Piston Boost Port

[best]

You Guys are fast!!!!!

Are you kidding?
Joe, Neil and I have been talking about this for a couple months!
Just had to get all fired up excited about it to do it in a flash.

Awk, this made a change on the scale of a different pipe, airbox lid off, or planing the head. Noticeable. Worthwhile.
Not earth shattering, but distinctly a gain.

How it works in conjunction with Boyesens is another question.

Steve

 

[Blaaster]

That piston is wicked, I hope it holds together long enuff to finalise the tests.

 

[joeak47]

What a cool test! I just about fell out of my chair when I saw how big you made the "EXTRA LARGE" boost port in the second round of tests. I was like >

Now when you google the question...

does a yamaha blaster piston boost port work?
You get an actual answer,with test results,showing the outcome. Not a bunch of opinions, Obi Wan Kenobi gobble dee goop,theories,or guesses,etc. just facts from an actual test. Imagine that.

This has been a fun test. Whats next?

I almost forgot...I predicted the outcome pretty close.

 

[joeak47]

Now about making making one of those right bend pipes...

 

[N8tsNastyBlasty]

I used to port my piston windows larger and those motors ran strong. then i wasted a piston in a matter of minutes when i went too big, took previous owners word that it fit and didnt measure the bore wich ended up being 1mm of difference ... ive noticed on several larger displacement engines that the intake windows and boysens are larger while the ports in the piston are smaller than the blasters.i gathered that the design emphasis was on flow after the piston cleared the intake window. I dont doubt it made a difference in performance. i like cast pistons just fine but i dont know how ur piston port will impact piston life as the bore wears and the piston slaps a lil bit. I like the diy mod and see style of it for sure !!! sharing knowledge of first hand accounts is priceless IMO

 

[Paulie B]

This is only my opinion but that piston is traveling so fast I doubt the windows make a difference. Any differences felt if any is likely due to the piston being lighter- maybe they help on the low-end when piston travel is slower.
Back when Yamaha had 2 versions of the same motor the Wood/trail version of that motor had the widows on the piston while the MX version (YZ) did not.

 

[best]

This is only my opinion but that piston is traveling so fast I doubt the windows make a difference. Any differences felt if any is likely due to the piston being lighter- maybe they help on the low-end when piston travel is slower.
Back when Yamaha had 2 versions of the same motor the Wood/trail version of that motor had the widows on the piston while the MX version (YZ) did not.

These motor have their heritage in piston port (no reed valve) and as such work wonderful without the windows and reed valve. Higher top end power is actually possible.

Well, there is no doubt the piston boost port made a difference, not huge but more of a difference than a +4 timing or airbox lid off does on the machines where they help. I have run light pistons before (on KTM 125 mind you) and this is a larger effect than that. Paulie, I was skeptical too, but I could feel the change the first time and increase again the second.

That piston is still in the engine at the moment, free time and snow are limiting our ability to get it out to switch over the top end to Joe's at the moment. The goal is to switch over when we can ride old setup - switch - ride Joe's cylinder so we can compare. Currently about 6"-8" of snow down, have to wait until there is less than 4".

Any suggestions you'd like to see us try on the boost port piston before we pull if off?
Even larger port, stuffed pin, crown cut-out on the exhaust or transfers?
Now is the time to try, this fine running piston is going to trash, let's use it for testing...

Steve

 

[N8tsNastyBlasty]

I have shaved down the pistons slightly on the exhaust side to advance the timing, saw it on the namura pistons,. I also like to take the hard *90 angle off the crown circumference, gasses hate sharp edges ,
That's all I got for piston mods .....