Calculating Head Squish Measurements - (REP)

[ossagp]

I wouldnt get too warm and fuzzy about that original Genesis design. I am not sure that Yamaha would have had to patent the original one to keep it from being copied. There was a lot about the FZ750 to make it desireable, but from what I keep calling the garage tuner or builders standpoint, there was a good reason that other designs were more desireable. In a nutshell, any engine that required you to run advances as high as mid 40's (ignition advance in degrees before TDC) was not a particularly good design. Compressing gasses that are expanding is not considered desireable (a horrible waste of energy in my opinion). Yamaha changed that, kept the amount of valves and kept the name. But that original chamber design is probably safe for the ages.

With all that you know about overlap and how compression ratios are figured, I guess you were just testing us with that question about 2 strokes and 4 strokes weren't you?

[2kHondaCR500R]

Wow! Great info guys!

[Tdub]

As far as the Genesis engine design, ever wonder why Rossi's MotoGP Yamaha only has FOUR valves per cylinder?? One way to make a 5 valve YZF achieve the same HP as a 4 valve CRF? Make the YZF a 4 valve head! LOL Tdub

[ossagp]

So did you get that 4 valve working on the blue rig? I noticed last year that Yam's new 4 valved 3 cylinder snowmachine engine is called,,,,(what else) a "Genisis". Interesting chamber on it and it works well.

[Kels]

I have some tech articles on my website that discuss these issues .

They are located at RK Tek 2-Stroke Heads: Technical Articles if you wish to have a look

Kelsey

[E-man811]

Welcome to ATM.

You do have some great articles on your sight. Thanks for putting that out their for people. It would benefit most people to go read them.

If I may offer some feedback to Kelsey... I couldn't get past some of the terminology discrepancies. Small albeit, but significant enough to cause confusion in someone who is learning. i.e. One of your articlea is spot on about the importance of measuring and knowing the relationship between the top of the piston at TDC and the top of the cylinder. But your article refers to this as "Piston Deck Height" which as your article moves on, abbreviates to "Deck Height". This relationship of the Piston to the Deck is called "Piston Deck Clearance" or "Deck Clearance". But describing this incorrectly as "Deck Height" will certainly lead to confusion for a few people as they try to learn more about building engines.

"Deck Height" is the distance from the centerline of the crank to the top of the cylinder. "Deck clearance" is Deck Height minus Stroke + Rod length + piston compression height +/- variances = where the top edge of teh piston will stop at the top of the stroke.

To Kelsey... Don't mean to nitpick, it's just a peeve of mine. I welcome them back also.

To everyone else go read Kelsey's articles

Ride safe

Ian

[Kels]

I appreciate the feedback..

You are correct.. By me abbreviating "Piston Deck Height" to "Deck Height" .. I can see how it could take on a diffrent meaning to those 4 stroke engine builders..

I do believe that piston deck height is a clear and correct term and is also known as piston deck clearance.. While deck height by itself could relate to block deck height..

Thanks for pointing that out.. I will modify my article..

Kelsey

[hellhound]

wow,thats awesome information thankyou so much for takeing the time to write that.i wish i could just bring lots of my stuff in but i wont get into all the reasons why i dont.i really think you and doggers posts are the best i have read so far.iam still not done yet lots to go.