Piston ring source

[photorider]

Last night, after a few too many "sodas" I broke the oil ring on one of my pistons while doing the top end.
I ordered the rings a while back as a set. That is the only way I could find them (as a set). I would like to finish the job and don't want to have to purchase and wait for a whole new set.
Question: Is it possible to buy just one piston ring from a local shop (auto?) or does BMW use special rings that need to come from BMW motorcycle parts sources?

 

[169993]

Ring source

I doubt you are going to find just an oil ring anywhere. Even if an auto suppy had the correct rings (very unlikely), they are going to sell them as a set. When I say set, if the rings for servicing a six cylinder would fit your bike, then you would have to buy all six. The only place where you might find just the oil ring would be a dealer who has had a mechanic break some other ring from a set and has an oil ring laying on the parts shelf, again not a very likely scenario.

Purchase a good quality ring spreader before you attempt this again. It will cost less than a new set of rings. When you say you bought another set of rings, I woud think it was for two pistons...Did you break two oil rings? Not to be critical, but that would make me believe you would be better off to have someone with experience install them on the piston for you. When it comes to piston rings, most have chamfers on either the inside or outside of the ring...Sometimes these chamfers are very hard to see with the naked eye, and if a ring were substituted that had the chamfer in the wrong place, then serious damage would quickly result to both the cylinder and piston when the engine was started.

Every bike I have ever serviced has a chamfer on the bottom of the cylinder that makes installing the cyl over the piston possible without the use of a ring compressor....If your cylinders have been bored to a large oversize, the chamfer is likely to be mostly gone and a compressor will be needed. I've always used a toothbrush handle to install the piston by using it to compress the rings one at a time as the jug is placed over the rings...If you try this, under no circumstances use a metal tool such as a screwdriver to do this. Be sure to stagger the ring gaps per manual specs, and watch that they do not change as you are installing the cylinder.

Sorry I could not offer a better solution.

 

[crazydrummerdude]

Looks like they used to sell them individually, but most are "NA."

For example, for an R90/6:

http://www.maxbmwmotorcycles.com/fiche/DiagramsRight.aspx?rnd=14576174&menu=&vid=51889&Diagram=11_2140

 

[photorider]

Thanks for the input, guys. Yeah, I screwed this one up and looks like I'll have to bite the bullet and get a new set. My problem is in taking those little guys out. I can put them on pretty easily but haven't developed the technique to take them off smoothly. Last night I put the oil ring on backwards and when I took it off to re-fit it put a hairline crack it. I figured it's toast.

Thanks for the link crazydrummerdude. Yeah, it looks like they only want you to buy them as a set...

 

[robsryder]

Tools to avoid damage to piston rings

I've long had a piston ring expander and compressor set which I use on my airheads. I think (but am not 100 percent certain) that I got them from JC Whitney. I see that these tools are still available and not too expensive. The photos look exactly like those that I bought years ago.

The piston ring expander is here -
http://www.jcwhitney.com/piston-ring-expander/p2004249.jcwx?filterid=j1

The piston ring compressor set is here -
http://www.jcwhitney.com/piston-ring-compressor-set/p2004262.jcwx?filterid=j1

I've also purchased piston rings for airheads from Hastings. As I recall, I needed to speak with a nice lady in their technical department to get the necessary size (and to be certain about the orientation of each ring) -
http://www.hastingsmfg.com/

Interestingly enough, JCW also advertises Mahle piston rings and show BMW-motorcycle R bikes from the 1970s as available for $61 - [Note - I've checked more closely on the JCW website for a few of the years of airheads that I own and the website indicates that such years / models are unavailable]
http://www.jcwhitney.com/piston-ring-set/p2023324.jcwx?filterid=j1

I see on the MAXBMW website that part number 11251256473 (SET: REPAIR KIT PISTON RINGS - D=73,5), which would work on my R60/6 are only $51.15 for a set of 2 ea. so maybe the Mahle rings aren't a good deal. Elsewhere I noticed similar pricing given for each set of rings, so perhaps the 2 ea set pricing is in error.

I checked on part number 11251256477 (SET: REPAIR KIT PISTON RINGS - D=82), which would work on my R75/5 and each set are $62.57; two sets needed.

And for my 77R100RS part number 11251265505 SET: REPAIR KIT PISTON RINGS - D=94 is $62.57 EACH - two sets are needed. If one is using Nikasil cylinders it appears that the part number is 11251337399 (SET: REPAIR KIT PISTON RINGS - D=94 (to 09/80)) the price is $66.94 EACH [I'd be careful about the R100 rings - if I recall the iron cylinders used piston rings which had an outer chrome-type coating and the newer nikasil cylinders used iron rings (no chrome coating) - maybe PGlaves could chime in here].
http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51884&rnd=03192010