Carb Syncing

[muggzy]

Hey All,

 

I sync my carbs by looking down my carb throats and making sure that the slides bottom out at exactly the same time. Then I watch the slides as I slowly squeeze the thottle to ensure that they open exactly evenly and finish at exactly the same point. I've found this to be way more accurate than using the port holes on the carb bodies (which by the way always confirm my method).

 

Is there a reason they'd need to be differently balanced in order to compensate for other imbalances elsewhere in the engine? I guess I'm wondering why people find it necessary to using a "synchronizing tool" like the one that's been available through this site?

[SAVAGE420]

Ive never used the tool, always done it by eye even on triples.

 

Always works for me and others.

 

If i had one, i would try it out though just to see.

[GrMeyer]

I thought the same thing. Then I got the tool and was impressed how much I was really off.

[muggzy]

I thought the same thing. Then I got the tool and was impressed how much I was really off.

 

Hey Gr,

I'm really curious, can you see a difference in the slides when you look down the carb throats after syncing with the tool? I'd find it hard to believe that the slides are THAT sensitive that you'd notice little or know difference (we'd be talking a c-hair here).

 

If you can notice a difference, then it would seem to me that they're compensating for some inconsistency somewhere else in the engine?

 

I'm not trying to be critical at all, just trying to understand.

 

George

[muggzy]

Hey Gr,

I'm really curious, can you see a difference in the slides when you look down the carb throats after syncing with the tool? I'd find it hard to believe that the slides are THAT sensitive that you'd notice little or know difference (we'd be talking a c-hair here).

 

If you can notice a difference, then it would seem to me that they're compensating for some inconsistency somewhere else in the engine?

 

I'm not trying to be critical at all, just trying to understand.

 

George

 

I just sent a PM to F.A.S.T. who sells a sync tool.

 

Hey, I started a thread about carb syncing with a tool;

We'd love to get your input. Especially helpful might be, what is the parameter that this tool is measuring?

 

Hopefully we'll get some good input from them

[DallasGDub]

I thought the same thing. Then I got the tool and was impressed how much I was really off.

I did this as well. I thought it ran ok and seemed spot on by eye. checked it with the tool, and it was off. Ran even better after the tool.

[muggzy]

I did this as well. I thought it ran ok and seemed spot on by eye. checked it with the tool, and it was off. Ran even better after the tool.

 

OK, so a couple of you say it helped but did you look at the carb slides before and after you adjusted? was there a noticable difference? What is the tool actually measuring. If it's compensating for some imbalance somewhere else, it may be masking another problem. I'd just like to know more about it.

[DallasGDub]

I did not notice a big difference in the slide adjustment. Not by eye anyways. It is was just slight adjustments in the mid for me. It is more of a fine tunning than anything.

 

It is measuring vacuum.

 

For example: After doing it by eye, the bike ran fine. I got the tool and checked it like they do on youtube. I could hold the gas at 1/4 throttle, according to the dial on the tester, I was pulling a 5 on one side, and a 8 on the other. I have no idea what the numbers mean, or what was a good number. So I made both sides match at 7..... LOL... no joke. I fig if I was off I would notice. It did not come with instructions or anything. Anyhow, I did the idle the same way. I was not off by much, but I did noticed a difference throughout the low and mid. Not huge, just seemed to run cleaner.

 

I can see how it may mask a problem. But I think if you have a air leak or something, you will see other signs rather than being out of sync. If one slide is way up, and the other way down, and the meter says you are in-sync, I would trouble shoot something else.

Edited August 4, 2010 by DallasGDub

[crazycanuck]

I did not notice a big difference in the slide adjustment. Not by eye anyways. It is was just slight adjustments in the mid for me. It is more of a fine tunning than anything.

 

It is measuring vacuum.

 

For example: After doing it by eye, the bike ran fine. I got the tool and checked it like they do on youtube. I could hold the gas at 1/4 throttle, according to the dial on the tester, I was pulling a 5 on one side, and a 8 on the other. I have no idea what the numbers mean, or what was a good number. So I made both sides match at 7..... LOL... no joke. I fig if I was off I would notice. It did not come with instructions or anything. Anyhow, I did the idle the same way. I was not off by much, but I did noticed a difference throughout the low and mid. Not huge, just seemed to run cleaner.

 

I can see how it may mask a problem. But I think if you have a air leak or something, you will see other signs rather than being out of sync. If one slide is way up, and the other way down, and the meter says you are in-sync, I would trouble shoot something else.

 

 

There isnt a specific number to look for.... only that both carbs are pulling the same amount of air.

[wfobasheeboy]

I thought the same thing. Then I got the tool and was impressed how much I was really off.

