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I measured the cylinder bores and pistons last night and wanted to post the results and get some feed back. I can not find a specified cylinder - Piston clearance spec in the manual but my interpretation is that it should be about .002" - .0025". It would appear that my piston/bores are stock.

It's tough to put this in a table so I did something a little different that follows what the manual shows. The three measurements in A/B are Top, Middle, Bottom.

What I'm trying to determine is if I would be save just honing the cylinders and installing new rings. The manual calls for a a min piston size of 2.754" but what does the experience of the mechanics say?

 

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MNellis said:
..... I can not find a specified cylinder - Piston clearance spec in the manual but my interpretation is that it should be about .002" - .0025". It would appear that my piston/bores are stock......
What I'm trying to determine is if I would be save just honing the cylinders and installing new rings. The manual calls for a a min piston size of 2.754" but what does the experience of the mechanics say?
I'd just give it a good honing and run with it.
You save big bucks - probably $40 per hole for boring, then the cost of new pistons/rings (probably $100 at least).
The measurements aren't perfect, but not bad.
The range you mentioned for piston cylinder clearance is ok. No spec for that anywhere to be found in any Honda manual.
 

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Where did you measure pistons?
About 8~10mm from bottom at 90 degrees to pin?
Its weird you have cylinders wider in non-thrust area (sides) at middle point
Not sure I would run it with that clearance, I've seen what happens when a piston breaks up.
PJ
 

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I agree with Bill, while it's not perfect it should still give you lots of miles without trouble with those clearances. Mine had .0055" and .006" clearances and I decided to go oversize but if it had been like yours I would have just honed it lightly and replaced the rings.
 

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crazypj said:
Its weird you have cylinders wider in non-thrust area (sides) at middle point
Not sure I would run it with that clearance, I've seen what happens when a piston breaks up.
PJ
I thought the taper was a little weird too, but wrote it off to measuring error. That last digit is pretty much in question, except with really good equipment.
 

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Discussion Starter #6
tbpmusic said:
crazypj said:
Its weird you have cylinders wider in non-thrust area (sides) at middle point
Not sure I would run it with that clearance, I've seen what happens when a piston breaks up.
PJ
I thought the taper was a little weird too, but wrote it off to measuring error. That last digit is pretty much in question, except with really good equipment.
I agree with you, especially with the 4th digit. My dial bore guage reads in .0005" inc so the "in between" reading are an estimate.

I took the readings last night after a long day. Even on a good day with two experienced machinists, I've seen guy read differently by up to .001". I was going to take the reading again and I'm sure I'll come up with slight differences....everyone uses a different 'feel' and I have done much of this since the mid 80's.

Back in the day when I was building my own race car and bike motors (only a few of them actually) if I recall correctly, we would never run a new motor closer than .002 piston to wall. Typically, it would be more in the .003 - .0035. They didn't have to last more than a season though (and frequently they didn't) ;).
 
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