Lost power, gasoline from carb boot - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 20 (permalink) Old 08-14-2018, 04:26 PM Thread Starter
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Lost power, gasoline from carb boot

So I was riding on the highway earlier when suddenly, the bike began to slow down and lose power. I limped it home at about 30mph the whole way, having to keep the throttle fully open. I checked for spark, spark was ok. There is gasoline coming out of the carburetor boot on the cylinder head, and out of the intake. Anyone know what this could be?
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post #2 of 20 (permalink) Old 08-14-2018, 05:09 PM
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Stuck float, likely.

Tap on a solid area of that carb with the handle end of a big screwdriver.

But not hard enough to dent or bend anything.

Sometimes that'll make it let go.
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post #3 of 20 (permalink) Old 08-15-2018, 10:41 AM
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Look in the carburation board for a sticky titled "Wolfie's back blow method"

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post #4 of 20 (permalink) Old 08-16-2018, 04:38 PM Thread Starter
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Well, tried blowing it out, tried removing the bowls to spray carb cleaner, no luck. At idle it still refuses to review past 4k, and the rear cylinder misfires. The left carb still has gas coming out the intake. It also pops at the carb/airbox when I give throttle... What would the next step be? Remove the carb entirely? Or should I investigate a possible cylinder issue?

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post #5 of 20 (permalink) Old 08-16-2018, 05:17 PM
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Yep, remove carbs, remove bowls, remove dirt. Need to pull the float and float valve to get to the chunk of dirt holding the float open.

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post #6 of 20 (permalink) Old 08-17-2018, 02:10 PM Thread Starter
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So before I event pulled the carb I decided to perform a compression test. Front cylinder had 180, rear cylinder, zero. Looks like the motor is toasted....
Honestly not sure if I feel like doing a rebuild, so might be time for a new bike....
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post #7 of 20 (permalink) Old 08-17-2018, 03:59 PM
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So before I event pulled the carb I decided to perform a compression test. Front cylinder had 180, rear cylinder, zero. Looks like the motor is toasted....
Honestly not sure if I feel like doing a rebuild, so might be time for a new bike....
Did not see that coming.

No noises before or after, just sudden loss of power?

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post #8 of 20 (permalink) Old 08-17-2018, 04:37 PM Thread Starter
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Quote:
Originally Posted by SergheiS View Post
So before I event pulled the carb I decided to perform a compression test. Front cylinder had 180, rear cylinder, zero. Looks like the motor is toasted....
Honestly not sure if I feel like doing a rebuild, so might be time for a new bike....
Did not see that coming.

No noises before or after, just sudden loss of power?
No odd noises at all, just lost power on the highway, wouldn't rev past 4000 RPM, and wouldn't drive past 30-40 mph. It did shoot some oil out of the carb boot which gave a hint, but I wanted to confirm. The rear spark plugs were also oily. It had been burning oil from the rear cylinder for a while, I just never expected it to completely give in.
The only odd noise was popping out of somewhere on the top end when I revved it at idle.
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post #9 of 20 (permalink) Old 08-17-2018, 05:00 PM
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No odd noises at all, just lost power on the highway, wouldn't rev past 4000 RPM, and wouldn't drive past 30-40 mph. It did shoot some oil out of the carb boot which gave a hint, but I wanted to confirm. The rear spark plugs were also oily. It had been burning oil from the rear cylinder for a while, I just never expected it to completely give in.
The only odd noise was popping out of somewhere on the top end when I revved it at idle.
This is one of those where I'd have to pull the cylinder apart just out of curiosity. Sounds like it has a piston failure of some sort. Could be the head itself but I'd expect some noise. The popping makes me think intake valve. ... broken valve spring or stuck valve? ... valve fractures piston... oiling, excess unburned fuel, and loss of compression.

Stuck/dropped/broken valves seem to be the most common catastrophic failure on this engine. Not that it's an epidemic, but almost the only failure that happens.

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post #10 of 20 (permalink) Old 08-17-2018, 05:03 PM
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Sounds like the intake valve is MIA. They usually take out other parts if they break however...so would be interested in the postmortem exam.

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