 

 

Above X2

I got my tool from F.A.S.T. Jeff ran me through it on the phone. Really cleaned up the way the shee runs.

[TeamRealtreeHD]

I always look at the slides first, then I'll use the tool. The tool is the real deal.

[CarvedArt]

You can get it close enough by using your calibrated eye to run good enough for everyday fun. You can use your hand also, lightly place a finger on each of the slides and press the throttle then feel the drag, you should feel the slides lift at the same time. The deal with the sync tool is that it measures vacuum, where your eye measures nothing. It's like cutting a piece of paper into a square, can you get the paper to be square without a ruler? Of course; will it be a perfect square? Your chances are pretty slim. Could you cut a perfect square with a ruler by measuring each side? Your chances are far greater. It's just something to help you get your carbs closer to perfect sync; your carbs could be synced within several hundred-thousandths doing it by eye vs. maybe a few thousandths or less by using the sync tool. Will you achieve a higher horsepower by using the sync tool vs. your eye? Definitely, your essentially making more efficient use of the available fuel being delivered by the carbs. One carb will be leaner (like by about one gnats butt or so) and flow more volume than the other. Will it blow your motor? Highly doubtful. Will it be noticeable? It all depends on how far off your calibrated eye is. If drags are your gig, where every tenth counts, I wouldn't go without the tool; if riding for fun is where you're at, I'd say as long as your darn close, your close enough.

 

I almost forgot, you can also use a couple of drill bits to sync your carbs. Just get two bits that are the same size and their diameters are taller than the current openings, at the base of the slides, at zero throttle. Insert the backs into the carbs lifting the slides, increase the throttle position until the throttle is above the idle settings and just rest on the bits. (Keep the throttle pulled.) Even-up the cable slack and work the bits like feeler gauges, each one should have the same "pull" force. When they "feel" good you should be synced.

Edited August 6, 2010 by CarvedArt

[muggzy]

You can get it close enough by using your calibrated eye to run good enough for everyday fun. You can use your hand also, lightly place a finger on each of the slides and press the throttle then feel the drag, you should feel the slides lift at the same time. The deal with the sync tool is that it measures vacuum, where your eye measures nothing. It's like cutting a piece of paper into a square, can you get the paper to be square without a ruler? Of course; will it be a perfect square? Your chances are pretty slim. Could you cut a perfect square with a ruler by measuring each side? Your chances are far greater. It's just something to help you get your carbs closer to perfect sync; your carbs could be synced within several hundred-thousandths doing it by eye vs. maybe a few thousandths or less by using the sync tool. Will you achieve a higher horsepower by using the sync tool vs. your eye? Definitely, your essentially making more efficient use of the available fuel being delivered by the carbs. One carb will be leaner (like by about one gnats butt or so) and flow more volume than the other. Will it blow your motor? Highly doubtful. Will it be noticeable? It all depends on how far off your calibrated eye is. If drags are your gig, where every tenth counts, I wouldn't go without the tool; if riding for fun is where you're at, I'd say as long as your darn close, your close enough.

 

I almost forgot, you can also use a couple of drill bits to sync your carbs. Just get two bits that are the same size and their diameters are taller than the current openings, at the base of the slides, at zero throttle. Insert the backs into the carbs lifting the slides, increase the throttle position until the throttle is above the idle settings and just rest on the bits. (Keep the throttle pulled.) Even-up the cable slack and work the bits like feeler gauges, each one should have the same "pull" force. When they "feel" good you should be synced.

 

Hey carvedart, Great info as always. Thanks for the reply.

[FASTOYS]

The tool measures vacume/air velocity being pulled through the carbs. I have had some people tell me there is NO way their carbs are off as they spent hours tweaking them by eye and calipers etc.. Then they were totally shocked how far off they really were when they tried it with the Sync tool. lol

Will it help HP? Maybe not but it usually helps response of idle and bottom end. They are on sale this month too.

Click: http://bansheehq.com/forums/index.php?showtopic=133793

[dajogejr]

Keeping in mind this...as well.

Ever have an issue with one cylinder getting hotter than the other?

Idle rough, start rough, etc.?

This tool can help that as well.

 

Not only can you use it for idle, but you can also use it to make sure the cable is pulling each slide up at the same time.

Idle is controlled by the idle screw. The pull/sync is controlled by the carb top caps.

 

I set idle first, then I pull the throttle 1/4 way or so and check each carb.

 

Now...that being said, in comparison to a duner/trail rider, it is much more critical for them than a drag race guy.

 

A drag racers blips the throttle a few times and holds it WOT till the end. As long as both carb opens all the way, you're good.

 

But for the duner trail crowd, you'd be surprised how off you can be by eye. This tool is the shiznit....