K9B/C cylinder retrofit on K9

[Matt Martin]

Has anyone been able to get a K9B or K9C cylinder on a K9/K9A?

 

I was able to bolt up the K9B, but even with the thinnest base gasket the squish was too high (~0.060″).  Given the part numbers are the same for the pistons, crank, and rods, it must be the case that’s offset just slightly to accommodate the taller cylinder.

 

In lieu of a custom piston, I was considering machining the cylinder or case to bring the squish to where it should be.  Just wondering if it’s a problem only i’m having, or if anyone else has run into this.

 

 

[William Martin]

Matt,

I have a k9b cylinder & head on my k9a engine, and have not seen this issue. Do you have the k9a head on a k9b cylinder? I don’t know, but that may be the issue you have with too much piston/head clearance. I didn’t try that combination myself…

Bill

[Matt Martin]

Bill,

 

thanks for the reply.  I have two heads, and have tried both of them, however, they’re listed as the same part number.  The only vagary is that the K9A and K9B do not show the insert as a part available separately; on the K9C parts list it is.  Homologation shows the combustion chamber as the same; so, I had assumed they’re the same.  Wouldn’t be the first time I was wrong!

 

Thanks!

[Glenn L Riggs]

I have used the b and c and kz10b on a 9 believe the cases are very close they do have different inserts for the head and make one that you can cut to meet your squish area have to watch the cc`s tho as I have had a couple that could get the squish right and have the cc would not pass so went with the rule for cc and they ran fine. Hope this helps. Have also found that when some engine builders go thru an engine they square the case and that lowers the whole thing so that may be an option also.

[Matt Martin]

Glenn, thanks!

 

I think I might end up squaring up the cases, or even looking for another case – mine is pretty beat up inside.

 

[John parker]

I have run a k9C cylinder with a BB insert in the head, the squish was tight .73mm I ran 2 base gaskets to get it to .82. The combustion chamber was 10.7cc. Great snap out of corners, good for shorter tracks but runs out of topend on longer straights. I do have to run a 50/50 C14 to pump gas mix, but I did run 20 litres of VP’s MRX02 to see how it goes,  wow, big power gains! My only fear in running a tighter squish is the rod streching during over rev and smacking the head. I put on just over 10 hours before doing the topend and have 16 hours on the bottom end, which is in need of doing now and have had no problems.

[Matt Martin]

John,

Thanks for the insight.  I ended up running my spare K9A cylinder for now.

If I can score a K9C cylinder and pipe for a deal, I’d love that.

I’m not in a rush to sort any of this out as I’m only able to get out a few times a year and run with my local club.

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