Marbling - Idle issue - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 04-25-2014, 08:24 PM Thread Starter
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Marbling - Idle issue

Okay, so I feel like I've read through every thread on here about marbling, and the carb fuel adjustment screws. Here's what I did (the bike is pretty much stock, exhaust included):
-Marbled the two lines running to the emissions pod
-removed the vac line from the rear carb to the pod, capping both sides
-Adjusted each mix screw to 2.5 turns out.

Now, the idle is very inconsistent, fluctuating from about 1000 to 1200 back and forth. It sounds like the rear cylinder is missing most of its strokes. Adjusting the rear carb screw a full turn in either direction does not seem to affect the idle or inconsistency.

Note that this is my first time adjusting anything carburetor related - so if there is something obvious I missed, please let me know.

Thanks!!! Mark

2006 VN750
Tim Parrott Stator
Mosfet R/R
NGK Iridium plugs
Drilled Clutch Basket
TOC rebuilt ACCT springs
Splines lubed
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post #2 of 7 (permalink) Old 04-25-2014, 10:13 PM
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Sound like a possible vacuum leak somewhere...do a smoke test on it with the engine running...also, spray a lil WD-40 on the carb to head boots...if the idle changes temp, you foud it....if the smoke sucks in, you found it....

You can try doing a backblow on the carbs too, but that (dirt) shouldnt cause fluctuation in idle....Im leaning towards a vac leak somewhere....



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post #3 of 7 (permalink) Old 04-25-2014, 11:28 PM Thread Starter
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Thanks for the response... I'll give those two things a try tomorrow. Can marbling make carb problems more prominent?

I guess I should add the following to my timeline (forgot to specify):

-Bike was dumped on its right side from standing (girlfriend, haha)... it only laid on its side for a few seconds, but less than a cup of gas spilled from somewhere around the carbs
-started and idled fine an hour later... did not notice any odd idle, but then again I didn't check closely.

...4 days later...

-Marbled the two lines running to the emissions pod
-removed the vac line from the rear carb to the pod, capping both sides
-Adjusted each mix screw to 2.5 turns out.

took it for a ride about 15 minutes which let me know that it was feeling odd still.

2006 VN750
Tim Parrott Stator
Mosfet R/R
NGK Iridium plugs
Drilled Clutch Basket
TOC rebuilt ACCT springs
Splines lubed
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post #4 of 7 (permalink) Old 04-25-2014, 11:34 PM
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NOW that ya mention the bike falling over........this will cause an air bubble to form in the cooling system....that DOES and will affect idle....you need to burp it.....my ol Bessie been on her side plenny of times...and whenever I didnt burp her, she ran rough....you'd be amazed once you bleed the system....just do a search on "burp" and "bleeding"....might even be a sticky in the cooling section....

I wish ya had said that right away, lol.....



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post #5 of 7 (permalink) Old 04-26-2014, 08:40 AM Thread Starter
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Hahahah I read another few of your posts about bleeding the cooling system after a tip, but while I was futzing with the carbs after marbling, and test riding the bike was too warm and I didn't want to open the radiator cap. I'll bleed it this morning and follow up.

Thanks Wolfie.

2006 VN750
Tim Parrott Stator
Mosfet R/R
NGK Iridium plugs
Drilled Clutch Basket
TOC rebuilt ACCT springs
Splines lubed
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post #6 of 7 (permalink) Old 04-26-2014, 01:50 PM Thread Starter
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I just bled the cooling system... didn't notice any significant air from the bleed valve though. left pipe is still popping significantly at idle... it really feels like it is missing each stroke and the bike is idling only on the front cylinder. I took a video of the sound, let's see if it came out:

https://www.youtube.com/watch?v=Fpfuw5buMQ4
(the video is sideways now but it should be rotated shortly... working on it.)

Adjusting the mix screw for the back cylinder one turn in either direction does not seem to affect the issue.

2006 VN750
Tim Parrott Stator
Mosfet R/R
NGK Iridium plugs
Drilled Clutch Basket
TOC rebuilt ACCT springs
Splines lubed
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post #7 of 7 (permalink) Old 04-26-2014, 07:21 PM
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You wanna bleed it using that bleeder by the thermostat intil you get a stream, engine runnin....if its poppin a lot from one cyl....check the exhaust connection by that particular head first....if thats fine, open up the idle screw on the carb for that head another 1/4 turn......also....low voltage will cause backfiring as will bad plug wires.....check all them too....check yer battery output off and runnin both at the battery....a cracked coil can cause it too, but its very rare....



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