kawasaki fd620d running rough

[robyb]

Recently picked up a conquest with the Kawasaki Fd620d. A few things are odd.

Symptoms:
Idles very low, but starts very well even in cold weather (-10ish?)
After initial startup, even if I let it warm up 3-5 minutes, it will want to die when I tough the throttle. I have to let it warm up a lot more than I should have to, before I can successfully use the throttle
Throttle is, not great. Sometimes it feels like everything is normal power wise for an instance and then quickly, it seems to struggle. From idle to throttle, it's like there's a spot where it has a lot of trouble, probably why it dies so easily when cold.
As I rev it up, it will stutter sometimes, and once in a while a decent puff of black smoke comes out.

What I checked:
Plugs look in good condition, they both have spark. I can't tell if it's weak or normal. Plug at back of engine is normal brownish, plug at front of engine is just black.
I re-gapped both plugs a bit more and I think that made the spark a bit stronger. I put them at 0.028 rather than the 0.024, so top of the range. They were initially at the bottom of the range. After this I had less of the big puffs of black smoke, but still quite hesitant.
Took apart carb, cleaned it all up with brake clean + compressed air. Everything looks good, it didn't look gunky from the get-go.
I put the mixture screw back in, then backed it out 1 1/4 turn.
My air filter area seems to have quite a bit of fuel. Is this normal?

I didn't spend any further time after that, still doesn't run great. Will have to go look at the spider nest of wires of course, but just wanted to put this out for the collective knowledge

Thanks in advance.

[Laird]

First thing to start with is do a compression check. Both cylinders should be within 10% of each other. These engines, meaning small 2 cylinder engines , have a decompression release for starting purposes so compression readings may seem on the low side. Fuel in the air filter is not normal. This could indicate that the float valve in the carb may not be set right among other things. The setting of the carb at 1 1/4 turns is just a starting point. You may have to screw it in a bit or out a bit. Sounds like the front cylinder is being flooded or the plug is not firing properly. I would put a new set of plugs in or at least the front one, or try swapping plugs. Once it is running pull the spark plug wires one at a time to make sure it is running on both cylinders. Low compression will also effect the burn of the front cylinder. A spark tester could give you a better idea of your spark performance. First though do a compression check.

[Laird]

Added note to the above reply, make sure the spark plugs are grounded when you do a compression check as there is a chance of blowing a coil or modual.

[robyb]

I don't know how great my comp check will have been at non-room temp, as my garage is full of other projects right now. But in yesterday's sub-zero temp I tested 90 front, 105 back. May have to wait till I have the car back together and bring it in the garage to do a proper comp test... or maybe we think the cold doesn't matter... my engine needs a rebuild regardless?

In the manual it says the flywheel has some markings to line up TDC. No clue how I'd even see those with the engine in the argo. Seems silly that one would have to pull an engine to setup valve lash, to make sure my issue isn't with valves sticking open (doubtful). Didn't feel like looking further, fingers were getting frozen :P

[ARGOJIM]

I think I would start by removing the fuel line at carb and fill a small water bottle to see how much water is in the fuel as it will do stupid stuff to small engines. If that is good with no water, start the machine and once you can bring the rpms up run it at near full throttle for 1\2 hr or so to clean all the deal out of valvetrain. Shut it down and see what you have .Kawasaki are bad fuel testy and valves him up, they are also cold blooded