motopsycho87
New member
Has anyone had their head modded similar to the attached images? Seems a few reputable tuners do it. I suffered a bit of pre ignition with running my compression ratio so high (13.6:1) so am considering a diy job.
Squish band grooves
- Thread starter motopsycho87
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(F5)
Gold Level Site Supporter
Hahahaha. No `reputable` tuners do that.
Everyone is looking for a gimmick that can be CNCd. They do rifled spiral grooves and holes drilled from the squish to the chamber.
All that sort of stuff just increases trapped gas in a pposition it can't burn and decreases the squish effect. If you want more turbulence or max squish velocity you can do that with size of squish area and clearance. Too much isn't good anyhow.
Everyone is looking for a gimmick that can be CNCd. They do rifled spiral grooves and holes drilled from the squish to the chamber.
All that sort of stuff just increases trapped gas in a pposition it can't burn and decreases the squish effect. If you want more turbulence or max squish velocity you can do that with size of squish area and clearance. Too much isn't good anyhow.
motopsycho87
New member
motopsycho87
New member
I don't know how dicks racing managed to make his look so bad on http://www.dicksracing.com/motorcycle_performance/2-stroke_carb_mods
But mxa magazine tested a bike fitted with it in 2014 and loved it
But mxa magazine tested a bike fitted with it in 2014 and loved it
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motopsycho87
New member
Seems to start and idle well, couldn't be bothered to drain the paraffin mixed with red diesel out after measuring the volume, so my shed looks like this. Pretty much band on 12:1 now. I like pushing the boundaries, but if I can't ride in the woods without detonation then what's the point of the bike 
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...Attachments
motopsycho87
New member
(F5)
Gold Level Site Supporter
Maybe they're angled directly away from the sparkplug?.
Mxa mag probably got some stickers to play with. Or decals in the us.
Scuse my cynicism, seen this stuff all before.
motopsycho87
New member
Oh I'm skeptical too, the general consensus is more low down, less top end which seems to coincide with more squish velocity / turbulence. Apparently my mpg will go up also lol. Nothing to lose by doing it so might as well give it a try!
And it's to the plug on the up, and away from the plug on the down
I hope...
And it's to the plug on the up, and away from the plug on the down
I hope...motopsycho87
New member
I dunno, but to me it feels like the best thing I've done to my bike so far. And im a skeptic on most things! Feels like the power band bark before the valve opens now, and the over rev is actually higher than at 11.5:1 and 13:6:1. I'm sold.
pscook
Platinum Level Site Supporter
All that you did was add the grooves? Squish was already adjusted and you didn't do any modifications to the current squish?
motopsycho87
New member
Precisely. Total head volume has obviously decreased with it, but that is all. Squish was already at 1.1mm
The only way to truly quantify results is on a dyno. Same dyno, back to back runs without and with new parts. Seat of the pants impression means nothing. Placebo effect, variations in temperature, humidity, fuel, rider's mental state make it impossible to get any definitive results.
motopsycho87
New member
Oh yeah I know that. But I do ride the bike regularly, and temperatures have been pretty stable at around 5 degrees. The fact low down power feels increased with a lower compression says something. Fund the dyno rums for me and I'll do it.
Oh yeah I know that. But I do ride the bike regularly, and temperatures have been pretty stable at around 5 degrees. The fact low down power feels increased with a lower compression says something. Fund the dyno rums for me and I'll do it.
Can't do that, can't even afford to get my race bikes on the dyno.
I like to think I am pretty in tune with the bikes too, I know I felt a difference going from stock head to a cut one. Want to believe I felt something with the large volume powervalve cover, but not sure.motopsycho87
New member
There is a dyno close that does a "no appointment" day, each run is ?25 so could do one with this head and my 12:1 normal cut head with SM wheels on... More concerned with just riding it atm, the trip to work and back was awesome!
(F5)
Gold Level Site Supporter
I've spent a lot of time on the dyno (I have a tame one I can use myself) and the amount of times I've made cool changes and then tested them to find worse results that often I couldn't tell riding it.
I became quite proficient and could probably write a book on the best 40 ways to detune your 2 stroke. I came to dread dyno nights. But those special times when what you did worked were good. For some reason I'd always send other people away with decent improvements when I helped them, but my own bikes fought the hard fight. They were however usually the fastest in class.
A harsh mistress.
I became quite proficient and could probably write a book on the best 40 ways to detune your 2 stroke. I came to dread dyno nights. But those special times when what you did worked were good. For some reason I'd always send other people away with decent improvements when I helped them, but my own bikes fought the hard fight. They were however usually the fastest in class.
A harsh mistress.
motopsycho87
New member
I'd be very surprised if the bike is producing less power, it starts and runs better than it ever has, considering I've tried 11.45:1 13.6:1 and now this at 12:1 having done a replate and bottom end rebuild before trying all. I ride my bike a hell of a lot, and like you have found many things that are supposed to give power actually bitterly disappoint, normally with an associated price tag! This however, besides jetting properly, has stunned me
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