1993 Kawasaki Vulcan running oddly

[Jeffsg605]

Primary resistance spec: 1.8-2.2 ohms
My resistance: 2.5 ohms for both coils

Secondary resistance spec: 19k-29k ohms
My resistance: 31.8k and 33.4k

But I may have just found my problem. I took readings again to answer your question and it was tough to get a secondary number out of the front coil. With the boots off, both coils are around 22k ohms. Do you think a loose or corroded boot would cause this problem? I think its worth replacing.

Also I just noticed the front left spark plug wire had a bunch of blue dust inside it. Could this be a sign of a bad connection?

[Johnj]

That's not enough of a difference. Change out those plug wires.

[Jeffsg605]

I changed all plugs and two plug wires. It now idles well and revs clear up to 5k but it still intermittently stops there. When riding it, it intermittently loses power. I'm going to change the two remaining plug wires but I don't think that will cure it. I noticed there are three small exhaust leaks, two in one pipe, one in the other. I don't feel that would cause an intermittent problem but could it be contributing? I'm starting to really be at a loss here. I'm going to check compression as well. I've heard valves not seating correctly can cause this.

[GS_in_CO]

Also I just noticed the front left spark plug wire had a bunch of blue dust inside it. Could this be a sign of a bad connection?

Blue dust is totally corroded copper. This is evidence of a bad connection or conductor in that wire.

(Windex window cleaner is blue because it has some copper dissolved in it.)

[Jeffsg605]

I will definitely change the other two plug caps then, thanks. They all had a little blue dust to them.

[Jeffsg605]

I changed all the caps. It idles better but I still have a running problem. I changed the spark plugs and rode the bike for about 15 miles. It still intermittently loses power. I pulled the plugs and they are all super white indicating a lean condition. The thing that confuses me is that they are all evenly white. I take this to mean that there is a problem before any air or fuel reaches the carbs. I know the fuel petcock is clean and allows fuel to flow freely to the bowls. Maybe a vacuum leak somewhere then? I can't seem to find any though. Any ideas where to look?
Thanks a lot for your help so far guys.

[GS_in_CO]

intermittent is a key point.

Vacuum leak generally isn't intermittent unless things are shifting mechanically as you ride.
Too lean across all plugs (and all carbs? this has multiple carbs or a single?) suggests something common across all cylinders like fuel supply. An intermittently plugging petcock or fuel line? (big flake of something that sloshes around and restricts flow sometimes?)

I've not tried this but consider using spray WD40 or carb cleaner around the seams and joints of the air intakes while the bike is idling. If the idle changes, the hydrocarbons getting sucked into the vacuum leak will change the idle. If no leak, you just have a small mess Careful with flammability though. Have fire extinguisher handy.
The mechanic's standard is to apply mapp gas around suspected leak areas.
You also might be able to feel it but -- not as reliable.

I've actually wondered about the validity of plug chops with unleaded fuel. But I have no answers on that.

[Jeffsg605]

Too lean across all plugs (and all carbs? this has multiple carbs or a single?) suggests something common across all cylinders like fuel supply

It's two carbs with two plugs per cylinder. I blew air through the fuel petcock and it seemed clear. Maybe I'll take it apart and clean it out again.

The WD40 sounds like a good idea too. I'll try that this weekend. I think I'm pulling in air at higher RPM. The bike idles and cruises below 3k RPM absolutely fine but whenever there is load on the engine, it starts to bog. Is there more vacuum at some part of the carb or intake system during high RPM revving? I thought vacuum was highest at idle which would contradict the problem I'm having.

[par4sure]

Not a solution, but I also have a 86 750 Vulcan and changed the rectifier/regulator, and now my bike is doing the same thing. It seems sluggish at around 40-50. Before changing it, the bike ran fine.

[GS_in_CO]

I think I'm pulling in air at higher RPM. The bike idles and cruises below 3k RPM absolutely fine but whenever there is load on the engine, it starts to bog. Is there more vacuum at some part of the carb or intake system during high RPM revving? I thought vacuum was highest at idle which would contradict the problem I'm having.

High power (throttle open) means less vacuum as you correctly understand.

Typically loss of power at open throttle is due to weak ignition. Spark can't jump as far thru fuel/air mixture as thru vacuum (air is an insulator compared to vacuum).

Weak ignition could be plugs gapped too widely or coil not putting out full energy. (corroded connections on the primary side or partially shorted windings in the coil)

It's possible that you are supposed to have a timing advance with higher RPM and that's not working. Cars with distributors had flyweights that shifted timing with higher RPM. I don't know what your bike has but it surely has some method of doing the same thing.