12 - 12.5 compression ratio in KZ1000P?

Hello all,

Haven't been here for quite a while, but _really_ like the new look of the site!
Anyway, on to the question:
I saw a KZ1000J cylinderblock on offer with Wiseco high-compression pistons. Compression ratio is between 12.0 - 12.5:1. The seller is a well-known Dutch go-faster merchant, and tells me that with 98 octane this will run without detonation problems. However, I searched the forum and read that the J model doesn't respond well to higher compression ratios. It does seem a bit high to me...so: what do you think? At 100 euros for the complete set (block, pistons, rings) it seems too good to pass up...or too good to be true.

Jeroen

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1982-1986 KZ1000 Police in black/no fairing
1977 Z1000A2 streetfighter
Moto Martin Z1000 in pieces

What size is the piston kit? Is the cylinder block a stock Kawasaki unit or aftermarket?

One thing to concider is how you're going to start a big block kawi with 12.5 to compression.....

You'll have to retard the timing for starting or your stock starter won't do it.

Hello Kazilla,

The block is stock Kawasaki, the pistons are normal size.

Then it's just the starting issue you have to deal with.
If you used a thicker head gasket you might be able to get the compression down to where the starter would work. You could buy an iginition controller to retard the timing but they're expensive for a street machine.
You could always have the tops of the pistons machined down so you're in the 10 to 1 compression range.
Thicker gasket is the way to go. 12.5 to 1 is too high for a street bike anyway....

Good luck

Hello Kazilla,

So a thicker head gasket would be enough to get it just working, or would it make it streetworthy (reliable) as well? Where can I get these? I didn't know there are different thicknesses, I have always ordered just by part number.
Machining would mean considerable additional cost, and because I do not know who I can trust with this in the Netherlands, I would like to avoid it.

There are many places on the Web to get thicker head gaskets. With thicker head and cylinder block (base) gaskets you should be able to get the desired CR.

I know that APE (aperaceparts.com) carries at least .43 copper head gaskets. There are also spacer that you can put under the cylinder block that will raise the cylinder there by putting the pistons lower in the sleeves and reducing compression. I sure APE carries cylinder spacer also. You can also find thicker head gasket on the Web by searching for "copper motorcycle head gaskets".
Do you have a picture of the pistons so we could see the domes?

a stronger starter would help too, isnt there a honda one that works?

Don't know about another starter that fits the KZ1000....

77KZ650 wrote:

a stronger starter would help too, isnt there a honda one that works?

Honda starter in KZ1000 thread

Lists Honda models to get the starter from, along with links.

Post edited by: steell, at: 2006/05/04 23:25

ok. this one i got to hear about. i am going to pay close attention to this subject.

now. can a 1075 with 12.5 to 1 compression be run on the street with 98 octane gas?

will this run hotter? i want the most power i can get out of my 1075 and still have it streetable or right on the edge of street and strip ( riden but riden hard 90 % pf the time)

thanks

sbjones wrote:

can a 1075 with 12.5 to 1 compression be run on the street with 98 octane gas?
you will have to carry octane boost with you if you want to fill up at a gas station
will this run hotter?
more compression=more heat I believe, just get a bigger oil cooler

You might drill a small hole through the head at each cylinder, couple each hole to a ball valve, gang the valves and have a compression release similar to the high comp thumpers.