Why are my pistons black?

So, I have finally started to disassemble my 1K. I will probably end up going with the 1075 pistons regardless of the cylinder condition (if steell can still get me a number for the place that has the kit). But I got the head off and noticed the tops of all four pistons are charred black. The spark plugs look pretty black as well. I really dont have very many miles on this since it was last taken apart and probably only a couple hundred or less on the plugs. What would cause this?


Also, my parts bike has a valve cover with air suction covers. What do these do? Would it be worth my while to use this valve cover instead of the stock one?


I will try to have pics in a little bit. Need to resize them.

kzrider.com/media/kunena/attachments/leg...07_0211Image0011.JPG [/img]

Post edited by: kztee, at: 2007/02/11 22:25

You might be running rich. Check the exhaust pipe end, and if it's black there, then it's soot. Soot = rich fuel mixture.

If it smokes when first started up, but goes away, then the valve guides are leaking.

Post edited by: CoreyClough, at: 2007/02/11 22:02

You have to smack me once in awhile to jar my memory

PM'd you the info.

I'm thinking somebody fabbed up some valve covers that are just blanks so you don't have to do the hose between them. Might try a search or someone will know.

Based on another thread I found, it looks like there used to be a hose running to the stock air box. I have pods now so this wouldn't work. What was the purpose of this hose? Should I stick with the original plan to have the stock valve cover chromed and keep it on the bike?

yeah thats a smog motor head on your parts engine,no real advantage to using a newer head unless its gpz/j motor head.id keep your origional one on there .carbon could be from many things if you are planning on boring it anyway i wouldnt worry much about it;)

pumps wrote:

I'm thinking somebody fabbed up some valve covers that are just blanks so you don't have to do the hose between them. Might try a search or someone will know.

$51.43 a pair at APE

if it looks like that afer a few miles, it is way rich, and looks to be burning oil as well, did you put new rings in?

Looks normal to me, with the rings that is. My 650 had rings like that. If it is dry and black, its all good. As for the valve cover, mine is like that on my 1000. Its no big deal and it works like a normal valve cover.

The stuff on top your piston crowns is called carbon. It is the result of incomplete combustion but your pistons don't look all that bad... it is pretty typical. The main reasons for the carbon are:
1. weak spark
2. poor compression
3. leaky valve stem oil seals
4. jetting adjustment of pilot mixture too rich; mostly pilot jet issue (or pilot mix screw or air screw)
5. spark plugs not correct heat range
6. using too high octane gas

The stuff can be cleaned easily with the pistons removed with a wire brush. Avoid hitting the sides of the pistons with the brush. You can also keep deposits to a minimum by using some Seafoam now and again and making sure issues listed above are not issues.