Source for R 50/5 pistons and rings

[Tinkertimejeff]

Anybody have a suggestion on where to get new or very good condition 1970 R 50/5 piston and ring sets? I just got my early (tin foil ID tag) and I may want to redo the top end completely.

[schrader7032]

Would an option be to go oversize to an R60/5? The stroke is the same, just the bore being bigger. If the 500cc parts are rare, maybe the 600cc stuff is more available?

[Tinkertimejeff]

Thank you responding so quickly Kurt. If I can't get the 500 cc pistons I need I would consider going to 600 cc. I do have a question about that upgrade. Would I have to get another set of cylinders or could I get away with boring out the stock 500 cc ones. One side could be used as is 69.97 piston but the other side is stuck with some rust so it will need a oversize and I would like to keep them equal.

[schrader7032]

I think the issue with going oversize or to 600cc is how much steel liner is there. The 500cc is 67mm bore while the 600cc is 73.5mm bore. So you would need to take out around 3mm of thickness. Seems like a lot but you can see the steel liner with the jugs off. I faced the issue on my R100/7 when I needed to do a top end. The 1000cc jugs are basically right at their limit...I had read that going one oversize for them was risky as the remaining liner might deform or get wavy over time. So I opted for an aftermarket kit to replace everything.

Maybe others have experience with the 500/600 jugs to know better. Maybe the better thing to do is to find 600 jugs and pistons and hold back your original jugs for later on.

[cbclemmens]

Jeff:

Have you tried Max BMW (maxbmw.com)? They had rings and head gaskets for my R75/5. They list new pistons and jugs on their parts fiche and I have had good luck getting parts from them. They also list an engine upgrade kit for the R50/5, with oversize pistons and jugs to increase engine size up to 1,000 cc for something like $1,200. (your old heads will fit).

You could also try euromotoelectrics.com. They mostly have electronic parts but I have gotten other stuff from them as well.

I'm not sure of this, but I think the jugs for the R50, R60 and R75 are the same casting with different size bores. You might check that also.


Craig

[cbclemmens]

[Tinkertimejeff]

Craig, I contacted MAX the other day about the cylinders and pistons on the web-site, I'm waiting to hear back to see if they have any information on the availability for the parts. I have found, even if its listed it does not mean the parts are available anymore. I still have options, my search to find a decent set of OEM parts has just begun. It took 5 years to get the stuff I needed for the 505 restoration and 13 years for the Police Green '55 R 50. It's out there somewhere I know.

[r67boxer]

Motorworks in the UK may have a pair:

https://www.motorworks.co.uk/catalogsea ... -1973--232

I've purchased many parts both new and used and have always been satisfied with their service.

Kevin

[Tinkertimejeff]

I am confident that I have secured a very nice set of R 50/5 cylinders for this restoration. Thank you all for the responses.