R26, 1958

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JeffR
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Joined: Sun Apr 19, 2020 10:08 am

R26, 1958

Post by JeffR »

Lapsed member of the club but found my way back. I recently bought a R26 basket case and am working to get it back on the road. Does anyone have information on creating an extra oil way in the cylinder to get improved lubrication? I think Kurt in S A mentioned it in a video post he did for this site but now I can't find it. Have the Barrington book and the four language BMW manual and neither mentions this. Does anyone have experience with doing this improvement or having it done at a shop?

The bike came with the alloy con rod and crank assembly and I found a replacement in good condition. The con rod weighs 6.60 oz. A NOS BMW piston weighs 10.80 oz. A piston from an R50S which will fit the standard R26 cylinder weighs 11.90 oz. A BMW piston from ebay which also fits the cylinder weighs 12.35 oz. Do these different weights matter? Am I overthinking this for a single cylinder machine?

Thanks in advance.
Jeff Rigby 1968 R60/2 & Dnepr sidecar, 1983 R80 ST, 1958 R26, 1968 Ducati Cafe
Jeff/Hudson NY

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schrader7032
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Joined: Fri Oct 27, 2006 3:00 am

Re: R26, 1958

Post by schrader7032 »

Welcome back, Jeff! Things have changed around here a bit!!

I am aware of a process to drill a right side oil passage on some twin cylinder models, but that's not going to help you. In the Classic Motorräder Winter of 2015, there was an article by Chris Betjemann about the oil pathways to the R26/R27 rockers. It was taken from the R26/R27 Restoration Manual that Barrington Motor Works wrote. But the article is not about drilling anything, only just describing how the oil migrates from the sump to wash the rockers in oil.

As for weights, those kind of things are somewhat foreign to me. The single cylinder bikes vibrate enough already so the idea of putting mismatched parts or parts that weigh more than OEM seems to wrong way to go. Maybe someone has some ideas...San Arthur?? Certainly Vech at Benchmark Works would have the answers.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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San Arthur
Posts: 477
Joined: Sun Apr 22, 2007 2:08 pm

Re: R26, 1958

Post by San Arthur »

Image

As you can see there is a line feeding to the head? Kurt how do you think is getting oil?
The picture belongs to ScottA and it was taken in Europe.
I show it to Perry Bushong (r.i.p.) but we never start the project.

You can find more pictures on my post:

viewtopic.php?f=7&t=10549&hilit=zenaida&start=60
San Arthur in San Antonio, Texas
'58 R26 '76 R90S '94 R100GS/PD

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schrader7032
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Joined: Fri Oct 27, 2006 3:00 am

Re: R26, 1958

Post by schrader7032 »

Clearly a racing setup where full oil flow is needed.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Captonzap
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Joined: Thu Aug 21, 2014 10:24 pm

Re: R26, 1958

Post by Captonzap »

Balancing of single cylinder engine is usually done using a percentage of the reciprocating weight mounted on the crank pin, and balanced that way.
The percentage is based on experience, read 'trial and error', and varies depending on what RPM you want the smoothest operation.
Fifty to sixty five percent is common, BSA calls for 57% for one of it's 500 singles.
BING ""balancing a single cylinder engine" and learn more than you want to know. :roll:

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schrader7032
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Re: R26, 1958

Post by schrader7032 »

I wanted to circle back to this as I discovered some notes about the engine overhaul on my R25/2. I delivered the engine to Bench Mark Works for the work. I made some notes of what they told me they were doing. One of those notes is "Drill extra oiling hole". That's all I have...I don't really know where this was done on the engine. I'd suggest touching base with them to see what it might be and if it's something that you would like to have done.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

lauffer6996
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Joined: Fri Oct 27, 2006 3:00 am

Re: R26, 1958

Post by lauffer6996 »

I remember early R26's had an alloy (aluminum) conrod, that often failed. The later R26's maybe '58 and surely '59 had a steel conrod with an appropriately balanced crankshaft. I remember reading about folks that put a steel conrod on an early crankshaft that was balanced for an alloy conrod and the bike vibrated horribly. I also recall reading about folks putting weights on an early crankshaft to balance a steel conrod. The best solution imhp is to source a late crankshaft/steel conrod combo but you might have a long search!
scott

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