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andy198712
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Joined: December 05, 2010
Posts: 1209
Location: Cornwall - UK
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 Posted: Sun Mar 01, 2015 2:48 am Post subject: Broken piston rings? |
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What causes piston rings to break?
I'm stripping an old 1200 cora 60's, and on the no 1 & 2 pistons, one had the top ring in 2 parts, two had the top ring and the second ring broken in 2 and 3 parts...
ring lands aren't broken, and the tops of the pistons look OK but i need to clean them up.
No major scores in the barrel that you can feel.
one piston looks like it picked up a little on the skirt but other then that....
Any ideas?
Cheers
Andy
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Kjell Roar
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Joined: December 08, 2008
Posts: 1326
Location: Norway
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| Posted: Sun Mar 01, 2015 6:15 am Post subject: |
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Worn out cylinders/pistons do tend to break rings. You have to check the clearing between them, and see if it is too large.
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andy198712
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Joined: December 05, 2010
Posts: 1209
Location: Cornwall - UK
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| Posted: Sun Mar 01, 2015 8:56 am Post subject: |
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| Kjell Roar wrote: |
| Worn out cylinders/pistons do tend to break rings. You have to check the clearing between them, and see if it is too large. |
That's true, I was going to check the remaining rings in the cylinder and see what the gap is like,
To do the check your talking about, I don't have a bore gauge, can I just slip feeler gauges between the piston and barrel? Top or bottom?
Cheers
Andy
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Kjell Roar
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andy198712
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Joined: December 05, 2010
Posts: 1209
Location: Cornwall - UK
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| Posted: Sun Mar 01, 2015 3:53 pm Post subject: |
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| Kjell Roar wrote: |
| Not the best way to do it. Ovality of cylinders can also be an issue when worn. |
Hadn't thought of ovaling... Hmmmm!
Tbh this is just to tide me over for a few months so I don't have to rush my 2110...
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andy198712
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Location: Cornwall - UK
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| Posted: Thu Mar 05, 2015 1:27 pm Post subject: |
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well i measured the ring side clearance in the pistons, some second rings checked out under the wear limit, but some of the top ones were easily twice the wear limit (0.12mm was it? and they were .25mm) so there a no go sadly 
i have some late 1200 pistons if they'd be the same? the ones who'd barrels fit in the 90mm case openings?
Also i foolishly broke a corner off the oil pump removing it do i need a small hole pump to match the case or can i use a later big hole one? which i have one spare but was worried about cavitation
Cheers
Andy
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| Alstrup wrote: |
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mark tucker
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Location: SHALIMAR ,FLORIDA
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| Posted: Fri Mar 13, 2015 10:38 am Post subject: |
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| most of the time broken rings are detonation and or leen condition,over heat. and some if there is a ridge on cylinder and a bearing startes to go the ring contacts the ridge and breaks. but mostly detonation/over heat/leen |
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andy198712
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Joined: December 05, 2010
Posts: 1209
Location: Cornwall - UK
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| Posted: Sun Mar 15, 2015 4:13 am Post subject: |
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| mark tucker wrote: |
| most of the time broken rings are detonation and or leen condition,over heat. and some if there is a ridge on cylinder and a bearing startes to go the ring contacts the ridge and breaks. but mostly detonation/over heat/leen |
chambers didn't look too lean but may have been, think one head was leaking slightly (evidence at the barrel to seal join)
either way i'm going to see if my late 1200 pistons will work with this  same pin size
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