2 stroke head grooving...

[moto_psycho]

Anyone tried it? Found an example on this page http://richstaylordporting.com I need to reduce my compression a little and am wondering if this is worth a try...?

[OLHILLBILLY]

I dunno, first time I've seen that one. Looks kinda sketchy to me. Why do you want to reduce the compression?

[moto_psycho]

I machined for squish clearance and was borderline too high. Fine on the mx track but ran with ignition off in the woods ?

[JoeRC51]

Put two base gaskets on it and leave the head alone.

[moto_psycho]

Found it on this site also

http://www.dicksracing.com/motorcycle_performance/4-stroke

Head gasket is o-rings. And I'm a machinist ?

[JoeRC51]

Base gasket = cylinder gasket. And you're no mechanic.

[moto_psycho]

1.5mm stack to align ports at TDC thus i don't want to alter port timing. And im afraid i am but as with most information regarding 2 strokes, it is fractal and open to interpretation, hence i am asking for opinions and hopefully somebody with a bit of knowledge and experience will share their wisdom.

Not you apparently...

[Wild Alaskan]

I'm sure grooving it would work, doubt there is any advantage vs making the bowl a little deeper though

[JoeRC51]

1.5mm stack to align ports at TDC thus i don't want to alter port timing. And im afraid i am but as with most information regarding 2 strokes, it is fractal and open to interpretation, hence i am asking for opinions and hopefully somebody with a bit of knowledge and experience will share their wisdom.

Not you apparently...

 

The altered port timing would be an additional benefit.

[moto_psycho]

Its already done. Can you please respond to the original question. I can either machine the combustion chamber or put grooves in to reduce the compression, seems there's a possibility I may gain more low/mid doing so.

[highmarker]

This mod comes and goes through the years and is not predictable in it's effect, consider it an irreversible experiment. Removing any material would lower compression ratio though. 

[76xtdrvr]

Assuming it was the head that you already skimmed...... If it was mine, I'd do some creative Dremel work and  hand polish for a smooth blend within the squish area. You probably have to do trial and error compression checks to get what you want anyway. Much easier to Dremel out a little at a time, and "sneak up" on the desired compression than to do multiple machining setups, or risk removing too much material on your 1st machining pass.

[moto_psycho]

Worse case cylinder heads are relatively cheap to replace, I'm still hunting for reviews of heads people have machined, but the theory appears sound. Though I do wonder about the effects on piston cooling and whether it negates the benefits of a squish type combustion chamber

[76xtdrvr]

Those little ball-mill grooves machined in the head look like a place for some carbon buildup over a short period of time. Just my opinion.

[slotracer577]

The whole point of the squish band is to compress and move the charge to the center. Adding grooves only gives an area where the change won't move to the center.

I have not messed with 2-st in a long time, but I do remember that if the squish velocity gets too high you get detonation. So the width of the squish as well as clearance is important.

Edited November 13, 2016 by slotracer577

[moto_psycho]

In one of the classic 2 stroke tuning books it also states the squish benefits cooling by providing a layer of cool gas around the periphery of the piston. I wonder if these grooves negate it by allowing the flame front to travel up them and ignite this layer sooner?

[William1]

Please post in the model appropriate section.

Thanks!!

[Wild Alaskan]

And how was this make model specific? Its a general two-stroke head question...

[highmarker]

Mod would be in use by every auto and engine manufacturer if it increased combustion efficiency. It's nothing new. 

[kxrob]

when you do squish you machine dome as well . 

you want to push the charge to the center but don't want high compression that causes detination and reduces over rev