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Author Topic: ARGH! Broken ring  (Read 2206 times)

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Offline clarkjh

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ARGH! Broken ring
« on: February 05, 2006, 11:09:52 AM »
Started cleaning up my 550 parts so that everything is nice and clean for putting it back together.  I just noticed one piston has the secound ring broke, it scored the cyclidor and jammed the oil rings.  So the question is - do I try and reuse the piston or just buy a new one, I know I will have to have the jugs done and will go with to the .25 over size rings.  Also the tops of the pistons are pitted, so if I buy one should I buy 4?

Thanks

James
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Offline heffay

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Re: ARGH! Broken ring
« Reply #1 on: February 05, 2006, 11:12:40 AM »
we want pictures  :)
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Offline clarkjh

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Re: ARGH! Broken ring
« Reply #2 on: February 05, 2006, 11:39:20 AM »
heffay, just because you asked ;D

Just couldn't get a pic of the top to be in focus :-[

James
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Offline Gordon

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Re: ARGH! Broken ring
« Reply #3 on: February 05, 2006, 11:54:55 AM »
If it were me, I would go with four new pistons.  You want all four cylinders/combustion chamber components worn equally or not at all.
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Offline clarkjh

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Re: ARGH! Broken ring
« Reply #4 on: February 05, 2006, 01:37:26 PM »
there are a set of .25 oversize rings on ebay, and I plan on having all 4 jugs done to the same spec.  Thats why I wanted to know if the piston is salvageable, then I would know if I should get the rings or order oversize pistons.  I don't want to have to open this engine for another 30,000 miles. ;)

James
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Offline MRieck

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Re: ARGH! Broken ring
« Reply #5 on: February 05, 2006, 02:17:40 PM »
Quote from: gordon on February 05, 2006, 11:54:55 AM
If it were me, I would go with four new pistons.  You want all four cylinders/combustion chamber components worn equally or not at all.
I agree. Why go through all the trouble and money on gaskets etc only to be disappointed.
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Offline TwoTired

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Re: ARGH! Broken ring
« Reply #6 on: February 05, 2006, 02:39:31 PM »
Quote from: clarkjh on February 05, 2006, 11:09:52 AM
I just noticed one piston has the secound ring broke, it scored the cyclidor and jammed the oil rings.  So the question is - do I try and reuse the piston or just buy a new one, I know I will have to have the jugs done and will go with to the .25 over size rings.  Also the tops of the pistons are pitted, so if I buy one should I buy 4?

Thanks

James

How deep is the wall scored?  I thought scored walls mandated boring them to the next oversize that clears the scoring depth.
If you bore the cylinders to eliminate the wall scoring, the existing pistons will no longer fit.  New pistons / rings go along with a bore job.
But, get your pistons and rings first and have the cylinders bored to match them.

Cheers,



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Offline clarkjh

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Re: ARGH! Broken ring
« Reply #7 on: February 05, 2006, 03:13:11 PM »
Would 650 pistons work? A few extra CCs couldn't hurt. ;D

TT, I don't think the scoring is over .25, also other then the scoring on the #4 cyclinder they are well within the standard specs.  One of the reasons I was thinking I should be able to do the .25 oversize.

James

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Offline TwoTired

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Re: ARGH! Broken ring
« Reply #8 on: February 05, 2006, 04:01:39 PM »
I just looked up the numbers in the Honda manual.  Unless, I've made a serious blunder...

The standard cylinder to piston clearance is .01 -.04 mm;  .02 to .03mm being average.

The piston service limit for wear is .25mm.
If you manage to find a "largest tolerance" NEW piston and cylinder bored .25mm over, you will be .26mm
If you manage to find a "smallest tolerance" NEW piston and cylinder bored .25mm over, you will be .29mm
The former is right at service limit and the later is beyond service limits.

Your current piston is worn how much?  Is it still round?  Do you still want to use it?

Of course, you can put it together that way and it will run.  Might smoke a bit, though.

Perhaps my math is wrong?

Good luck!
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Offline clarkjh

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Re: ARGH! Broken ring
« Reply #9 on: February 05, 2006, 04:07:53 PM »
Looks more and more like new pistons, should do the valves and guides as well.  Here's another question, will CB650 valve fit the 500 head?

James
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1974 CB550, 40000 Miles
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*** Why, oh why, is it always head gaskets with me?***

Offline KB02

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Re: ARGH! Broken ring
« Reply #10 on: February 06, 2006, 05:24:39 AM »
My opinion would be to bore it and new pistons. In just seems like it would make better sence for the long haul (as well as better compression... I could be wrong).

I also could be wrong about the valve, but I wouldn't think you could get the 650 valves to work without some MAJOR work to the head.  I'm not thinking it's impossible, just WAY beyond my skill level.  ;D
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Offline bryanj

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Re: ARGH! Broken ring
« Reply #11 on: February 06, 2006, 06:36:36 AM »
You CAN NOT put oversize rings on std pistons whith a deep hone. Cheapest way is a 555cc kit for a 500 from ebay its 0.5mm oversize for a 550
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Offline clarkjh

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Re: ARGH! Broken ring
« Reply #12 on: February 06, 2006, 08:46:30 AM »
Quote from: bryanj on February 06, 2006, 06:36:36 AM
You CAN NOT put oversize rings on std pistons whith a deep hone. Cheapest way is a 555cc kit for a 500 from ebay its 0.5mm oversize for a 550

Who has these kits, just checked with the local Honda dealer and the pistons are discontinued.  Also dropped the jugs off at a machine shop and he said it needs to be bored as just honing wouldn't get all of the scar.  Maybe I need a K8 ;) or even better a sandcast ;D.  Time to do some more digging.

James
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SOHC/4 #3328
SOHC/4 Gallery: http://www.sohc4.us/gallery/v/members/personal/clarkjh/
1974 CB550, 40000 Miles
1980 GL1100, 102789 KM - Back on the road after a complete engine rebuild. 
*** Why, oh why, is it always head gaskets with me?***

Offline Gordon

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Re: ARGH! Broken ring
« Reply #13 on: February 06, 2006, 08:55:13 AM »
They used to come up on ebay fairly regularly.  I haven't seen them lately, but then I haven't been looking much either.
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