Stumbling/power loss under load - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 09-09-2008, 01:12 AM Thread Starter
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Stumbling/power loss under load

Hey, everybody. Bought a 2001 VN750 in May and I'm loving it (except for the seat!).

It's giving me trouble under high load in higher gears and at mid to higher rpm. It tends to stumble a bit and lose power. If I keep the throttle wide open, it just keeps up with the stumbling and less than expected acceleration. It doesn't stumble and then recover, like it might with a temporary lean condition.

It runs just fine as long as I avoid high load (wide throttle) at mid to high RPMs in the upper gears. No problems starting, hot or cold, and no problems idling, and no problems with how it feels or with power at lower RPM at partial throttle. In fact, in my daily commute, I generally never experience the problem unless I intentionally go out of my way to test it.

I'm getting 50 MPG on my daily commute, which is 35-50 mph for 17 miles each way.

On our first road trip recently, with a pretty good load and two up, it was hard to even keep 40 mpg, being generally high 30's unless I really kept the speed down (below 60 mph). On one tank, at around 75-80 mph, I didn't even get 30, but there was a lot of wind.

The plugs look OK, being generally brownish, with no sign of running rich or lean.

Any ideas on where to start looking?

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post #2 of 4 (permalink) Old 09-09-2008, 06:37 AM
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Easiest thing to check is your carburetor vent line - it runs out the right side of the engine and the vent settles into the right airbox. Often it will bottom out against the box, and then your carb can't vent properly - some folks recommend cutting the tube at a 45-degree angle, which prevents bottoming out. I had the same problem coming home from work yesterday and just fiddled with the tube as I rode until I could find a spot where the stumbling stopped.

Good luck!

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post #3 of 4 (permalink) Old 09-09-2008, 06:32 PM
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I had problems with my bike (85 VN700) and the carb vent line on my doesnt run into the right ear... it runs to a fixture on the bottom side of the gas take under the fuel sending unit. (Thanks Glenn, I would have never looked under the gas tank) Tried that vent line in the ear, in the open, plugged... same results... idle fine then sputter sputter sputter at mid to high RPM. Don't know if that helps but I tried.
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post #4 of 4 (permalink) Old 10-03-2008, 07:13 PM
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Had my first issue with "stumbling" this week. Not having a clue why this was happening, I went to the bible "VN750 Forums" and there it was, carb vent 1:1

You guys saved me many hours of "stumbling" around the bike pulling plugs, wires, filters, and what's left of my hair out. I did the angle cut on the hose and the bike runs great. Thanks!

The Flag on my bike honors those who serve our Country and those who have served!
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