piston to cylinder clearance

[Ron Klippenstein]

What is the recommended piston to cylinder wall clearance for a 1958 R60 ? Is it the same as all R60's up into the /2s?

[Jon Kent]

Have you got an original BMW manual?(The one in about 4 languages?) That shows the clearance in the list of engine specs somewhere. I can't remember itt myself-all I know is my R69S must have loose clearances cos it uses oil!

[Gerry Douglas-Sherwood]

Hi Ron,

BMW state the piston skirt clearance as 0.05 - 0.06mm for R50/ 60 models, 0.08 for the R50S and 0.08 - 0.09 for R69S models.

In a suppliment for the US models no alteration to those figures is given.

Gerry

[Daniel A.]

Equally important are the end-gap clearance of each piston ring. What are the recommended clearances and at what ambient temperature is it supposed to be measured?

[Gerry Douglas-Sherwood]

Piston ring gap should be between 0.25 -0.40mm on all models.

No specific temperature is mentioned, probably as the gap is so big normal ambient temperature is sufficient.

[Ian MacDonald]

Have been on Holiday and only just logged on to see recent messages. The BMW workshop manual Page 25 gives piston skirt clearances for rebore purposes. A normal ( non Sidecar ) R50 andR60 needs 0.05 +0.01 mm. I have just rebored my R50 to that specification and all is well.

[Jim]

Be careful here. Are these old pistons or new? My old R69S pistons (Nov. 1973 manufacture) need .08mm clearance, but my new KS pistons from Mark, for R69S and my Dad's R60/2, are marked for .05mm clearance.

I was a little puzzled by the large reduction in clearance on my R69S, but Mark just confirmed this by telephone.

Jim