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Low vacuum readings in carb sync
- vach
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I have not done a compression check, I need a gauge..
Post edited by: vach, at: 2007/06/10 22:36
1979 kz650 B. Chicago, Illinois
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- wireman
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its been a while since ive synced a set of carbs but from my personal experiance in refrigiration work 28" is a perfect vacuam and your numbers are much lower. would check your carb boots and clamps for vacuam leaks,then i would run a compression test and check your valve clearances to make sure something isnt hanging open.if its not smoking/burning oil id lean towards valve adjustment before screwing with carbs too much;)Ok, working out the bugs.. I bought a 4 cylinder vacuum gauge for syncing carbs.. On #1 I got 5 inches, #2 12 inches, #3 10 inches and #4 12 inches at 950 rmps.. The gauges say's too much valve advance.. Did my chain jump? The bike seem to be running ok but maybe a bit slow from what I remember..
I have not done a compression check, I need a gauge..<br><br>Post edited by: vach, at: 2007/06/10 22:36
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- Sandy
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- Fly High,Tony
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1977 KZ1000 A-1
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- vach
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1979 kz650 B. Chicago, Illinois
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- wireman
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- vach
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1979 kz650 B. Chicago, Illinois
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- BSKZ650
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77 kz650, owned for over 25 years
77 ltd1000, current rider
76 kz900, just waiting
73 z1,, gonna restore this one
piglet, leggero harley davidson
SR, Ride captian, S.E.Texas Patriot Guard Riders.. AKA KawaBob
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- Snakebyte
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Ok, working out the bugs.. I bought a 4 cylinder vacuum gauge for syncing carbs.. On #1 I got 5 inches, #2 12 inches, #3 10 inches and #4 12 inches at 950 rmps.. The gauges say's too much valve advance.. Did my chain jump? The bike seem to be running ok but maybe a bit slow from what I remember..
I have not done a compression check, I need a gauge..<br><br>Post edited by: vach, at: 2007/06/10 22:36
Lower vacume in the one can be the the throttle blade is open more in that cylinder causing that one cylinder to force the engine to run at higher rpm till the other cylinders pull it down to slower speed.
If your cam time was off or bent valves I dought it would run without missing or even idle at that.
Im not sure what the vacume should be on a bike, but on cars its 28" vacume. It might be lower on a bike.
I have round slides on my bike, the way I synced my carb is with a drill bit. It runs and idles perfect now.
I have synced carb on blade type carbs with no problems by looking through the carb with a light on the other side a see how much light shines through at closed throttle.
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- The Milkman
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The readings you have show that #2 and #4 are open the same, #3 it open just a tad further and #1 is open even more. Adjust #3 down a little so the reading matches 2 and 4, readjust the idle, the readings will all change some. Then adjust #1 down until it matches the other 3.
Ride safe.
Post edited by: The Milkman, at: 2007/06/11 08:33
78 650-C2, Stock engine, Jardine 4-2 Exh., 17-38 sprockets, dyna ignition and coils, coil wiring mod, carb mod.
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- vach
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1979 kz650 B. Chicago, Illinois
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- tjettim
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even if I have to idle it up some.Some after
market cams will lower your vacuum because of
the overlap.If your compression is good and
the exhaust note sounds normal ( a cam off a
whole tooth usually makes the bike sound totally
different),I would just set all the carbs the same
and see how it runs.
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- vach
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Post edited by: vach, at: 2007/06/11 12:28
1979 kz650 B. Chicago, Illinois
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