Piston-cylinder clearance?
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Tourer
Joined: Jul 2007
Posts: 497
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From: New Egypt, NJ
Piston-cylinder clearance?
Piston installation instructions give "nominal" clearance figures, with the disclaimer that "final sizing needs to be made based on your conditions" taking into account components used, climatic conditions, fuel, compression, etc.
This information isn't all that helpful unless there's some reference. This pistons in question are Keith Black low expansion forged pistons, 4032 alloy. Nominal clearance is 0.003" followed by the disclaimer.
So, what clearance is generally accepted for a street engine in a heavy bike running 10:5 or perhaps slightly higher, up to 10:7, compression? The bike lives in the northeast but gets ridden all over, year round.
This information isn't all that helpful unless there's some reference. This pistons in question are Keith Black low expansion forged pistons, 4032 alloy. Nominal clearance is 0.003" followed by the disclaimer.
So, what clearance is generally accepted for a street engine in a heavy bike running 10:5 or perhaps slightly higher, up to 10:7, compression? The bike lives in the northeast but gets ridden all over, year round.
HDF Community Team
Joined: Jun 2006
Posts: 12,780
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From: san antonio
.002" to .0025" for forged; not sure what "low expansion" means but that would seem to indicate that low expansion pistons could be set up tighter than .003". You know what they say about KB pistons? KB = Ka Boom.
I have never run any KB pistons but JE, CP and MTC forged and all setup between .002" and .0025". Forged pistons, after break in, wull typically rattle when cold but quiet down once heated up and expanded.
Cast pistons can be set up much tighter but are not available in the larger bore sizes.
I have never run any KB pistons but JE, CP and MTC forged and all setup between .002" and .0025". Forged pistons, after break in, wull typically rattle when cold but quiet down once heated up and expanded.
Cast pistons can be set up much tighter but are not available in the larger bore sizes.
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Tourer
Joined: Jul 2007
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From: New Egypt, NJ
"Ka Boom"? That's funny! I'm running a set right now and don't have any issues but am going to be taking the top end off and thoroughly checking things, "cc-ing" and getting the heads machined to increase compression, as we discussed at length in a previous thread some time back.
HDF Community Team
Joined: Jun 2006
Posts: 12,780
Likes: 2,609
From: san antonio
"Ka Boom"? That's funny! I'm running a set right now and don't have any issues but am going to be taking the top end off and thoroughly checking things, "cc-ing" and getting the heads machined to increase compression, as we discussed at length in a previous thread some time back.
Good luck.
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Tourer
Joined: Jul 2007
Posts: 497
Likes: 8
From: New Egypt, NJ
Thx. Have done a recent compression test, 180 psi in both cylinders. Will do a leakdown test as well. Hadn't thought about the torque plates, but you're 100% right. I can get my hands on a set of those.
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