Firing on one cylinder... need help. - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 16 (permalink) Old 06-24-2011, 03:18 PM Thread Starter
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Firing on one cylinder... need help.

First of all this is my first v twin motorcycle. Picked it up for $400, it was complete but has been sitting a while. First thing i did once i got it home was clean out the carbs and fuel tank. The carbs didnt look bad, but did need a cleaning. After i put everything together, it starts fine, but only runs on 1 cylinder (the back cylinder). The front has spark, and gets gas (plugs are wet), but not sure what to look at next. I would really like to get this bike running good because me and a couple buddies want to make a small road trip before the end of summer. Any help is appreciated.
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post #2 of 16 (permalink) Old 06-24-2011, 03:38 PM Thread Starter
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Heres a video of it in as is condition, it was taken with my cell phone so it sounds a little weird, i think most of the noise is the carbs...

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post #3 of 16 (permalink) Old 06-24-2011, 03:40 PM
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Well like you said you have two of the three necessary components (spark, and fuel). The last one is air.

Is there anything restricting flow in the airbox, or exhaust pipe?

Have you checked the compression in that cylinder? It won't fire if the compression is too low.

Is there a good spark on both plugs?

Here's a good troubleshooting list.
4-Stroke Trouble Shooting

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post #4 of 16 (permalink) Old 06-24-2011, 03:57 PM Thread Starter
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Spark plugs are new, haven't tested compression as i don't have a tester, nothing seems to be restricting air flow either way, ill see if i can find a compression tester to borrow.
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post #5 of 16 (permalink) Old 06-24-2011, 04:16 PM Thread Starter
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Just for the hell of it, i went outside and started it up and put my hand in front of the carb for the front cylinder, and there is no suction.... what could cause this?
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post #6 of 16 (permalink) Old 06-24-2011, 04:38 PM
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Valves out of time or damaged.

Ultra-low compression.

Plugged exhaust pipe maybe.

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1985 VN750 Acquired Feb, 2011 - 13,676km
Mods - Ear Shave, Pickup Coil Gap, Drilled Clutch Basket, Shift Tie Rod, Mosfet R/R, MF Battery, De-Goated (H-Pipe), MCCT, Heated Grips, Plexistar 2 Windshield

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2004 KTM SX 125 - 1979 Can-Am Qualifier 250 - 1971 Kawasaki F6

Video Tutorials - Engine Rebuild - Fork Seal Replacement - Grease Swing Arm Bearings - Carb Rebuild - Spline Lube - Refilling Rear Shocks - Grease Steering Bearings
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post #7 of 16 (permalink) Old 06-24-2011, 04:40 PM Thread Starter
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Okay learned some more ****, if i hold the throttle barely open, the front cylinder will have good suction and will fire. There is no throttle cables on it, so I'm guessing that's causing the butterflies to be to far shut, am i crazy or does that make sence?
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post #8 of 16 (permalink) Old 06-24-2011, 10:27 PM
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Just guessing here but sounds like the carbs are way out of sync. Have you downloaded the repair manual? If so check out section 2-10.
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post #9 of 16 (permalink) Old 06-24-2011, 10:54 PM
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post #10 of 16 (permalink) Old 06-25-2011, 01:07 AM Thread Starter
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Can you supply me with a link to where i can download that repair manual?

If they were out of sync, would that make it fire on one cylinder at idle then run fine above idle?
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