'97 VN800A bog/backfire - mixture adjust? - Kawasaki Vulcan Forum : Vulcan Forums
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post #1 of 7 (permalink) Old 08-18-2016, 09:53 PM Thread Starter
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'97 VN800A bog/backfire - mixture adjust?

Okay, for some background, check this thread:
https://www.vulcanforums.com/forums/5...e-w-video.html

I tightened the clamps for the hose between the carb and intake and that solved the issue I had mentioned in that thread, but the bike has never really run as smooth as it did when I first bought it several months ago.
The main problems now are a hesitation or bog at low throttle...and sometimes it just dies, but quickly restarts...and a backfire and burble on deceleration, which it never did before.

Is it possible that it's running too rich? Or too lean? Or...?

I did mess with the idle speed adjust a couple weeks ago, but that shouldn't cause the above issues I'm describing.

I'm open to suggestions and I can make a video over the next few days if it will help.
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post #2 of 7 (permalink) Old 08-19-2016, 01:02 AM
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Well, there's one more thing that still comes on my mind. Did You check Your carburetor Air Cut-Off Valve? The simplest reason for deceleration backfire sometimes is a damaged membrane or stuck valve. Sometimes it gives the backfire also on a cold engine start and acceleration.
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post #3 of 7 (permalink) Old 08-19-2016, 06:06 AM
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but the bike has never really run as smooth as it did when I first bought it several months ago.

so when you bought it until now, (besides the boot clamp bolts tightened up), was any changes done to the carb? or did you add a new set of pipes? new airbox?

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post #4 of 7 (permalink) Old 08-19-2016, 07:14 AM Thread Starter
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Quote:
Originally Posted by btom View Post
but the bike has never really run as smooth as it did when I first bought it several months ago.

so when you bought it until now, (besides the boot clamp bolts tightened up), was any changes done to the carb? or did you add a new set of pipes? new airbox?
No, it's exactly as purchased.
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post #5 of 7 (permalink) Old 08-27-2016, 01:28 PM Thread Starter
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Is it possible that I overtightened the carb-manifold hose?

I've read where doing so can cause an air leak? So, maybe I fixed one bad air leak only to create a smaller one?
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post #6 of 7 (permalink) Old 08-27-2016, 04:51 PM
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if you are in 1st gear and on acceleration to 2nd the bike hesitates that's a sign you need to open up the pilot mixture screw counter clock-wise, another indication is on deceleration from speed (closing throttle) and the motor backfires thru exhaust pipes, you need to remove the air entering the reed valves to the exhaust ports, you do that by removing gas tank and removing the epa air valve and tube going to both front and rear cylinder reed valves that are inside both cylinders, the epa air valve lets in fresh oxygen to the exhaust pipes to burn off any unburnt gas mixture entering the pipes

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post #7 of 7 (permalink) Old 03-24-2017, 10:00 PM Thread Starter
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An update:

Also, HUGE NEWS: I discovered why my bike was running so badly.
The dual clamp around the hose that mates the carb to the intake manifold? Well, one side got over tightened and worked its way off the hose, causing the hose to be misaligned with the intake and letting in gobs more air than should have been allowed.
I'd read about this very thing, but didn't suspect anything because I couldn't see the bottom of the hose and clamp UNTIL I removed the carb and hose.
I wondered why the ends of the two sides of the clamp were at different gaps when supposedly tightened.

I just reassembled everything and started the bike.
OMG! The thing started right up with no hesitation and bogging and idled perfectly even after sitting for 2 weeks in the cold.
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