool makes it a snap.. Just make sure to plug the vacuum line or you will be chasing the adjustment all over the place
 
Where can I find this magical carb tool? It sounds pretty sexy.

Searched Z1, but did not find one.
 
I have a synch tool. Others have described a combination hex bit/flat screw driver tool for adjusting the throttle slides and lock nuts. This tool I cannot locate.
 
MisterCinders said:
Where can I find this magical carb tool? It sounds pretty sexy.

Searched Z1, but did not find one.
Click to expand...
With Z1, you really need to call and talk to Rob. They have lots of stuff that is not on the web site, and they will also order stuff for you and ship it. For example, I just received a set of valves for my GPz. Rob went out of his way to find them for me, and at a reasonable price to boot. Give them a call.
 
Thanks koolaid. I am definitely a Z1 fan. Every order from them has come in super fast, and they are great on price.

Some other vendors, by contrast . . . .
 
MisterCinders said:
Thanks koolaid. I am definitely a Z1 fan. Every order from them has come in super fast, and they are great on price.

Some other vendors, by contrast . . . .
Click to expand...
Certainly. Years ago, when I had my 81 KZ750E, I needed a clutch cable. Jeff sent me a Motion Pro, which did not fit and was clearly of inferior quality. I called him and talked to Jeff. He ended up ordering an OEM cable from Japan for me. Just unreal service and fantastic support.
 
Hi,

For what it's worth, Mr. bwringer and I both have carb sync guides on our respective websites. They are for CV carbs but should give you an idea of the procedure.


Thank you for your indulgence,

BassCliff
 
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