Kawi2strokes.com Forum

It never ends. I have the engine assembled (mostly) and in the frame and I starting assembling the left side. I mounted the rotor and gave it a twist to spin the crank. No plugs so no compression. But I only turned it a little bit when it hit something solid. So I turned it the other direction and (after 120 degrees) it hit again. Looking in the spark plug hole I can see this pistons topping out as I turn the crank. I pulled the head and the first thing I noticed was that the ID of the original head gasket seemed too tight, probably because the new pistons were the next oversize. But when I put it back together with a new head gasket the piston still topped out. I double checked that there was a gasket between the cylinder and the main case. So I threw a dial indicator on it and measured how far the piston went above the top of the cylinder without a gasket. I got .045". Seems like a lot to me and obviously it's a problem.

So, I have a rebuilt crank with new rods, new Wossner pistons and stock gaskets. I did not have the head, case or cylinders shaved/planed and the heads show no sign of machining.

Does anyone know where the piston should top out in relation to the top of the cylinder?

I have a number of reasons to believe the guy I bought the engine from, in Florida, was slimy and now I wonder what else he didn't tell me about this motor. When he was getting the motor ready to ship he said it was going to be expensive due to the weight so I told him to take it apart and ship it a few boxes. I know he took advantage of this and swapped out some other parts. All the internals were oily as you'd expect but the crank was dry and crusty, obviously he swapped in a bad crank. Also, he didn't include pistons and when I examined the cylinders there was some aluminum buildup on the right one, pretty sure the piston melted a little and he didn't want to send them. Did I mention the broken gear in the transmission too? Boy there are some slimy sellers out there.

Do people shave the cylinders for more compression? If so then these cylinders weren't original to this engine.

Thanks,

Dave

You can have custom size base gaskets made here: https://coppergaskets.us/

With gaskets installed, you should have around 30-40 thousandths (about 1mm) clearance between the piston at TDC and the head for the best performance. Measure carefully.

H1 deck height is +.062"(approx) or .062 thou above top ring land.
At -.045" deck .125" is shaved somewhere is my guess.

cliff

example

Seems you have some measuring to do...
This thread may give you some insight: viewtopic.php?f=2&t=7185
Be sure to read the entire thread.

_________________
Answers are here: http://kawatriple.com/

The question is where the piston is measured "above deck"
See that 65.1 measure(not yours)?
That is ref. point to deck. NOT the 68.73 measure. This is just an illustration.
Piston dome is above that.

cliff

The height of a stock H1 cylinder is 95.3 mm

case deck is 77.0mm
rod is 110
1/2 stroke is 29.35
base gasket 0.5
piston comp. hgt. 32.0(wossner (61mm)

cliff

Thanks for the replies. I placed one of the cylinders on my table saw and another cylinder form a 72 and took this picture. You can see the gap between the two red arrows showing the difference in height of the two. Definitely been planed/shaved. The problem is that it throws off the port timing, no way for me to use these jugs. Maybe someone who knows what they're doing can use them but this is well above my pay grade.

Now to find a standard set of jugs that I can have bored to fit the Wosners I have. I'm out the money I paid to have them fitted, live and learn. Anyone have a set of 74 cylinders?

Dave

PS, here's a pic showing the difference between the machined cylinders and a standard '72 cylinder. The gap between the two arrows is about .045", probably what was shaved off.

Are you sure the height removed was off the bottom?

If so, you can get a metal spacer to get it back to stock of you want.

_________________
If it surges, that's normal, upshift.

I will bet top deck shaved 1mm.

cliff