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Questions on '83 to '93 Carb Sync

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#1: Newbie question on carb sync on '84 Venture Author: wyomech, Location: WY, Southeast Posted: Thu Aug 24, 2006 3:55 pm

I bought a 1984 Venture about 2 weeks ago and I'm really enjoying the bike.

One minor problem: at idle or slightly above 1,000 rpm, the engine would "chuff" through the exhaust. I determined that #3 cylinder (the right rear one, right?) wasn't hitting at all at idle. I did a little minor fiddling with the rearmost synch screw on the right side (where there are two screws side-by-side) and #3 picked up.

I've read the articles on carb synching, but both that I've read are for the later Ventures, not the first generation, and the illustrations/photos seem to be a bit different from what I see on my Venture. I've ordered the manual from RepairManual.com, but it hasn't arrived yet. I have a set of Motion Pro mercury carb "sticks," by the way, and I've synched carbs on Japanese transverse fours and my BMW "airhead."

Soooo, here're my questions:

1) There are two screws between the right side carbs, and one screw in the corresponding area on the left. What does each screw do?

2) Is there a separate idle-speed adjustment screw (a la my 82 Kaw or 78 Suzy)?

3) Is there a specific, optimal order in which one should adjust the synch of the carbs?

Answers and further suggestions will be greatly appreciated.

Rodger

#2: Author: Neil86, Location: Alberta, Rocky Mountain House

Posted: Thu Aug 24, 2006 5:06 pm
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okay..on the 83-93 first gen

1) hook up gauges (manometers, whatever you have), warm up engine.

2) set idle to 950-1050 rpm...you'll see a knurled screw head pointing down between the #1 & #2 carbs (riders left side), you can turn it with your fingers.

3) adjust the slotted screw between #2 & #1 carbs so the vacuum on these two carbs are equal. Readjust idle speed if required, rev engine slightly between all adjustments and return to idle to see that readings stay equal.

4) adjust the rear screw of the 2 slotted screws between the #3 & #4 carbs so that # 3 & #4 carbs draw equal vacuum. Recheck left carbs and idle...readjust as needed.

5) adjust the front screw of the 2 slotted screws between the #3 & #4 carbs so the right banks of carbs draws same vacuum as the left set of carbs. Readjust idle as required .
Unhooked vacuum gauges, install caps. Done deal.

Carb numbering
rear left #1.... front left #2..... rear right #3.... front right #4

3: Author: Tony1M, Location: Alberta, Edmonton

Posted: Fri Aug 25, 2006 3:48 pm
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This may help a bit:

You'll probably want to do a mixture pretty soon. (The road to perfection MUST be driven.) Get one of these:
http://www.carbtune.com/colortune.html

Some more info:
http://www.ldrider.ca/techpages/colortune.htm

Here's a video of a colortune in use (unfortunately, not on a bike):
http://home.comcast.net/~s1500/colortune.avi

There are many threads which discuss the use of this tool. Just do a search.

Last update: 01:22 PM Saturday, August 26, 2006

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