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I ran a ported head on my race bike and it threw a cam chain, so I replaced the head with a standard one, valves were done and same cams put back in. The power was down. Not much but noticeable.
 

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Noticable by your butt dyno, or lap times. If your an Expert level rider a significant change will show in lap times.

All moot for me as my race org had a simple rule to keep costs down. "no metal may be removed form the engine internals.
A few exceptions were a 3 angle valve grind only and small amounts fro balance purposed.
They even tried to ding me for elongating the cam chain sprockets for decreeing the cams.
BTW I found the stock settings (cams) produced the most area (power) under the curve. albeit a 2 hp loss from some more aggressive settings.
But for my home track Loudon. best pull out of the corners at 6000 RPM was critical.

FOG
 

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It was never on the dyno, definitely the butt dyno. Was running megacycle cams, 38mm flat slides, raised compression, ported head, supertrapp 2 into one and methanol fuel. This was in the early nineties so I can’t remember what l had the lobe centres dialed in at. The racing class here was open so you could do anything you wanted. the 500 was always a better bike out of the corners and top speed than the 400 4s but the chassis suspension, wheels and brakes were no match.
 

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Discussion Starter #24
Interesting approach kiwigpz! It is in the same line as I did with two other bikes. I also reshaped the valve seats as shown below. The exhaust port will be widening from the valve seat up to the end of the port, so the hot exhaust gasses can keep expanding without building up pressure.
Besides the seats and ports, I removed every hump of material between the valves in the combustion chamber. This will probably feel as a contradiction because this step will lower the compression ratio. But in the earlier posted diagrams from the before and after dyno run, a 14% gain in torque over the full rpm range is visible. Also, the oil temperature dropped 10^C. In my Moto Guzzi the oil temperature even dropped 20^C.
I'm really curious to what this approach will do for the EX / GPZ!

 

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you missed some tricks. if your looking to get max power.
1 Re cut the seats to get the maximun diameter the seat inserts will allow then cut the seat width to 1/16 use a larger valve if you need too cutting the valves does little.
Run valve clearance as low a .005 (recheck often)
Porting without a flow bench is really guess work and can backfire and things like laminar flow and turbulence cannot be determined.
I have found little more than cleaning of the worst carbuncles is all. rough cast surfaces actually flow better than polished
 

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Discussion Starter #27
I'm not looking for more peak power. Hopefully the modifications wil actually make the power delivery more manageable and with that save the crank. With the EX, it will not only the exhaust that will be ported, but I'll make the intake ports also smaller in according to the Moto Man USA method.
 
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