Hesitation with low throttle at cruising speeds - Page 2 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #11 of 17 (permalink) Old 05-05-2020, 07:50 PM
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Wet vac line will mean the carb is getting it's fuel from somewhere it shouldn't, and usually ends up filling the crannkcase with gas even parked with the petcock turned off. Means the diaphragm is toast.

What the heck kind of plug is that? Hard to tell what's actually on it, but the construction is something I haven't seen.

The o-rings for plug wells can leak, and there are holes at the bottom of each jug to let the oil leak out, front/rear. When you pull the plug out, you can be drawing it through oil if leaking.

Run it in the dark and look for spark around the plug wires, boots, plug wells, and throttle cables especially. Right now mine is sparking off the cables and I see flashes around at least one boot.

The plug boots on this engine have resistors in them, (thank ye wolfie), couple posts here about it. Tell me about your plugs, I wonder if those play well with the resistors. It's coming to me.. are those E3 plugs?

I've seen very few bad plugs in the past 15-20 years, but 've seen mpg drop from a switch to platinums. Usually Bosch. Denso doesn't strike me as the best plug, but that's what came with the bike and I just left them in there the past 6 years.

2003-21k mi
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__________________________________________________ ____________
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post #12 of 17 (permalink) Old 05-05-2020, 10:36 PM Thread Starter
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Hey there, the plugs say E3.36. Curious about having two spark plugs per cylinder. What’s the point of that?
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post #13 of 17 (permalink) Old 05-06-2020, 02:08 AM
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Better ignition, flame propagation, combustion, efficiency.

you can pull just one plug each cylinder to read color or check compression... The easy ones.

I'll have to visit E3, I remember that bridge on the electrode, seems it might shield. Have watched them spark?

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
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post #14 of 17 (permalink) Old 05-06-2020, 04:46 AM Thread Starter
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I haven’t watched them spark. I checked for spark in the plug sockets in the garage with the lights off (covered the headlight best I could) and didn’t see anything. Is the other method to pull them and see is they spark while holding them in the cable?

Appreciate the replies and help. Also, think it might be the carb vent tube? I feel like this problem might be more related to the speed I’m going versus a specific rom range. Is it possible that even though it’s been cut and is positioned in the right ear, it’s still experiencing turbulent airflow? I don’t really get it, it’s supposed to be ambient air but it’s in the air box with a slit in it and air is rushing through into the carbs/engine. Is there something about the geometry of the air box that prevents this turbulent air from hitting that particular location?

Going to pop off the tank tomorrow and make sure all those hoses look okay. Also added some Berrymans chem tool so hope this does the trick. Bike runs great, just this problem.
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post #15 of 17 (permalink) Old 05-06-2020, 05:36 AM
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The filter housing slot is fairly sheltered. Factory likes it. But it's pretty simple to move, just pull the hose over to the frame tube under the tank, or if enough hose, the cover on the fuel gauge sender.

Yeah just pull a plug, lay it touching engine, crank. Spark should be mostly blue and have a good snap to it. If it's yellow/orange and just lights up with no snap, it's not good. Probably not the plugs, never hurts to check.

Run the berry man and run it in out of it's hesitation. Can you predict when it will act up?

Subtle hesitation makes me think about the diaphragms, should try the search, do the woosh test before removing.

Don't believe I've ever timed out while posting, and the site saves a draft using Firefox. I may take hours to finish one sometimes.

Been looking at my bike pics. Every time I look at Christine, I want jump her bones. The forum should do another Rides Pic thread this season, your bike, where you went in the background, it was fun. Glenn put up the prizes, wish I would've kept mine

Got lost in pics when I figured out how to stream pics to my TV
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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
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post #16 of 17 (permalink) Old 05-07-2020, 10:59 PM Thread Starter
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Solved! Ended up being a bad spark plug, what a relief.
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post #17 of 17 (permalink) Old 05-08-2020, 12:28 AM
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Quote:
Originally Posted by Amir Razai View Post
Solved! Ended up being a bad spark plug, what a relief.
Edit: this is turning into an epidemic, two bad plugs, a day after I said finding a bad plug is rare these days.

Wonder what brand they were?
Probably Denso, the ones I left in mine are Denso.

Found the quote and edit buttons! Thanks Jason!

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

Last edited by Spockster; 05-08-2020 at 12:37 AM.
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