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Discussion Starter #1
1) Just out of curiosity, on a stock bore 929, are there higher compression pistons available without changing bore. And if so, what is the prep for the cylinder walls as well as what type of characteristics would come along with this.
2) I understand you can install a 954 head gasket on the 929 and if so, has anyone done this and if so what notice did you see in performance. Also if the calculations were made, what did it bring the compression ratio up to?

thanks, Bob
 

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1) Just out of curiosity, on a stock bore 929, are there higher compression pistons available without changing bore. And if so, what is the prep for the cylinder walls as well as what type of characteristics would come along with this.
2) I understand you can install a 954 head gasket on the 929 and if so, has anyone done this and if so what notice did you see in performance. Also if the calculations were made, what did it bring the compression ratio up to?

thanks, Bob

Of course. Wiseco list a 13.2:1 piston and I'm sure others do them as well. A light hone is all you need. Expect more heat than power.
Yes, the heads and gaskets are the same pattern. I would expect _lower_ compression, not higher. The bigger bore size of the gasket would add volume. Are the 929 and 954 gaskets different thicknesses?
 

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Discussion Starter #3
I was told the 954's are thinner thus increasing compression. Never bought the two and measured though.
Thanks
 

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I was told the 954's are thinner thus increasing compression. Never bought the two and measured though.
Thanks

I haven't measured the thickness of the gaskets either.
The tiny increase in compression the 954 (11.5:1) has over the 929 (11.3:1) is probably just down to the 1mm bigger bore. A larger bore area under the same combustion chamber has a larger squish area (basically where the piston is almost touching the combustion chamber - no combustion occurs in this area) around the outer edge which increases compression. I've just pushed one of my engines out from 73mm bore to 90mm bore which makes a huge squish area around the combustion chamber so I need to do a lot of chamber work on it.
 

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I would change out the headgasket for a thinner one.. but I wouldnt go for higher compression pistons.

With that being said, take the head off and take it in to get port and polish. Then degree the cams or get race spec cams.

Friends race bike.. that alone got him 10hp.
 

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I would change out the headgasket for a thinner one.. but I wouldnt go for higher compression pistons.

With that being said, take the head off and take it in to get port and polish. Then degree the cams or get race spec cams.

Friends race bike.. that alone got him 10hp.


I agree, unless the engine is coming apart anyway the expense of replacing the pistons doesn't make it very good bang for buck.
Which part of the port/polish and cams got him the 10hp on its own?
 

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I was told the 954's are thinner thus increasing compression. Never bought the two and measured though.
I would think the 929 and 954 gaskets would be the same thickness just different bore :idunno:

I measured my 954 gasket and it is .024-.026"

Can anyone measure a used 929 gasket?
 

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I agree, unless the engine is coming apart anyway the expense of replacing the pistons doesn't make it very good bang for buck.
Which part of the port/polish and cams got him the 10hp on its own?

It went from 108hp with full exhaust and PCV to 118hp. so I guess you can say it added to it, but really 10 hp from that is nice.

It was an R6 I will admit, but still I cant imagine the 929 being a hell of a lot different in gains.
 

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It went from 108hp with full exhaust and PCV to 118hp. so I guess you can say it added to it, but really 10 hp from that is nice.

It was an R6 I will admit, but still I cant imagine the 929 being a hell of a lot different in gains.

So port/polish _and_ cams got 10% improvement?
 

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How much thinner would you go?

You need to measure your piston-to-valve clearance and work from that.
I took 0.55mm out of my '98 GSXR750 by splitting the head gasket and removing the base gasket with no problems at all.
I took 1mm out of my Suzuki Swift car engines with no problems as well.
 

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Discussion Starter #12
You need to measure your piston-to-valve clearance and work from that.
I took 0.55mm out of my '98 GSXR750 by splitting the head gasket and removing the base gasket with no problems at all.
I took 1mm out of my Suzuki Swift car engines with no problems as well.
Suzuki Swift?
 

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Discussion Starter #13
I agree, unless the engine is coming apart anyway the expense of replacing the pistons doesn't make it very good bang for buck.
Which part of the port/polish and cams got him the 10hp on its own?
To lazy to get out the manual, but briefly what is involved.
Thanks
 

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To lazy to get out the manual, but briefly what is involved.
Thanks

To replace the pistons?
A _complete_ engine teardown.
 
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