Carb. Synch. Question, did it for the first time today - Sportbikes.net
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post #1 of 13 (permalink) Old 03-10-2007, 09:11 PM Thread Starter
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Carb. Synch. Question, did it for the first time today

Hi,

I got a carb synch tool today, and decided to give it a crack. Turns out, it is pretty easy, but I've got some questions I can't quite figure out, even with the Haynes and Clymer manual.

For some reason, cylinder 2 was the only one with no vacuum hose, just a screw plug. So, I continued on anyway, and found the other three all out of whack, to which I then wondered, "Well, which one should I set the other ones to?" I decided to set the three of them (didn't have a fitting for cyl. 2) to the 4th carb (rider's perspective) and I remember reading somewhere once the 4th carb is the "base" carb?)), put everything back together, and it does seem to run noticably smoother, but it sort of bothers me that I skipped #2. Then again, I only took it for a test ride around the block. I suppose I'll get the fitting for it, and do it again, but I figured I'd ask here to see if there's some reason #2 has a plug, maybe that one is somehow permanently set??? I , don't have enough experience working on carbs....!

Thanks!
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post #2 of 13 (permalink) Old 03-10-2007, 11:34 PM
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mmm different manufacturers do have different setups. And yes one of the carbs is usually designated as the reference carb, and may be different to adjust. But I believe all should have a vacuum nipple, otherwise how can you refer to it. I'm sure you can buy a threaded insert nipple to read that carb.
You really should invest the $20 or so in a shop manual, or check out your local library. For now, just pop into your friendly dealer...he'll hook you, for a small fee of course!
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post #3 of 13 (permalink) Old 03-11-2007, 07:38 AM
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Can you swap the screw plug for a nipple from one of the other carbs and sync it that way? Just guessing, that's the last bit of winter maintenance I have yet to do myself.

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post #4 of 13 (permalink) Old 03-11-2007, 10:00 AM Thread Starter
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Quote:
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Can you swap the screw plug for a nipple from one of the other carbs and sync it that way? Just guessing, that's the last bit of winter maintenance I have yet to do myself.
Friggin GREAT idea! Wish I had thought of it as I was doing it! Now that everything's back together, I'm going to get a nipple for it at the local shop before I tear everything down again... Of course, I'll also see if I can find a shop manual somewhere too, as BlueFazer05 suggests...

Even so, anyone else have that one plugged up cyl. and know why?
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post #5 of 13 (permalink) Old 03-11-2007, 01:23 PM
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Except you have to do them all together. Didn't your carb tool come with nipples?

-- Jim


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post #6 of 13 (permalink) Old 03-11-2007, 02:29 PM Thread Starter
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Quote:
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Except you have to do them all together. Didn't your carb tool come with nipples?
Yes they did, but not the right size, and bike shop was already closed...
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post #7 of 13 (permalink) Old 03-12-2007, 10:47 AM
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The way I did it, I'd sync up 3 to 4. Then 1 to 2. Then sync the pairs (3&4/1&2) together.
post #8 of 13 (permalink) Old 03-12-2007, 11:20 AM
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The number 2 carb is your base carb.

It really doesnt matter though you just want all 4 the same.

The #2 needs a nipple screwed into it and then you sync up 1&2 and then 3&4 and then you sync up the two pair.

Youll have to do it 3 or 4 times to get them perfect.

cause rascus said I had to.........
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post #9 of 13 (permalink) Old 03-12-2007, 01:31 PM Thread Starter
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Quote:
Originally Posted by hybrid
The number 2 carb is your base carb.

It really doesnt matter though you just want all 4 the same.

The #2 needs a nipple screwed into it and then you sync up 1&2 and then 3&4 and then you sync up the two pair.

Youll have to do it 3 or 4 times to get them perfect.
..ah, base carb, thanks! I did the best I could with the three, and yeah, you're right, it took several times to just get the three synched. It was kinda fun though, I sort of can't wait to get the nipple and give it another shot.

Although I will say this, I can't believe how far off the three were when I started... # 1 was off the chain, #3 barely sucking up, and #4 pretty much right in between both 1 and 4... ...and that's with maybe 6-7k miles from my last synch.
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post #10 of 13 (permalink) Old 03-12-2007, 02:00 PM
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Youll see that when you get the right nipple to do that.............the #2 carb wont change at all.

Its not set up to allow movement of the throttle plate..........therefore all the others should match it.

Sync'ing the carbs will only help with idle and off idle transition. All you are doing is making all the throttle plates sit at the same place or in an older bikes case you make them sit in the appropriate place (due to uneven wear) to make the carbs see the exact same vacuum signal.

cause rascus said I had to.........
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post #11 of 13 (permalink) Old 03-12-2007, 09:45 PM Thread Starter
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Quote:
Originally Posted by hybrid
Youll see that when you get the right nipple to do

Sync'ing the carbs will only help with idle and off idle transition. All you are doing is making all the throttle plates sit at the same place or in an older bikes case you make them sit in the appropriate place (due to uneven wear) to make the carbs see the exact same vacuum signal.
This I can believe. I was thinking about it, and wondered just how far off they can possibly be, the range is finite, but not only that, a very small proportion compared to the total travel of the throttle plates.
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post #12 of 13 (permalink) Old 03-12-2007, 11:39 PM
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You should raise the rpm to about 3000 and verify balance. Hopefully they should remain even.
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post #13 of 13 (permalink) Old 03-13-2007, 09:10 AM
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Quote:
Originally Posted by BlueFazer05
You should raise the rpm to about 3000 and verify balance. Hopefully they should remain even.
Be careful though. Many a shadetree mechanic has sucked mercury into his intake revving the bike with the sticks attached.

I like to just blip it slightly and see if the sync holds when it returns to idle.

-- Jim


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