Yamaha 62T/61X Displacement vs. Bore/Stroke Combinations

[Vumad]

That chart doesn't work for me anymore!
Piston bores are way too small!

I want chuckie to do naughty things to my motor. I'm sure he want's to get paid though... =(

 

[fatboyktm]

I asked Ada the same thing about the 760 domes they told me i a superjet pump gas would be fine. But not for the Blaster.

 

[Fro Diesel]

I run my 760 at 200psi. 33 cc domes. Pump gas only. But no one said this was a good idea...

Sent from Fro Diesel using Tapatalk

 

[Quinc]

I thought this was going to list power output between cc. With all other things being equal how much more power would you get out of a 718 vs 701 or a 754 vs 771?

 

[smoofers]

I thought this was going to list power output between cc. With all other things being equal how much more power would you get out of a 718 vs 701 or a 754 vs 771?

There are so many variables to consider. When you look at flow of the motor and scavenging characteristics of the exhaust vs bore size etc. Each setup will essentially be different from the other, its apples to oranges.

 

[Quinc]

How about a 701 fully tuned, bpipe, dual carbs, porting, prop etc vs a 754 that is also fully tuned and running the same compression type of porting and prop. How much more power would the extra 53cc's in the 754 give you? 10hp? 25hp? Also would you get anymore power with bore vs stroke to get that extra 54cc?

 

[Matt_E]

Sure. Pick a number and run with it.


Edit for a serious answer: Pick up a mechanical engineering/thermodynamics textbook, and look up the chapters on heat cycles. I don't remember a lot, but the power output is determined by volume of air/fuel, temperature of a/f mix before compression and after ignition. So basically you are picking up a little bit of extra power through the bigger volume of air/fuel

 

[kevbo]

How about a 701 fully tuned, bpipe, dual carbs, porting, prop etc vs a 754 that is also fully tuned and running the same compression type of porting and prop. How much more power would the extra 53cc's in the 754 give you? 10hp? 25hp? Also would you get anymore power with bore vs stroke to get that extra 54cc?

Well, if you have 7% greater displacement and everything else is the same. What do you expect? At least read the old Gordon Jennings book, it is probably floating around the net. Tuned pipes complicate everything so there's a lot to learn.