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First Carb Sync - does this look OK?

Old 05-13-2008, 07:15 PM
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First Carb Sync - does this look OK?

After removing and installing the carbs a half dozen times to get the jetting in I was expecting a lot more unbalance than this. This is only the second time I've tried to sync carbs in a lot of year of riding. I spliced in and added tubes per Gregs site and I'm pretty damn sure everything was sealed well because if I removed the caps while running the idle increased. Am I kidding myself here? Is this really not that good? It seemed to make no difference if I capped off the two extra tubes on the Motion Pro unit.

At idle:

100_0717.jpg?t=1210731285

at 3500 RPM:

100_0718.jpg?t=1210731327
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Old 05-13-2008, 07:31 PM
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I can usually get it a "tad" closer at idle but I've never heard or done a 3500 reading. What's that all about?
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Old 05-13-2008, 07:40 PM
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Personally i would try to get them closer at idle and 3500 rpm. I don't use the mercury style gauges thou.

I have a bank of four dial gauges and just connect each gauge one at a time to calibrate it off of the same carb, then i connect up to both carbs via my perminently re-directed hose connections and and turn the single screw as needed.
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Old 05-13-2008, 08:26 PM
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Assuming the numerals are inches and the liquid is mercury, it looks like you've got them within spec, but just barely. I use ATF in my homemade sync gauge and usually get the columns within a half inch of each other, but that is equivalent to like a sixteenth of an inch of mercury. At least on my VTR, getting them REALLY close makes the bike run noticeably better.

Last edited by RK1; 05-13-2008 at 08:30 PM.
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Old 05-14-2008, 05:58 AM
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I'll do some more tweaking but won't it make one or the other worse? It's high on the right at idle and high on the left at 3500.

Yes, it's mercury.

I'd rather have them syn'd at 3000-4000 rpm because I don't normally spend most of my time at idle.

Thanks folks.
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Old 05-14-2008, 10:07 AM
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I've only ever adjusted them at idle. When I get them really close, it runs good everywhere. I never checked at higher rpm so don't know what to tell you.
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Old 05-14-2008, 10:17 AM
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Your pretty close... I found the balance between will change some as your RPM changes... so I just dial them in as close as possible on idle, and have been pretty happy.

J.
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Old 05-14-2008, 10:21 AM
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If you get them dead on at idle they will be equal at 2500 rpm too... never failed yet for me...
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Old 05-14-2008, 06:38 PM
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Is that a large column of water on the right tube above the mercury?
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Old 05-14-2008, 06:57 PM
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The farther you open the throttle the less cab sync comes into play because you are adjusting the slide heighth starting point which effects idle a lot. It looks OK; if a road test show good driveability your are done.
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Old 05-14-2008, 07:07 PM
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Originally Posted by Tweety View Post
If you get them dead on at idle they will be equal at 2500 rpm too... never failed yet for me...
Yer a Fart Smucker

Worked out the same way for me.


Greg, it very may well be water but I'm not 100% sure as it's a borrowed manometer. You're probably going to tell me that what I've done is garbage now because of water in the unit huh?

I'll head back out there and see whats up.


Yea, it appeared to be some water. I looked at it closely off the bike and saw a line. I gently blew in to the hose and it went in to the reservoir. Now it looks like there may be a little water floating above the mercury in the reservoir.

I'll do it again after I get the wheels back on. I assume as long as the waters on top and I'm only drawing mercury the next time I'll be OK.

Good eye!

Last edited by Involute; 05-14-2008 at 07:18 PM.
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