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Author Topic: Carb / HM300 sync question - KO  (Read 960 times)

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Offline Johnie

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Carb / HM300 sync question - KO
« on: June 18, 2008, 11:36:07 AM »
Just wondering...last fall when I got my KO that had been sitting for 17 years, I did the usual valve adjustment, new points, condensor, plugs, carb rebuild, etc.  Last I did the sync with my Morgan carbtune.  I did all this with the 4 into 2 exhaust the PO had on it.  I did not want to "blue" my new HM300's during the tuning / idle process of the carbs, etc.  So now that I have my new 4 into 4 HM300's on, will that change the carb sync settings or not usually?  And I do use a fan during the sync.
« Last Edit: June 18, 2008, 11:43:51 AM by Johnie »
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Offline Gordon

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Re: Carb / HM300 sync question - KO
« Reply #1 on: June 18, 2008, 12:59:05 PM »
Nope.  Changing pipes will have no effect on carb synchronization.
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Offline Bob Wessner

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Re: Carb / HM300 sync question - KO
« Reply #2 on: June 18, 2008, 01:27:04 PM »
Quote
And I do use a fan during the sync.

I'd recommend a fan be used anytime you are running it for more than a few minutes, which would likely include syncing carbs, but as Gordon points out, changing pipes shouldn't change the sync of the carbs.
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Offline 333

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Re: Carb / HM300 sync question - KO
« Reply #3 on: June 18, 2008, 01:36:52 PM »
I would respectively disagree.  The idea of sync is that back pressure has an affect on the carbs.  Anything that disrupts the flow of air/fuel/exhaust affects sync.  So if the left side has a slightly different back pressure than the right in a 4 into 2 system, syncing the carbs compensates.
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Offline Bob Wessner

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Re: Carb / HM300 sync question - KO
« Reply #4 on: June 18, 2008, 01:47:21 PM »
What you say does seem logical. Might be worth doing a before/after comparison of the sync.
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Offline Jonesy

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Re: Carb / HM300 sync question - KO
« Reply #5 on: June 18, 2008, 02:03:16 PM »
When I repaired the holes blown out of the upper 2 mufflers on our CB550 I had to resync the carbs afterwards. It wasn't an earth-shattering change, but it was noticable.
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Offline greenjeans

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Re: Carb / HM300 sync question - KO
« Reply #6 on: June 18, 2008, 02:22:34 PM »
Quote from: Jonesy on June 18, 2008, 02:03:16 PM
When I repaired the holes blown out of the upper 2 mufflers on our CB550 I had to resync the carbs afterwards. It wasn't an earth-shattering change, but it was noticable.

Agreed.

I just repaired some blowout holes on a couple of my pipes and had to synchronize again.  The change wasn't much, but it was noticible on my Morgan Carbtune.
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Offline Gordon

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Re: Carb / HM300 sync question - KO
« Reply #7 on: June 18, 2008, 05:02:37 PM »
Sure, if you've plugged holes in the exhaust after synchronizing the carbs then you should probably re-synch, but the question was about switching pipes from 4-2 to 4-4.  If both sets of pipes are in decent condition then you really don't need to synch, but it's not going to hurt anything if you do. 
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