Flame and decel popping from rear cylinder - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 06-28-2013, 06:27 PM Thread Starter
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Flame and decel popping from rear cylinder

Ok, I'm sure this is a rehash of some previous discussion but here goes... the bike I'm finishing returning to life has straight pipes (rear pipe is shorter than pipe from front cylinder but not by much since it has to bend down and under the bike to the right side), I have KN air pods and only the rear cylinder is popping with flames on deceleration. I do not have lean popping when slowly increasing RPMs from idle and have the air screw backed out about 3 full turns. I am unsure what the stock needle settings or jet sizes are but I know someone has been inside the carbs because they were put together wrong when I took them apart to clean them.

What I need to know is if someone is running a similar set up and if so, what size jets, what needle setting, etc... I'd hate to cook my exhaust valves shortly after returning the poor girl to life. Thanks in advance!
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post #2 of 6 (permalink) Old 06-28-2013, 07:25 PM
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Dude, if you can't resolve the decel pop on stock jets, you need to go up. Standard suggestion is 142 / 42 jets with 2 shims under each needle. I couldn't get the pop to go away on stock, not until I went up to the larger jets.

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post #3 of 6 (permalink) Old 06-28-2013, 08:21 PM
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Flames? AWESOME!!!

Yeah, you need to check what jets are installed and also check what plugs have been installed.

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post #4 of 6 (permalink) Old 06-28-2013, 08:25 PM Thread Starter
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plugs are NGK iridium and I'm pulling the carbs tomorrow when I get a chance because part of the problem is there is fuel dripping out of my rear exhaust pipe so I assume the float valve is stuck now in addition to it running lean.

Blaz- thanks for the sizes, I have quite an assortment of jets that will fit it but that gets me in the ball park much faster! I'll let ya'll know how she behaves once I go through the carbs again.

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post #5 of 6 (permalink) Old 06-28-2013, 08:32 PM
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Flames...cool...get a vid of it at night, eh ???

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pulling the carbs tomorrow when I get a chance because part of the problem is there is fuel dripping out of my rear exhaust pipe so I assume the float valve is stuck now in addition to it running lean.
If the float was stuck it would be running rich, not lean....fuel from the pipe is definitely signalling a stuck float....no rejet needed for that...try backblowing the carbs...if that dont work, rebuild em....why go to a higher jet, that will give you more fuel, when youre already dripping, lolol....make no sense at all...



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post #6 of 6 (permalink) Old 06-28-2013, 10:01 PM
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sounds like you have multiple issues.... sticky float and too small a pilot or clogged pilot? clean it up real good and log what jets ya got. With no baffles you will likely need to go larger jets then most, cause of the overall increased airflow.

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