Bridgestone Motorcycle Parts Discussion Board
Bridgestone Tech Talk => 350 Talk => Topic started by: MitchB on July 03, 2015, 06:16:13 PM
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Is there right way / wrong way to install piston rings?
I've carefully looked at a new set (STD), and there is a small marking on one near the gap. My gut tells me that it goes in the top groove, facing up...
I've looked through notes I've collected and this site and the service manual. No mention of fitting the rings...
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There is only one size of ring for the 350 GTR/O, yes have the mark at the top.
Z
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Yikes, i did not know this....dn't know if mine are correctly installed now :-\ What happens if the rings are opposite the way they should be? ( top ring on bottm / bottom ring on the top grooves on the piston ). I am very worried now as this could affect something when i did have it running last year for about 5 minutes total time...hmmm ..scared at the thought now. bsforever
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I'm now concerned too. I am about to put mine back together and have been clueless about this little nuance. Can someone please articulate what the marks look like, where to find them, and how to orient the top and bottom ring? In the past I have assembled motors with no regard to this requirement and not had any (to my knowledge) issues. :o I just keep learning little tricks from this group. Thanks and please educate me.
...bert
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On the rings I received - bought on eBay from Richard's - there is a very tiny marking near the gap on one side. It's not easy to see - more of a embossed mark than a stamping. On one set, the mark was visible on only one ring - on the other set it was visible on both rings.
I have memories of 2-stroke rings needing to be correctly installed to insure the rings "scrape" correctly. Thus my request for clarification. Some, maybe not all, have a slight bevel where they contact the cylinder wall.
Stupid me, after just sliding the rings into the cylinder from the bottom I rotated the piston to verify the gap was correctly set on the piston I must have caught the top ring on the open part of the cylinder - and it snapped. One broken ring.
I didn't force it - I was surprised how little force it took.
So I'm waiting for an expert to weigh in too.
Now there are no rings avail on eBay. Guess I'll send Richard a note to see if any are avail.
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Hi, Mitch.
The markings should be fairly easy to see on the top face of a new ring, close to the ring ends. Once the ring has been used, ring movement tends to rub out these markings, so you will probably not see them on a used ring. The marking is probably "NPR", standing for "Nippon Piston Ring" who manufactured them. On the cast iron barrelled motors, the oversize will be shown on the opposite ring end as "50" for +0.5mm, "100" for +1.00mm and no number to indicate a standard bore ring. Of course, no such marking will appear on 90 Sport, 175, 200 or 350 rings.
On rings for alloy cylinders (90 Sport, 175, 200 and 350) both rings are identical, so there is no specific "top" or "bottom" ring. Just fir the rings with the marking uppermost. The 50 and 90 iron-barrelled motors had a chrome plated top ring, easy to distinguish on a new ring by its silver colour, where the cast iron bottom ring is black. Not so easy to tell on used ring, as both end up polished and shiny silver!
I think the idea of a "right way up" for rings originated where the ring is not symmetrical. Some have a taper on one face (i.e. they are keystone shaped in cross section) and if one of these is fitted upside down, you won't able able to compress the ring fully in its groove to fit the cylinder.
Cheers,
Graham