Kawi2strokes.com Forum

Hi Guys

I sent off my 2005 cyl and head to Eric Gorr racing to have a 295 big bore kit installed.
My stock piston has the window on the reed side but when talking to Eric he said
he doesnt put the window in his 295 kits for fear of cracking pistons. He said it will
have a more spread out power band. He also said if I had to have the window he would
cut it in but that I would be very pleased without it ! opinions ????? Moo ???

Thanks

Dave

Sounds like he is being lazy. Is it a bore or stroke job?

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

Bore to 295 and re-plate, port job, cut power valves, cut new squish.
John, he also said it didn't need the window. What would you do ??

Dave

I figure if these haven't cracked yet...
But what does the intake side look like now? Some pistons have a high arch on the skirt instead of holes or slots.

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If it surges, that's normal, upshift.

It's not stroked, so your piston speed isn't going up, I personally would put them in.

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

Can you post a pic of the old piston Dave?

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

Any idea what the measured piston to bore clearance is?

If the clearance is set to be reasonable, and not wildly loose, I'd forgo the slots and simply cut the TZ radius on the bottom of the intake side. This takes the issue of cracking/breakage of the intake side of the piston away all to together, while accomplishing the same as the slots.

Unless the lower edge of the port was radius'd/opened into the lower end, slots/TX cut IS vital to have.

Dave C sent me this. I would put the hole in personally.

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

Someone once posted the TZ750 runs backwards compared to our triples.

If so, the inlet skirt (still the aft side of the piston) is essentially unloaded during the power stroke, which allows aggressive piston cuts/holes that would cause piston failure in our engines.

Can anyone confirm the direction a TZ crank runs?

J

According the the North American 2 stroke site, the TZ 750 does rotate backwards.

But the main thing to look at is the piston pin location, The TZ pin is located low in the piston. So the piston is more stabilized in the bore as far as piston rocking goes. I wouldn't even think of doing the crescent cut out on an H series motor, the skirt would be way over loaded from the higher pin location. Plus the guys that actually have raced the Yammi twins in the last decade, found excessive damage from high cutting the crescent.

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