KZ650 rough idle, hunting, pop and dies when hot

What is the voltage with everything on?
Steve

cjaldous wrote: Measured the battery this morning. It measured 12.5.
I pulled two plugs. #1 was brownish. #4 was black.

Here's a selection of thoughts I have:

Should I go back to 3 ohm coils? (I bought 5 ohm because dyna says they are for street use.)
I was also convinced that 5 ohm coils would be easier on the charging system. I have Dyna S ignition.
Certainly my stock 15 pilots can't be too rich. Is it possible my mains are rich, and putting carbon on the plugs at high rpms?

Sorry for wandering between carbs and ignition.

Does 1 and 4 fire at the same time? If yes, IMHO, you don't have a coil problem, you have a carburetor, intake/exhaust valve-valve lash issue, plug wire or actual spark plug problem.

With the ignition and engine switch on I get 12.2 at the battery and 11.8 at the coil.
When running my voltage and current is within spec according to the FSM.

Plug wires and caps are new (7mm dyna copper). Plugs "were" new, but have been carboned up quite a few times now.
Valve clearance measured fine, but could be checked again.

cjaldous wrote: . . . Fuel level on carb 3 now measures 4-5mm below the lip.
I've noticed that if I set the fuel level any higher (float level lower) that the floats are bottoming out inside the carb body. . . .

Is it possible with the carbs at hand that one or more of the floats could be installed upside down?

Good Fortune!

Patton, I thought about that too. All the floats are installed so the ledges on the inside of the floats are facing up (towards the carb body). All of the float arms have similar angles when compared to the floats.

It seems that any combination of float bend and tab bend resulting in the same float height should yield similar fuel level characteristics, within reason of course.

I had a somewhat similar issue on my 650 a little while ago. I'm not sure what kind of plugs you're running, but my NGK'S failed on me (on multiple cylinders). What I mean by "failed" is that they still sparked, but weaker, and off to the side of the plug, not on the electrode tip. The bike would run, but the plugs would foul, and once warm it wouldn't like running. Switched over to fresh Champions, and she fires right up, no more poor running. Just a thought. Take the plugs out, rest them on the head to ground, and see what you have for spark on each plug. Good luck!

Thanks 650, I've thought about putting in clean plugs, it's only $10 so it's probably worth a try. Maybe I've messed up my new plugs so bad that they spark poorly. I've checked spark very recently, and they seemed ok, but I know under compression that can change.

I noticed something today while adjusting the pilot air screws.

One thing I notice is that the idle doesn't change when I remove the pods. 2nd is that the exhaust pressure from 3&4 is much less than 1&2. If I put my hand over 1 or 2 carb throat the bike almost instantly dies. If I put my hand over 3 or 4 I can feel the carb suck my hand, but the engine speed doesn't change. This seems really odd to me. So odd that as I type this I'm afraid of sounding like a complete idiot.

Let me go try that again.

I haven't done a sync, just an eye ball bench sync when I was checking the needle positions.

I just tried closing off the carbs again, and blocking #4 has no effect. My palm gets sucked in, but the engine doesn't respond.
Closing #3 has some effect, and closing #1 or #2 will cause an almost immediate stall.

This would seem to indicate that I have a valve problem, right? Or perhaps the engine is only running on 1,2 and 3 so blocking #4 has no bearing on the rpm?

I'm going to go get 4 new B8ES plugs.

Valve problem? No, not at all; that's not what I would think it indicates. I would think it means the carbs are dirty and not passing any fuel to the cylinders even though the cylinders are sucking air through the carbs, pr maybe the carbs aren't getting ant fuel. I would very carefully clean the carbs and see if that helps. Ed

Thanks Ed.

Advanced Auto didn't have 4 B8ESs so I bought B7ESs. While taking my 8s out I noticed they had cleaned up a bit except for #4. They were dark brown, #4 was still black. I put the 7s in and went for a short ride. Pulling a couple plugs showed them to be very, very clean with almost no change in color. This probably means they're too hot, right? The plugs I pulled didn't have any white deposits, they were just very clean.

I decided to give B7ESs a try because I found a post where you said switching to B7ESs solved your carbon issue, The engine still didn't respond to me blocking carb #4, but plug #4 does show some evidence of combustion.

Tomorrow I'm going to get the engine warm and adjust the air pilots and try a sync.

I'd synch first then try lowering the needles, very low intake vacuum could be a couple badly out.

With ignition switched on, and plugs removed and held grounded against the engine head while spinning over the engine, do all the plugs have healthy fat blue sparks?

Good Fortune!