Vacuum Leaks - Seek & Find Tips - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 8 (permalink) Old 09-12-2011, 11:14 PM Thread Starter
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Vacuum Leaks - Seek & Find Tips

While working on my '85 Vulcan 750 i suspected i had a vacumm leak between the carbs and the head intakes. I remembered a trick an old car mechanic showed me years ago on how to find these leaks on a car engine or motorycycle engines.
Find one of those small portable propane bottles everyone keeps around or get one from your local hardware dealer. I usually just turn the valve on the small propane bottle and let the gas flow. NO striker or cig ligter needed. With the enigne running as close to idle as one can get it to, place the nozzle end of the propane bottle around clamped off hoses or any where you suspect there might be an intake leak. If you come upon a leak the engine rpm will increase thus telling you that this is the location of an vac leak. Hope this is helpful!
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post #2 of 8 (permalink) Old 09-13-2011, 12:20 PM
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It seems like it would work, but propane leaks make me leery. I would imagine a can of wd40 would do the same and your diagnosing would be much more pinpoint.
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post #3 of 8 (permalink) Old 09-13-2011, 06:06 PM Thread Starter
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Have used this for years and never had a problem, but, have never used WD40 to find leaks either
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post #4 of 8 (permalink) Old 09-13-2011, 07:40 PM
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wd-40 would leave a mess, propane will not!

1986 vn 750 aka "Huck Farley"
42,000 miles
Rick's stator and rr
Tuxedo stator cover mod
pickup coil mod
dampers replaced
agm m/f battery
Harley sportster exhaust, degoated
Hid conversion
splines lubed
custom "vn750.com" grill cover
NGK Iridium spark plugs


acct to mcct mod https://www.vn750.com/forum/showthread.php?t=17917

rekeying locks, https://www.vn750.com/forum/showthread.php?t=7309

stator replacement walkthrough, https://www.vn750.com/forum/showthread.php?t=11369
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post #5 of 8 (permalink) Old 09-13-2011, 08:27 PM
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you can also use brake cleaner, carb cleaner or just about any flammable spray. If you are really lucky you have access to one of those cool ass smoke machines with the dyed smoke.

I remember reading somewhere that you could use a lit cigarette too, but I don't know how comfortable I would be with that.
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post #6 of 8 (permalink) Old 09-14-2011, 04:00 AM Thread Starter
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Adding a pack of cigs would drive the cost up
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post #7 of 8 (permalink) Old 09-26-2011, 10:58 PM Thread Starter
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After taking all the carbs off and all of the factory items attached to the intake system, im pretty amazed that the carbs have enough space to breath, especially after entereing the air filters,going down two narrow bottle necks, down the air box and then down two intake tubes to the carbs, lots of turns & twists here!! I suppose thats the reason folks do the "ear shave" thingie. Just a few thoughts runnin round in a riders head here today
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post #8 of 8 (permalink) Old 09-27-2011, 12:21 AM
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Yeah the airbox (Plenum,surge tank whatever) is quite a contraption isn't it? I saw pictures of one that was for sale fully assembled off the bike. Looked like an alien body part. Then you get to the actual little square chicklet intake holes in the ears themselves and wonder how does it perform as well as it does? I guess the chamber prob has some engineering for circulation and all that but I don't regret ditching mine.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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