jumped timing? vacuum gauge very erratic, low power, top speed 70mph. - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 3 (permalink) Old 08-21-2012, 12:57 AM Thread Starter
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jumped timing? vacuum gauge very erratic, low power, top speed 70mph.

New to this site. been riding for 45 years, making repairs for almost the same time. I recently purchased a 1989 vn-750a, with 25k miles no leaks no smoke, starts with no choke, has a strange sound like a mild blow by from valve over-lap. I placed vacuum gauges on the carbs for synchronizing but the needles are jumping too wildly be read. unable to do a compression check at the moment, throttle response is slow, take off in first gear is agonizingly slow. (my last bike was a hayabusa). I have my suspicions as to what is wrong but thought maybe someone might have a good place to start to identify the problem. plugs are new, when the vacuum line on the left is removed from the carb, the bike dies immediately . when the vacuum line is removed from the right carb there is no effect. open to any and all suggestions for a cure. thanks
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post #2 of 3 (permalink) Old 08-21-2012, 01:41 AM
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When you are checking the vacuum and syncing the carbs, you need to restrict the flow from both carbs via little flow valves. They should have been included in the kit.

Vacuum should not be left open, or it will cause issues (such as the bike dying). Left vacuum goes to the petcock, as I am sure you found out, and the right goes to the emissions system. There is a procedure called coastering/marbling that gets rid of it (the right gets plugged)

Now, the noise you hear, is it a tapping sound, upper cyl? If so, probably the Automatic Cam Chain Tensioners. They begin to get weak, and can cause the cam chain to jump, affecting timing. If they're failing, switch to manual tensioners instead of replacing them.

Your issue may just be due to dirty carbs, with the other noises of the bike possibly leading you down other paths. Run a heavy dose of seafoam in your gas for a few tanks and see where you land?

Both of my bikes start without choke fairly fine, as long as its warmish out. If it's colder, it's just easier to hit the choke.

Welcome, and best of luck!

PDF Manual: http://www.tocmanufacturing.com/File...nd%20Parts.pdf

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars

1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350

Last edited by thtanner; 08-21-2012 at 02:03 PM. Reason: Spelling
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post #3 of 3 (permalink) Old 08-21-2012, 12:59 PM
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...an 89 with 25k ?...yup...the ACCT....

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