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Home arrow VMCA Newsletters arrow Volume 2, Number 2 - April 1, 2005 arrow Fitting a Later R60/2 Crankshaft Into an R67 Case
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Written by BMWVMCA NEWS   
Tuesday, 29 July 2008

Fitting a later R60/2 crankshaft into an R67 case            

Does anyone know if it is possible to put an R60 or R60/2 crankshaft, cylinders and pistons in an earlier plunger frame case?I've discussed the idea briefly with Ed Korn and it seems possible, but I know there are "issues", the most prominent being the differing overall length of the crank and the front (and possibly rear) bearing carriers.Anyone have experience with such a conversion?areas of concern for me are the aforementioned bearing carriers, crank spacers, timing gears, front crank pin diameter, and flywheel/clutch assembly.BTW, I have my own machine shop so making up or modifying parts is within reach.Your insight, thoughts or guidance is appreciated.           

I am a professional metalworker and was hoping that you might be willing to share some of your experience in repairing that case.(R68, see issue #2 VMCA News, Ed) I am contemplating a case repair myself that is not nearly as extensive, but I think it is worth doing since the bike has matching numbers.It's an R67.            

Specifically, I was wondering what filler rod your welder used, and how you were able to simulate the original cast texture on the case after the welds had been ground.Any other tips or enlightenment would be greatly appreciated.

Kind Regards,
Donald Cope 

Hello Donald,           

Regarding the R68 case repair, there is a detailed story in the second issue of the BMW VMCA News. I can send you some information if you like. I will need your postal address.

Regarding crankshafts: I believe an R60 crank will interchange with an earlier R67 crank, and all the R67 corresponding parts will still fit into the earlier case.           

Later cylinders will interchange with earlier R67 cylinders. The pistons from the R60/2 have a higher deck height (shorter rods) than the R60 or R67 pistons. Pistons would have to be used with a matching crankshaft, unless you have the crank rebuilt using later (shorter) rods. All the later pistons use 20 mm wrist pins. I do not know whether the R67 used 18 mm or 20 mm wrist pins. BMW also went through several changes in piston design between 1951 and 1961, in that they changed from five ring to four ring to three ring pistons.            

You can also have Arias custom make pistons from forged blanks. The R67 through R60/2 tend to have low compression. With custom pistons, you could bump that up a bit. They will help you re-design your replacements.           

An R60/2 crank, I believe will fit into an R67 case, but R60/2 corresponding parts will be needed. If you have both cranks out of the cases, compare the distances from the web front and rear surfaces of both cranks.           

The corresponding parts needed to match the crank will be the timing chest cover, (either early or late), and generator armature. Pistons should be as covered above.           

The bearing carriers can be made to work. The differences in the carriers is mainly in how the inside lips fit into the oil slingers. It is best to find the oil slingers that correspond with whatever carriers you will be using.           

If in doubt about the carriers, use the carriers that correspond with the replacement crank.           

Regarding spacers: MRC and some of the other bearing outlets sell shims in 1/10th mm thick increments. They come in ‘ten packs’ and sell for a few bucks. They are an almost exact match in ID and OD for the BMW spacers. I have to use a die grinder with a sanding drum to slightly enlarge the ID on their shims. Shim the crank to center in the case. The crank is locked in place by the forward bearing acting as a thrust bearing. You will need to lock the forward carrier in place to check the spacing. With Ed Korn’s special ‘Many In One’ tools, the job is a snap.           

The rear bearing will float when the engine is up to temperature.            

Check the distances between the open faces of the slingers and the case.     

They should be close enough for oil to splash into them, but not close enough to touch anything. You can see the front slinger from the left side, and the rear slinger from the right side of the case with the jugs off. Rotate the crank while inspecting this clearance. The slingers will not be an exact fit against the crank web, because they are spun sheet metal and secured by the spacers and one screw on one side.           

This one is probably going to open a can of worms. I do not recommend use of barrel roller main bearings unless you are going to use only thin oil and run the engine only at operating temperature, and not to exceed 4500 rpm. You really can't hurt barrel roller bearings, but they can and do hurt the rear carrier and crank journals. There is so much shear resistance between the rollers and races to force the races to spin against the carrier on the outside and the crankshaft journal on the inside.           

I hope that helps.

Regards,
Richard 

Richard,

I will join.I've been meaning to but have just been too busy and distracted to do it. Now I'll have the perfect excuse to get around to it.

Kind Regards,
Don.  

Last Updated ( Tuesday, 29 July 2008 )
 
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