Kawi2strokes.com Forum

Are the dimensions in the Denco Porting Specs table http://kawatriple.com/portdencospecs.html measured from the existing deck height or after being machined for correct squish?

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We don't need no stinkin' Cams!

The dimensions are measured from the top of an untouched cylinder.

(I have what appears to be a pic of an original Denco document. The stock port heights are listed for the S3, H1, and H2 on top of their respective model columns. The kaw manual confirms the stock dimensions listed for the H1 and H2).

J

Actually the heights are for zero deck, straight from Tony.........

And I put that Denco chart together years ago. (the one with stock specs)

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

The Denco chart I have (which includes the stock port heights) states the h1 exhaust port to be 35.4mm. I just measured both a late model and early model stock H1 cylinder. 35.4mm it is......

Threepipes'. Shoot me a pm with your regular addy and I'll fwd the table I refer...

J

This is the chart I made.

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

It would appear this chart has corrected numbers to reflect port heights measured from the stock deck/head gasket height.

IE: The H1 70hp spec requires a 1.6mm exhaust port lift and the 75hp spec requires a 2mm exhaust port raise. These numbers appear correct....

J

believe what you want Scott, I'll tell Tony you said he is wrong...........

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

As I interpret this chart, the dimensions are based on stock deck height. For example, the H1's intake port stock dimensions are listed as 65.4 x 41 mm, and for all tuning stages the intake port is listed as STOCK i.e. unchanged. Ditto for the 70 and 75 HP tuning transfers which retain STOCK dimensions i.e. 48.8 mm from top of cylinder. Finally, the chart does not specify that the cylinders have to be zeroed- surely that would have been mentioned if it were necessary?

Re the 90 HP 500, the porting specs are much milder than those of the H1-RA, for which KHI claimed a power output of 82 HP at 9,500 rpm. Has anybody actually tested this 90 HP setup on a dyno? Same applies to the 75 HP specs which are milder than the H1-R's which also produced 75 HP at 9,000 rpm.

Could someone explain the difference?? I dont get it top of cylinder is top of deck which is zero???
I really need some 2stroke learning........

It's not a 2-stroke thing. The top edge of the piston at TDC defines the top of stroke as far as the ports are concerned, since that's the part that covers and uncovers them. The actual top of the cylinder was typically somewhat higher than that, so the distance from the top of an unmodified cylinder to a port is different from the distance from the piston edge to the same port. Since port timing and measurements are usually calculated from the top or bottom of the stroke, using the top of the cylinder can result in wrong port dimensions. When getting the heads properly shaped for correct "squish", etc., the first step is normally to deck, or cut the top of the cylinders to match the stop of the stroke. Otherwise you would have difficulty getting a 1mm squish, for example.

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If it surges, that's normal, upshift.