Gpz750 Max Piston to Cylinder clearances

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23 Oct 2010 20:38 #408646 by gpzman2000
Gpz750 Max Piston to Cylinder clearances was created by gpzman2000
Same bike as before in my other posts. '85 Gpz 750, KZ based motor , with Weisco K810 piston kit.

Right now, I am measuring the piston to cylinder clearances.
Here's what I found:

#1 = .0022 "
#2 = .0040 "
#3 = .0002 "
#4 = .0004 "

From what I've read, .0025 " is the ideal clearance.
However, I am in the process of doing a light hone and installing new rings.

My question here is, ..and based on your experiences...

Am I okay to assemble and run the engine with these clearances ?

What can I expect in the areas of compression and performance ?

The cylinder head has just been completely overhauled.

Thanks.

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  • Becker
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23 Oct 2010 23:52 #408670 by Becker
Replied by Becker on topic Gpz750 Max Piston to Cylinder clearances
Is this a new motor that you are building or was this bored out before and now you are rebuilding it??

If you're 100 percent sure those numbers are right then 3 and 4 are too tight. Who did the boring job for you?? Usually they'll ask for the pistons or supply them, and hone the cylinders to fit. If its a new motor and I were you I'd switch pistons two and three and then hone 4 to fit.

78 KZ750B3
79 KZ400 LTD
78 KZ650C2
79 KZ650C3
78 KZ650B2A
80 KZ650F1
80 KZ650E1
81 CB750K Super Sport

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24 Oct 2010 00:09 #408672 by APE Jay
Replied by APE Jay on topic Gpz750 Max Piston to Cylinder clearances
.0015 is ideal for that kit. .004 will have piston rock.

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26 Oct 2010 20:44 - 26 Oct 2010 20:45 #409311 by nads.com
Replied by nads.com on topic Gpz750 Max Piston to Cylinder clearances
I knew Long Noung was right when he said if the pistons are 2 loose, no power. More than one machinest did not want to set clearance at .0015 for me, saying that's too
tight for an air cooled motor. I don't run them lean so it really doesn't matter. I figure it'll either seize or it won't. Now heres an example of clearance at .0015 and it seems that it's "ok" to run it like that. And wouldn't you know it's an air cooled motor too. :huh:
Last edit: 26 Oct 2010 20:45 by nads.com.

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