Kawi2strokes.com Forum

As I posted, there wasn't a lot of skirt left with the accidental huge test slots. And holes are for street bikes.....

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

After checking the latest template that you sent me John, I realized the hole is mid way thru the slot... I'll definitely have my top end off this winter to elongate the holes I have now.
At the very least, slot them toward the rings.

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http://kawatriple.com/wtf/

You can print my photo above, scale it to H1 size, and use that for the template. Or for even better performance, don't scale it down.

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If it surges, that's normal, upshift.

Yes it is Andrew, 1/2 the hole is open at BDC for flow to the boosts, and about 1/2 are open when the the skirt bottom is starting to uncover the intake port.

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

just curious, but how much gain is there in HP (dyno, not seat-of-pants), by slotting instead of the holes? Seems a set of 4 holes would be much stronger.

and if HP gain is minimal, is that extra <1% worth the potential fail when running hard?

finally, on modern engines that are reeded from the factory. (MX and Snowmobile) Is it possible that these pistons are designed with a slightly thicker intake skirt to compensate for missing material of slots/holes? Has anybody ever measured skirt thickness of a sled or mx piston to check? and compare to the Wiseco or Wossner piston-port pistons available for our bikes?

I'm thinking that a piston designed for use in a piston-port engine doesn't like having its intake skirt messed with. Heck, we all know how easy it is to collapse a Forged Piston skirt.... I've folded a few over myself.

one more thing...

I believe that I read on the old board that all size Wiseco H1 and H2 pistons are from the same "mold"..
After the piston is made, they are then machined down to each specific size.

So, the larger the bore, the thicker the skirt as less material has been removed during the machining process.

Stock Bore + Wiseco + Slots = ticking time bomb

No idea how Wossners are made.

Not in the least. Now huge slots, that different......

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

Just mind the web between the slot and transfer cutout. The 500 cutout looks fine to me.

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http://kawatriple.com/wtf/

What are you trying to say, Andrew?

I'm going to have the cylinders off and will inspect my pistons for cracks sometime soon. They've taken a couple good overrevs and are still going though.

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If it surges, that's normal, upshift.

I have built 4 H1's with cylinder reeds over the years, as well as 4 H2's. I use a piston cut like the 1970's Yamaha TZ750 OW31, NO rear skirt at all, and have had NO issues with those piston cuts in the Kawasaki engines at all. I have also done a whole bunch of those mods for TZ700/750 top ends on both RD350 and RD400 with spacer plates. 350 becomes a 373, 400, 423. I kept the bore clearance to .0015, no issues.

Some would say that the thrust on the TZ700/750 is different than the TZ/RD twins and Kawasaki triples, and they are right for the most part. TZ700/750 cranks spin backwards in the cases, but, RD/TZ twins and Kawasaki spin forward. TZ700/750 thrust is on the exhaust side of the piston on the power stroke, which has a full skirt, Twins and triples are on the intake side, but that hasn't seemed to be an issue.

With no inlet skirt, it can't break off and fall into the engine.

Look up the piston for a Yamaha TZ750, 1977 or so OW31 Replica. that's the ones I used in the different Yamaha twins, and cut my Kawasaki cylinder reed valve'd pistons to.