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Discussion Starter #1
I have a CB350 twin which I want to install a pair of good 66-67mm O.E. type cast pistons that'll give me a 10.5:1 compression ratio. Have any of you found anything that'll work as a direct swap after boring it out ? I was told a KZ750 piston may work... ?
Thanks for any ideas.
 

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XR200, 350 block needs modifying
 

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Discussion Starter #3 (Edited)
Hi PJ,
The CB350 twin crancases need modifying ? or the cylinder block ? Is it possible to use the stock CB350 cylinder liners w/ XR200 pistons ?Then directly bore out & ride ?

Thanks again pj,
B.
 

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You have to cut (mill) the shoulder down on the xr200 pistons.
 

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Discussion Starter #6
mlinder,
The shoulder of the XR200 piston that you're referring to,is it the area directly underneath the piston pin(the side skirt of the piston)that needs some piston material removed ? lets say so that the piston can continue all the way down to BDC and clear the crank wheels ??
have you done this mod yourself ?,
Thanks,
grcamna4
 

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No, the shoulder. The top edge of the pistons.
 

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Discussion Starter #10
drgonzo,
Can you tell me how many different mod. procedures you had to accomplish to get her on the road ? Was it a street cafe bike w/ low enough compression to run regular ? What compression ratio do you think it had ? Love to hear more...
 

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How low is the compression compared to say a Wiseco 67mm piston or a stock 64mm?
Didn't measure exactly, but small maths looked to be over 10, maybe higher.
 

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You need to hunt down a piston then do some measurements
 

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if you are going to do a retrofit like this you need to get some learning in ,invest in some measuring equipment, learn yourself about cr's ,the maths and measuring trapped volumes,squish bands, piston to valve clearances cam timing etc the list goes on
 

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Discussion Starter #15
Yeah,
I need to get the "homework" done... I'll be learning on this thread from whoever will teach me.

Thanks guys !
 

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apparently the kz400 piston and maybe kz440 pistons fit as well.
i've been going through the same search over the last few days, and i think i've decided to just use the wiseco pistons. for me, any extra machining needed on the pistons will quickly cause any cost benefit to be lost unless i can do it myself. also at least they still seem to be making rings for them.

i have seen on the internet during the search that subaru wrx 5.5mm valves are a 1mm increase on stock intake valves. i don't know how well they work with the cam though without modifications
 

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Yeah,
I need to get the "homework" done... I'll be learning on this thread from whoever will teach me.

Thanks guys !

Cant learn this on the web.
thats what machine shops are for
 

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I've built a couple of engines with the KZ pistons, they give you a slight bump in compression, the biggest benefit is the larger diameter put you around a true 350cc. & the price!!!
No piston machining required, just the cylinder bore.

Marc
 

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drgonzo,
Can you tell me how many different mod. procedures you had to accomplish to get her on the road ? Was it a street cafe bike w/ low enough compression to run regular ? What compression ratio do you think it had ? Love to hear more...
Sorry for the delay. As best I remember I made no mods to the combustion chamber and just clayed it to check clearances. Never did CC the head and calculate compression. It ran fine on pump 93.
 
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