BA
Pro
Posts: 1592
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posted January 05, 2004 06:29 PM
Another 1270 vs 1290 question!!
So, the 1270's seem to have a 13.5 CR, but the 1287 JE kit comes with a 13.0 CR. (Muzzy and Wiseco have the 1270/1272.
Am I going to be able to get in the 13.5 CR range with a 1287 or 1290 kit? (maybe removing the head gasket shim?)
Will this possibly put me in a bad range of possible piston/valve contact??
Thanks!!
  
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ninja12
Needs a job
Posts: 3310
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posted January 05, 2004 08:14 PM
do you mean base gasket or removing a layer of the head gasket?
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BA
Pro
Posts: 1592
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posted January 05, 2004 08:27 PM
fuck, I don't know. 
Whatever part people have been removing!! I really don't know! Please tell me! :-p
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BA
Pro
Posts: 1592
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posted January 06, 2004 01:02 PM
Got this from MTC today. WOW!!
quote:
What compression ratio do I end up with when I use your 1290 'Pro-lite' kit for the Kawasaki ZX-12R?? My friends are telling me that I get about a 13.5-1 Compression ratio when going with a +2.5mm (1270cc) but that the 1290cc is only a 13.0-1 ratio.
If they are right, I'm not sure whether I'm better off with the lower cc's and higher compression, or the higher cc's and LOWER compression.
Thanks,
Allan
-----------------------------------------------------
-----Original Message-----
From: MTCPiston@aol.com [mailto:MTCPiston@aol.com]
Sent: Tuesday, January 06, 2004 1:34 PM
To: BA
Subject: Re: zx12pistons
Our pistons are 14.5 to 15: 1 in the 86 mm
Gina
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psycho1122
Pro
Posts: 1608
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posted January 07, 2004 06:18 AM
The 12r engine in the sub 1300cc class responds MORE to compression than the cc's, not to say that some extra cc's is not good. How to go about maximizing CR w/ your kit was covered in the "Other" thread.
The Muzzy kit is the way to go......the thin slipper rings yield more power due to less friction.
I would question the CR claim by MTC. Never heard or seen such pistons.
____________
You say PSYCHO like it's a BAD thing!!
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BA
Pro
Posts: 1592
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posted January 07, 2004 07:07 AM
Yeah, I was thinking that their CR claim was a bit ridiculous but I needed someone who knew better to set me straight.
Thanks Psych.
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted January 07, 2004 09:19 AM
psycho,
The MTC's are "Pro Stock" style pistons, very light. The compression is possible with proper set up.
One small correction. It's not really correct to refer to the thinner rings as "slipper" style. The word "slipper" refers to a style of piston which does not include a skirt around the full circumference of the piston. Both styles are common, although a full skirt is more common in a cast piston. The thinner rings, correctly, reduce friction and resist flutter. Other than the part number coding and size there is no name for them.
Here's a thought about the difference between a 1270 and 1290 cylinder size-When determining the strength of a cylinder, the radius of the cylinder is a multiplier in the equation. A small change in radius multiplied against a large pressure results in a significant change in total stress. It is not an insignificant number.
Anecdotal proof- I learned early on when building the ZX-11's that apples to apples, a 1080 (77 mm bore) always made more power than an 1109 (78mm bore). The reason was that the extra mm of bore allowed the cylinder to flex, go out of round under pressure. Externally this condition manifests itself by the almost universally present cylinder blowby in high compression 1109 ZX-11's, and conversely the almost universally dry 1080's.
Every parameter in an engine has an ideal size or value. Go beyond these and performance is reduced rather than increased.
Doug
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justoyz2
Zone Head
Justoyz Racing
Posts: 858
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posted January 07, 2004 09:56 AM
well spoken Doug, thanks for the tech tip
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psycho1122
Pro
Posts: 1608
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posted January 07, 2004 10:20 AM
THX for the correction on the use of the term..."slipper" Doug.
____________
You say PSYCHO like it's a BAD thing!!
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k bryant
Needs a job
Sponsor
Posts: 2911
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posted January 07, 2004 10:37 AM
 Edited By: k bryant on 7 Jan 2004 10:38
We use to run 2 ring Slipper Pistons in the 70's/80's on our Yosh engines in roadracing. Worked great, just didn't last very long. For awhile, we all got on the "Mahle" piston band wagon. They were really expensive, but lasted longer and nice quality.
Never have relied on the piston compression # as gospel. Just a baseline. Your combustion chamber final shape, how far you let the piston go into it, how much you flycut for valve relief, etc, etc, plays a role in how much your final compression ratio ends up being.
We had some engines with the pistons sticking up out of the cylinders. I use to think that was kinda "out there". Closest we'd ever get on piston to valve/head was .040. Seemed like if you missed a shift in those days, you might as well pull in because the valves would be bent from over-rev.
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BA
Pro
Posts: 1592
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posted January 07, 2004 02:24 PM
that's awesome anecdotal info about the ZX11 Doug.
it begs the obvious question though, which I'll go ahead and step out on the plank and ask now....
(You may have your hands tied on how you can answer this, but please let me know if that is the case.)
Is there any data to suggest that the 1290cc kit for the ZX-12R might suffer the same situation as the 1109cc ZX-11??
If your personal thoughts are 'tied', is there a Muzzy standpoint about the subject, or should I consider the Muzzy 1317 kit as my answer? 
( I think that puppy is going to be cost prohibitive for me but it does make me drool)
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Outlaw1
Zone Head
Posts: 803
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posted January 11, 2004 08:44 AM
Edited By: Outlaw1 on 11 Jan 2004 08:45
BA the way I read this the higer compression of a 1287 kit could/would be prone to losing pressure and going out of round. This may be the reason Muzzys has the 1270 kit.
And if NOS was introduced into 1287 kit, I get the picture 
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addisonzx12
Expert Class
Posts: 213
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posted January 11, 2004 08:56 AM
I think, but am not 100% sure that Coby Adams & Bob Carpenter 12 engines use the 1290 configuration. I don't think they would use it, if it had problems!
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RobMuzzy
Expert Class
Posts: 295
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posted January 11, 2004 09:43 AM
The official MUZZY stand is. We tested with many combinations including 86mm and concluded that the 1270 configuration was best.
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psycho1122
Pro
Posts: 1608
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posted January 11, 2004 08:49 PM
____________
You say PSYCHO like it's a BAD thing!!
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