Rear cylinder not firing?? - Kawasaki Motorcycle Forums
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post #1 of 3 (permalink) Old 06-08-2017, 12:38 AM Thread Starter
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Rear cylinder not firing??

The rear cylinder on my 2004 vulcan 800 isn't firing off?? This happens every couple months and after replacing the fouled up spark plug, it would work for a while, but spit out white smoke/blue smoke (It's hard to tell, but it's smokey. Eh maybe more blue) while it did work. Last year I replaced the ignition coils, rebuilt the carb, and rebuilt petcock.

The other day after pulling the plug out the plug, I notice the wire wasn't connected into the coil, after fixing that the spark plug sparks like crazy when I ground it to the frame. But still no power, and no heat from the exhaust. There's only one carb and if that is the problem why isn't it a problem for the front cylinder?

Currently waiting on an adapter for the compression tester

More info to come
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post #2 of 3 (permalink) Old 06-08-2017, 03:04 AM
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There are two characteristics of the VN800 engine that may be relevant to your problem:

1) The 800 engine is NOT a high compression engine that needs high octane. It prefers regular 87 octane.
No two engines are exactly alike, but it's quite possible to induce severe carbon deposits using high octane fuel in the 800.

2) The rear cylinder runs richer (and cooler) than the front cylinder.
In most cases, this doesn't matter much, but some owners report plug fouling in the rear cylinder.

I'm going to take a guess here, and it won't cost you much to give it a try:

1) If you're using high octane, stop doing that.
If you tend to lug your engine, stop doing that.

2) Go up one step in heat range to a hotter plug: NGK CR6E.

And it wouldn't hurt to run some Seafoam in your gas in case you have severe carbon deposits.
Go wring out the engine and resist upshifting too soon.

Like I said, I'm guessing, but there you are.
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post #3 of 3 (permalink) Old 06-08-2017, 09:11 AM
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Installing a hotter plug in rear cylinder just covers up the underlying problem:

1. Fuel tap is leaking, or
2. Carb needs work, or
3. Both.

If it was an inherent problem, the rear plug would have fouled out the show room door, and they didn't.

When were the valves checked last?
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