Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: UKROBK7 on June 30, 2011, 04:22:03 PM
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Just bought 4 sets of OEM rings from Dave Silvers. They are NPR (Nippon Piston Ring Co). In each set there is ring that has a bright edge and a ring that looks to be plain cast iron. The bright edge one has a "1N" mark stamped on it and feels slightly rounded (no sharp edges). Am I correct in thinking the bright edge one is the No1 (compression) ring and should be installed with the marking facing the top, the plain ring would then be the No.2 ring?
Anyone had any experience? I can't find any info on the NPR site and am waiting a reply from D.S.
Rob
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Hi Rob, many years ago I asked about piston ring markings on the US site, here's the answers that I got.
http://forums.sohc4.net/index.php?topic=14205.msg139736#msg139736 (http://forums.sohc4.net/index.php?topic=14205.msg139736#msg139736)
Cheers
Den
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Just had the reply from D.S, it confirms what I thought! :-
The rings should be installed onto the piston thus;
The thick ring with the silver/grey edging and the "1N" marking goes on top. The "1N" mark faces upwards. As a general rule, any writing on rings always face upwards.
The thick black ring goes second.
The remaining 3 rings form the oil scraper which goes at the bottom, the 2 thin rings sandwich the serrated ring.
So away I go!!
Rob
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Just had the reply from D.S, it confirms what I thought! :-
The rings should be installed onto the piston thus;
The thick ring with the silver/grey edging and the "1N" marking goes on top. The "1N" mark faces upwards. As a general rule, any writing on rings always face upwards.
The thick black ring goes second.
The remaining 3 rings form the oil scraper which goes at the bottom, the 2 thin rings sandwich the serrated ring.
So away I go!!
Rob
Just remember that if there is a ridge on the top of the bore then standard rings can get broken if you don't hone it off, normally you would fit ridge dodgers, they have a recess cut out the top of the ring to miss the wear ridge. It will run but the first time you give it wellie the rings will break.
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In 30+ years the only Honda i ever found with a wear ridge was a PF(I think) 50 ($ stroke) with 90+ thousand on it
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Mine has no wear ridge even after 35000 miles and ovality that's well within spec. Must admit all the other aircooled engines that I have opened up have had the ridge but they weren't Honda, Honda are great!
Rob
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Mine has no wear ridge even after 35000 miles and ovality that's well within spec. Must admit all the other aircooled engines that I have opened up have had the ridge but they weren't Honda, Honda are great!
Rob
Only ever worked on two honda engines, my c50, first bike, bent a valve and set of piston rings, and my 250, rebore, camshaft and fingers, they were shit in the 70s. My mate had a 500 twin and even out the showroom it sounded like it was gona have a catastrophic engine and gearbox failure. It lasted a year and did in a gear and the camshaft, total shit, wasn't even nice to ride.
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you won't be wantin one of those then will ya :P
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Just had the reply from D.S, it confirms what I thought! :-
The rings should be installed onto the piston thus;
The thick ring with the silver/grey edging and the "1N" marking goes on top. The "1N" mark faces upwards. As a general rule, any writing on rings always face upwards.
The thick black ring goes second.
The remaining 3 rings form the oil scraper which goes at the bottom, the 2 thin rings sandwich the serrated ring.
So away I go!!
Rob
Just remember that if there is a ridge on the top of the bore then standard rings can get broken if you don't hone it off, normally you would fit ridge dodgers, they have a recess cut out the top of the ring to miss the wear ridge. It will run but the first time you give it wellie the rings will break.
Never heard of ridge dodgers, infact that sounds more like an april fools joke LOL, if i had such a ridge at the top of my cylinders i would regard it as time for a rebore and next size piston and rings
Pete
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::) "ring dodgers "sounds like some bloke who would never be seen dead in a gay bar :-*
seriously though Mr Honda started out making piston rings so i think he was pretty much clued up in that department ,so i would have too agree that Honda internals are better than anything else about at the time. i have never known Honda's too burn oil, except past the valve guide oil seals ;)
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RD rings are a common thing in the car world, made by Hepolite and Cord. Never seen any in the bike world tho'
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Not that I have done it and it sounds bodgy but some old guy told me he fitted an extra base gasket to avoid rings hitting any ridge :)
We must abuse our bikes more 'up north' Bryan as I have seen lots of barrels with a wear ridge on Hondas - mainly 250's though
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As far as i am concerned Hondas wear as much as any jap manufacturers, i have a couple of sets of 750 barrels with wear ridges which i have aquired over time
Pete