Carb Sync.. ? - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
 
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post #1 of 6 (permalink) Old 10-15-2014, 12:54 PM Thread Starter
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Carb Sync.. ?

I noticed today while syncing the carbs on my bike.. it sounded better when i did it by ear.

2002 vstar 650 classic

Having some MPG issues and whatnot, started the bike warmed it up and drove it for a bit. I came back and while it was running (since i planned on syncing anyways), just to use a screwdriver and see if it made any noticeable difference. I turned the screw 1/2 turn left and it didnt sound better. I turned it back to where it was, then 1/2 turn the other way... ill be damned. Sounded great, rpms increased, flawless throttle response.

The only problem was than when i hooked up my homemade manometer, it was not synced at 1/2 turn, but more like .10 turn from where i last synced the carbs.

Anyone explain this?
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post #2 of 6 (permalink) Old 10-15-2014, 02:26 PM
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What I do when I sync my carbs is to bring it in sync at idle then I rev up to around 2000 rpm and check it again at that setting. I usually have to fine tune the sync a bit more but after that it rides gooood .

2009 Stratoliner S

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post #3 of 6 (permalink) Old 10-15-2014, 04:03 PM Thread Starter
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Quote:
Originally Posted by Corsair View Post
What I do when I sync my carbs is to bring it in sync at idle then I rev up to around 2000 rpm and check it again at that setting. I usually have to fine tune the sync a bit more but after that it rides gooood .
Might have to try that as well. I did notice that when revving the engine a bit between the manometer would fluctuate a an inch or so and if i held it, the rear cylinder would pull more fluid towards it.
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post #4 of 6 (permalink) Old 10-16-2014, 09:32 AM
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Quote:
Originally Posted by Wyovstar View Post
I noticed today while syncing the carbs on my bike.. it sounded better when i did it by ear.

2002 vstar 650 classic

Having some MPG issues and whatnot, started the bike warmed it up and drove it for a bit. I came back and while it was running (since i planned on syncing anyways), just to use a screwdriver and see if it made any noticeable difference. I turned the screw 1/2 turn left and it didnt sound better. I turned it back to where it was, then 1/2 turn the other way... ill be damned. Sounded great, rpms increased, flawless throttle response.

The only problem was than when i hooked up my homemade manometer, it was not synced at 1/2 turn, but more like .10 turn from where i last synced the carbs.

Anyone explain this?
One article I read about carb syncing said rpm will decrease when the carbs are properly synced.

However, I just did a quick carb sync. I only needed a tiny nudge on the screw to get them perfect. But it did seem to audibly increase rpms when I made the nudge. I also had a tach attached (of course it fluctuates), but it started reading higher.

I thing I have absolutely verified. I can let the bike idle for 6-7 minutes and get the needles perfect. Then if I ride 3 miles and do it again, it will be off some. Idling for several minutes is no substitute for riding a few minutes.

There may be multiple factors that would cause the idle speed to increase or decrease.

Last edited by Kyle76; 10-16-2014 at 01:41 PM.
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post #5 of 6 (permalink) Old 10-16-2014, 12:09 PM Thread Starter
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Im wondering if it has something to do with the a/f ratio in a particular cylinder. I have adjusted PMS screws to compensate for the slip on exhaust that i have, and if i start the bike on choke, the rear cylinder chugs out some smoke. Nothing major, just excessively rich... i dunno... pulling at strings here
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post #6 of 6 (permalink) Old 10-16-2014, 12:29 PM
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I'm by no means an expert but I would think when everything is synced correctly the RPMs would naturally increase. Think about it...everything is getting even & smooth amounts of air & fuel. Just seems to me to be only natural to expect a small increase.

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