hard starting, starting on one cylinder - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 07-30-2019, 08:17 PM Thread Starter
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hard starting, starting on one cylinder

I have had this issue now on 3 Vulcan 750s. I believe I now know why it happens. I have been starting the engine up and letting it idle for a while every once in a while on my '97, even though it is not yet rideable. I notice that if I start it every day, it fires right up and runs smooth. But if I let it sit for several days before starting it, it takes a lot of cranking to get it started, it will often backfire a couple of times, and often starts up on the front cylinder only. I have had this issue since 1993, for almost 200,000 miles. It finally dawned on me what may be causing it. While sitting, the gas evaporates out of the float bowls (ethanol gas evaporates even faster than real gas) and because it has a vacuum petcock, it can take some time to fill the float bowls back up again, as gas only comes out while the engine is being cranked. And apparently the front float bowl fills up first. It starts up on the front cylinder, then about 10 seconds later the rear cylinder kicks in. Recently after it had been sitting for about a week, I put a small amount of gas into the carbs through the float bowl vent hose. It fired right up and ran fine. I am definitely getting rid of that vacuum petcock (it's too bad they removed the "prime" position, it should have been obvious it was there for a reason) and going to a TW200 petcock.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #2 of 4 (permalink) Old 07-30-2019, 08:34 PM
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Bump and Pause, I forget exactly what Paulywog called it.

If you know it's going to be a dry start, crank the starter for a few turns to make some vacuum, pause and give the fuel time to flow a bit. Rinse, repeat, can take few times if the carbs are dry. Works for me.

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post #3 of 4 (permalink) Old 07-30-2019, 09:31 PM Thread Starter
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Yes it works, but too complicated, takes too long, and is hard on the starter. If I can get both float bowls full, it will start right up as soon as I hit the starter button. Now to find the thread on the TW conversion. To bad that original petcock with the prime position is no longer available. An alternative (at home) would be to pull the vacuum hose off the front carb and apply vacuum to it for a few seconds.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
VN750Rider/Jerry is offline  
 
post #4 of 4 (permalink) Old 07-30-2019, 09:36 PM
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Complicated, really? Takes too long?

Not hard on the starter, it's actually the prescribed way to use a starter. Long cranking is what's hard on the starter.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
Spockster is offline  
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