Kawi2strokes.com Forum

Cliff, I posted the same question to another group and got a reply from a reliable source. He measured 106.92mm on a NOS H2B cylinder, that's 2mm taller than my shaved cylinder. Makes sense that someone was playing around with performance they might take off a relatively even number. Now to find a 2mm base gasket. I've made plenty of gaskets with a ball peen hammer before but 2mm is a little thick. I tried Cometic but their site sucks, keeps erroring when I try to register. I'll have to do it the old fashioned way and give them a call.

Dave

^ I would recommend calling Cometic. I had those same issues a couple of years ago with their website and needed a head gasket for my GT750. I called them and the representative was extremely helpful and I ordered what I needed over the phone.

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1972 Kawasaki H2 Mach IV (Candytone Blue),1984 Yamaha RZ350 (KRR- Yellow/Black), 2004 Honda Helix (Clipper Yellow).

“Jeff and Chris are THE MEN!”
RIP John E. Evans

Maybe in the resource page but, does anyone know the cyl. height on a H2?

I got a 106.92mm reluctantly.

What is reality?


cliff

Well, after a lot of hemming and hawing and advice from around the globe, I've narrowed it down to two options. I really believe the cylinder were shortened by 2mm, taken off the top. I need to bring the cylinders back up to height so the pistons won't rise above the top of the cylinder and hit the head.

I found good sources of custom 2mm gaskets, one for a replacement base gasket and another for a replacement copper head gasket. If I go with the 2mm base gasket it will throw off the timing, but I've heard some opinions that it might not be a bad thing. Or is it? I'm no exert on port timing so I have no idea.

If I go with a replacement 2mm head gasket, timing stay intact.

In both cases I'll have to measure the squish to really see where I am.

Any pros or cons for either case? Opinions wanted.

Thanks,

Dave

I don't remember... have you owned/ridden a stock H2? I like to experience a stock configuration before I modify it so I have a baseline. It's easy to try thick base gaskets along with shortening the intake side piston skirts later if you decide to.

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If it surges, that's normal, upshift.

My H2 addiction began when I bought my brothers 72 in 75. I rode it for many years before selling it. I was a poor college student in need of cash, what a mistake. It was stock but it was a hand full, always a thrill to ride. If I start with a stock base gasket and use a 2mm head gasket the bike should be close to stock (other than the oversize piston.) Then if I want to I could experiment with a 2mm base gasket and stock head gasket to see how it affects timing/performance. That's one of the benefits of a 2 stroke, easy to rebuild the top end. But it's also more of an mystery, for me, when you start playing with port timing.

Dave

The trouble with just raising the cylinder is that intake timing goes the wrong way. That's why I mentioned the cutting of the intake side piston skirt at least an equal amount.

There's plenty of 2-stroke porting information on the web if you want it to be less mysterious.

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If it surges, that's normal, upshift.

Some progress, getting closer. Thanks to Lani at CopperGaskets.us I now have .080" head gaskets installed. He does a great job, nice looking parts, fast delivery.

After putting it all back together I did a wet compression check and the readings were in the low 130s. I know this is a little low so I'm thinking of trying a new set of head gaskets for better compression. The next size down is .063" which isn't much of a difference, and then .050".
If I go with .063" I run the risk of still having low compression, if I go to .050" I might overshoot or still be low.

I measured the squish and got a reading of about .060". The heads look pretty stock so I doubt there was any machining done to them.
Does anyone know what the stock dimension is for any H2? If I know what it's supposed to be I can easily calculate the best head gasket thickness to use.

Getting closer but not there yet. Trying not to overthink.

Thanks for the replies,

Dave

You are overthinking this.