Front cylinder runs hard and hot, as it should, rear is only warm and not nearly as l - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 07-26-2018, 09:18 AM Thread Starter
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Front cylinder runs hard and hot, as it should, rear is only warm and not nearly as l

A few days ago, a day before my 18th birthday I went out and picked up a 1986 Vulcan 750. Not to bad of shape. Fired it up last night, and the rear cylinder feels weak, like when I rev it up and put my hand behind the front cylinder exhaust, it moves my hand back with authority and gets hot, while the rear cylinder feels weak and is nowhere near as warm, but it is still running. Could this be a faulty plug, carburetor, or is the rear cylinder not getting enough air? Thanks in advance
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post #2 of 7 (permalink) Old 07-26-2018, 09:41 AM
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Dirty carb is the number one suspect.

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post #3 of 7 (permalink) Old 07-26-2018, 09:34 PM
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+1.

Vulcan's got two plugs in each cylinder. Doesn't seem likely that both would fail at the same time. You could switch plugs around if you want to be thorough, but I think Spockster has it nailed.

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post #4 of 7 (permalink) Old 07-26-2018, 11:15 PM
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You can also check the air filters to make sure the foam isn't falling apart and getting sucked into the air ducts and carbs, but that should affect both carbs.

If the rear cylinder is still making some power, a dose of seafoam might clean it out. If the cylinder is dead, and the carb is clogged, have to take the carbs off.

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post #5 of 7 (permalink) Old 07-27-2018, 09:45 AM
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Yes, the original air filters are foam. You definitely will want to check them. Have had several different bikes w/ rotted filters.

My Vulcan had what looked like breakfast cereal in one of the filters when I bought it. Some rodent was stocking up for the winter! Also had an especially heavy coating of some bluish-colored greasy substance. I figure some former owner or mechanic had given those filters a liberal dose of Belray filter spray or the like. I don't think having that much product clogging up air-flow was doing me any favors, so cleaned out filter w/ dish soap and water, dried them, soaked w/ motor oil and then squeezed out as much oil as I could w/ a rag. Should have a little better air-flow that way while still protecting the engine. . . .

I'm running stock filters and stock exhaust. Got just over 50mpg w/ it 2 weeks back on my trip when we were sight-seeing. It doesn't normally do quite that well, but starts, runs and revs good.

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post #6 of 7 (permalink) Old 07-27-2018, 11:11 AM
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Gimme fuel, gimme fire, gimme that which i desire. Vrooooommm. I'd suspect float height as well.
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post #7 of 7 (permalink) Old 07-27-2018, 09:08 PM
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Do you smell gas???are plugs wet? Could possibly have a sticky float needle in the carb for the rear cylinder, causing it to flood out.look up a sticky in the carb section called Wolfie's back blow method. While you're at it,can you please give us an introduction in the newbie section?

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