R65 LS Piston Rings

[DanMay]

I noticed that the early R65 piston rings are the same part number as the R75 rings

11251256477   SET: REPAIR KIT PISTON RINGS - D=82 0.09

But the later models use a number specific the R65/R65LS
11 25 1 337 401  SET: REPAIR KIT PISTON RINGS - D=82 (from 10/79)

Is this because of the Nikasil cylinders ?

[Barry]

Well the R75 never had Nikasil cylinders so it makes sense except for the date which I thought  would be later than 10/79. That would make it the 80 model year rather than 81 for the introduction of Nikasil. Anyone with an 80 that can confirm what they have ?


That's interesting and useful information for anyone with the early model.

[Tony Smith]

Is this because of the Nikasil cylinders ?

You are 1005 correct. later today I will be fitting up and filing the end gaps on a set of 1st O/S R75 rings as the barrels I'm using for my R65 are a little worn, but not enough to justify a rebore and O/S pistons just yet. I've got a nice "mix-n-match" happening. 1979/90 barrels and pistons and post 1981 heads (the left is a 1985 the right is who knows).


I suspect you also noticed that R75 rings are somewhat cheaper than r65 rings.

[Julio A.]

R65 that are 1981 models and onward use nikasil cylinders. They don't have oversized rings for those. The cylinders don't wear out, but the piston rings do.

The pre 1981 R65's had cast iron linings. The engineers from BMW may have given the R65 the same bore, but less stroke.

[Ed Miller]

We (at least on mine) use the R75 wrist pin retaining clips, too, not the later versions used on the rest of the Beemer range.

[DanMay]

So on a post '81 with Nikasil cylinders you need to use rings made specifically for Nikasil bores.  I see MotoBins has them http://www.motobins.co.uk/displayfinal.php?q=50375&topsearch=1&go=GO

  

[Tony Smith]

So on a post '81 with Nikasil cylinders you need to use rings made specifically for Nikasil bores.  I see MotoBins has them http://www.motobins.co.uk/displayfinal.php?q=50375&topsearch=1&go=GO   

You are correct. Although recently I inquired about having my damaged Nickasil bore repaired by a firm in NZ who not only do such work but restore worn iron bores by applying a Nickasil layer.
 
The price (around $500) was way too much for me to consider having the job done, good barrels can be had for less than that for a pair, even on fleaBay. But in the course of my correspondence with them I asked about rings and they basically said to use rings designed for steel/iron bores. I suspect that BMW specify softer rings simply to ensure that the rings wear and not the bore.

[bruce_launceston]

I believe it's as simple as chrome rings for a cast iron bore, iron rings in a chrome (nikasil) bore.
I put new rings in my 84LS and they were available aftermarket at not much money at all.
Sorry, can't remember the exact $.

[nhmaf]

I am with Bruce on this - one wants to use the 'hard' surface chrome rings with the iron bores (the bores slowly wear) or use the 'soft' iron rings on the hard Nikasil cylinders (which is a thin, hard coating that can't be overbored, unless the coating is removed and the cylinder is replated.