Low compression, oil out the breather. kz900/1000

What am I looking at?
Steve

You are looking at the shiny spot on the ringland between the top 2 rings that's worn and shiny.
The top ring was fine, the oil ring was fine.
The middle ring was stuck.

Doesn't look too bad to me. What do the piston skirts look like and the bores? Also the combustion chambers.
Steve

Here ya go.








The chambers have been holding kerosene with no leaks for about 5 hours.

#2 cyl had low compresssion and a very tight intake valve, so i hope that's the cause.
#3 cyl was leaking down into the case, stuck ring.

The bores and skirts look ok to me (yes they could always be better).

I still need to id the piston, it has some markings that I'll try to upload in a bit. They measure 71.5mm

I'd take a good piston and measure them upside down in the bores top, middle and bottom with a feeler gauge. Could be new rings and they will be runnable.
Steve

"C" stamped on the piston top.
"41?5" on one side and "7?" on the other on the bottom where the wrist pin goes thru.

What is that ring in the valve pocket? MTC pistons?
Steve

swest wrote: What is that ring in the valve pocket? MTC pistons?
Steve

I'm afraid you will have to tell me, haha! It's my first rodeo!

Both rings are marked "n100".

Maybe nothing. Might be too many dry starts.
Steve

Ok, cylinders are off to get honed, pistons have been identified as Wiseco 1075 pistons for a 72mm bore. I've got a big Z1 enterprises order placed for all the gaskets I'll need along with 4 new Wiseco ring sets.

I'm not going to use copper base and head gaskets. The fiber head gasket I have coming is a one piece design, of the same thickness as the copper. I understand this means I need to seal the o-ring channel and possibly shave down the rubber pads on the cam chain guides to make sure everything is flush and seals correctly.

What is the material of choice? I've heard everything from epoxy to silicone to "the right stuff" rubber, or the non hardening stuff like "hondabond". Letting the silicone cure then cutting flush with a blade same with the rubber.

What say you?

I use the high temp copper silicon. I fill it up and assemble it wet. No need to cut the rubber plugs.
Steve

Ok, update on my situation.
the ringland on the #3 piston is cracked, and the #1 piston had the same casting number as the other 3 pistons but isn't the same. :pinch:
the domes measured .430 high on #2,3,and 4. and .350 on #1......

I gave Wiseco a call, they did a bit of digging and told me the pistons were from the mid 1990's. probably 11;1 or 12.5;1 comp.

SO, now I'm waiting on my friend who already has my cylinder block to measure the bores to see if I can stick with my 72mm bores and just order a 72mm piston set.
I already have the correct gaskets, Wiseco rings, wrist pin clips etc for 72mm Wiseco pistons that are showing up in the mail from z1 enterprises, I would just need to order the pistons and choose my compression ratio 9;1 or 10.25:1. Not wanting a race bike, I just want to ride this thing.

If I find out the bores are shot and need bored I'll need to reconsider my next move. Good times......

hey, at least I'm learning something? right? HaHa!