Carbon deposits on only one piston crown??

[shizznats]

After doing a top end rebuild and replacing the pistons/rings/gaskets/plugs, we ran our LTD motor for about an hour or two total to adjust carbs and get it running right. The majority of that was at idle and we were running on 40:1 premix plus whatever the oil pump delivers. When we pulled the plugs the other day to take a look at them, I noticed something strange. I looked in the spark plug holes and saw that the clutch side piston has a layer of black deposits on it (maybe 1.25" in diameter in the center of the crown of the piston) while the mag side piston crown is perfectly clean. Also, all 4 plugs look fairly dark, but I'm certainly no expert when it comes to reading plugs. The electrode, ground strap and porcelain all have a "dry" flat black look to them. Not tan like I'm used to seeing on my car. Also, the two plugs from the clutch side are a bit darker and have some of the flat black on the base ring as well. See pictures below... the top plug is from the mag side (the clean piston) and the bottom plug is from the clutch side.

Based on this, my guess is the engine is running rich (this short time we had it running since our rebuild was in fairly warm conditions @ ~70-85 deg F). But what's more worrying is that only one piston has what appear to be carbon deposits on its crown. So, a few questions for you guys:

- Is it normal for there to be noticeable deposits on a piston after only about an hour of running? Or would one expect the piston crown to look rather clean? What could this indicate?
- Is it possible that there is a head gasket leaking into the mag side cylinder through the head gasket ring and "steam cleaning" the top of that piston making it so clean? What other symptoms would there be if there was a head gasket leak like this?

I'm really just trying to figure out which cylinder there is a problem with and which one appears to be running somewhat normal. The engine seems to idle fine and seems to run ok though I haven't done extensive running with it to be able to tell if it's underpowered or not.

As always, thank you!

[thomy]

How old are the seals on the crank? On every Kawasaki engine that I've taken apart since March, 5 of them, the mag seal was blown.

[shizznats]

Both crank seals were replaced. Engine passed a crankcase pressure test. Compression is a hair under 135 on each cylinder.

[Interceptor398]

Maybe running a bit rich on one side?

[gixxer6]

Being that most of the running was at idle, I would guess that the carbs aren't synchronized perfectly.  One cylinder is pulling harder than the other and/or running richer. 

As far as a blown head gasket steam cleaning the top, if there was water getting in there, the plugs would be white. 

I would expect a little black buildup on the pistons from running the extra oil. 

[shizznats]

Being that most of the running was at idle, I would guess that the carbs aren't synchronized perfectly.  One cylinder is pulling harder than the other and/or running richer. 

As far as a blown head gasket steam cleaning the top, if there was water getting in there, the plugs would be white. 

I would expect a little black buildup on the pistons from running the extra oil.

Thanks guys. Also, if there was a head gasket leak, I'd have lower compression on that cylinder, right?

Should the accelerator pumps be squirting fuel at idle? I have the Keihins

[kawhead]

no squirt at idle.....bad diapharm or check.....