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The table below shows the radial clearance specifications for all bearings used on the R24 – R69S models

A comprehensive list of special and generic tools

Based on a sample of 74 gear sets, this graph shows the frequency of the different gear sets and the spread around the target dimension of +0.

  Click thumbnail to open the list. R24 – R27           R51/3 – R68           R50 – R69S            

The front main crankshaft bearing is enclosed in the bearing bushing (P/N 11 11 0 002 156) by the front main bearing flange cover (P/N 11 11 0 002 176) and a spacer ring (P/N 11 21 0 016 244), to prevent axial movement of the crankshaft. If you notice that the 6207 bearing still has some movement in the bushing, it is usually caused by a worn main bearing flange: the edge of the flange has bent back over the years and therefore no longer has enough height (+- 4 mm) to enclose the bearing. With the correct pressing tool, the
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Some rubber parts are still provided with a (wax) layer when shipped: a mold release agent. A cleaning solution with hot dish soap and water is enough to remove this layer. Use rubbing alcohol for stubborn stickiness. Although alcohol is an effective cleaner for most kinds of stickiness, you should only use this cleaning agent on rubber occasionally. Dampen a clean rag with alcohol and wipe at sticky areas until they are removed. Rinse the rubber with water afterwards. Exposing rubber too often or too long to alcohol may cause it to break down more quickly than normal.

A “strenght & weakness” overview of the different seal materials available in the market.

Very informative video! https://fb.watch/gQycYmmz_h/    

The BMW specification for the radial clearance of the conrod big end & crankpin is based on the use of slightly spherical rollers in some of the crankshafts. The use of spherical rollers prevents the rollers from “biting” when the crankshaft flexes at high RPM. Today the new FAG Dürkopp conrod sets are equipped with cylindrical rollers. This requires a slightly larger radial clearance to prevent the rollers from getting stuck when the crankshaft flexes at high RPM. Spherical rollers (used) are identified by the wear track in the center of the roller:                
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If the valve adjusting screws have reached their end and there is still insufficient valve clearance, the cause may be (a combination of): the valves sit too deep in the valve seats the cylinder head sleeves have sunk deeper into the cylinder head over time. In our experience, the sleeves at the exhaust side sit usually deeper than at the intake side. Below an example of 2 R27 cylinder heads. The RHS sleeve at the intake side of cylinder head 1 has a height of 88.47 mm The LHS sleeve at the exhaust side of cylinder head 2 has a
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This video shows the repair of the idle mix thread: a thin alu-bronze bush of M8 / M7 x 0.75 is installed in the carburettor, realizing a very wear-resistant and strong thread Click this image to watch the video on Youtube:  

In this video a method is shown to remove the old and install new tappet guide bushings from a 2 cylinder engine. The new bushings with an outer diameter of 24.97 mm have an interference fit with the crankcase. After installation, the bushings ID needs to be reamed / honed to give a tappet clearance of 0.02 – 0.04 mm Click this image to watch the video on Youtube:                    

The drive shaft flange has a press fit with the shaft. A workshop press is needed to press the flange off and onto the shaft. When removing the flange, standard press plates can be used to support the flange. However, to press the flange back on, the drive shaft collar must be supported. There are several ways to do this, but this tool works best for us. The tapered shape of the 2 halves and the ring ensures that the shaft is increasingly clamped during pressing. The edge of the hole between the 2 halves follows the radius of the
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The number stamped in the crankcase (from -10 to +10) refers to the size of the crankshaft and camshaft gears installed by the BMW factory. After 60 – 70 years of service, the crankcase may have grown, which means that the original gear set may not be the optimal set anymore (0.01 to 0.02 mm play between the 2 gears). One way to determine the correct gear set number is to measure the c-t-c distance between the crankshaft and camshaft. This value must then be compared to the nominal c-t-c distance. This is impossible without very accurate measuring tools. The difference in
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  4 versions of the saddle Y-frames are available: P/N 52 51 7 002 164:   R51/2 – R68      with 8 mm holes for saddle bearing bolt 52 51 7 002 125.7 P/N 52 51 7 002 165:   R51/3 – R68      with 10 mm holes for silent block 52 51 7 002 141 P/N 52 51 7 002 115:   R25/2                 with 8 mm holes for saddle bearing bolt 52 51 7 002 125.7 P/N 52 51 7 002 116:   R25/3 – R27      with 10 mm holes for silent block 52
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Recommended press fitting for valve seat inserts in aluminum cylinder heads: OD insert 30 – 40 mm: 0.15 mm / 0.0059″ OD insert 40 – 50 mm: 0.18 mm / 0.0071″   Spindle speed for cutting a seat pocket in aluminum cylinder heads: 400 – 600 rpm It’s recommended NOT to freeze (f.i. with liquid nitrogen) the sintered valve seat inserts before installation. The valve seats are to be pressed in with a flat and square seat driver tool. The valve seat is inserted with the radius side down.   Source: DuraBond

If you are working on the overhaul of a 2 cylinder engine block with the old 1 or 2 pin breather plate, it is advisable to replace it with the later version with cast-in pins The pins of the early 1 or 2 pin breather plates are known for loosening or breaking off, causing damage to gear case cover. However, this means that the complete set of gears must be replaced (from 20° to 30° gears) The breather plate of the newer version is also available with larger slots, reducing pressure in the engine block during the downward movement of
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A frequently asked question is how to fix a leakage of the idle mixing screw. Further tightening the nut of the idle mix screw is certainly not the solution: holes have been drilled in the idle mix screw which connects the idle mix chamber to the the outside air. If fuel leaks out through the same bore, it simply means that the fuel level in the float bowl is too high. (assuming that the bike is on the center stand, if the motorcycle is placed on the side stand, there is a greater risk of leakage) If the carbs keep leaking, it’s
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By Michel Loos, The Netherlands The photos are self-explanatory. Steps:  filing  – sanding – pneumatic hammer – aluminum oxide blasting (Edelkorund) – glass bead blasting  

Cylinder black with part nr. 09122 For temperatures up to 500 °C continuous use and up to 700 °C with impact load 200 ml is sufficient for 2 to 3 large cylinders. Ideal for spraying and painting engine cylinders, exhaust systems and other metal objects subject to high heat. Classic cylinder lacquer is initially thermoplastic; in other words although it is air-drying, it becomes sticky even with moderate heat, expands and hardens again when it cools down. This process is repeated as long as the polymerization temperature is not reached. The lacquer must be heated at least once to 150-180 °C to finally cure. After
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BING jets are stamped with numbers, such as 35, 40 (idle jets) and 110, 115, 120 etc (main jets). One would expect that these numbers refer to the diameter of the jet bore, however this is not the case. This is confimed by the company BING in Germany. A few examples of main jets measured with a wire / jet gauge: BING 44-051 main jet 130 = gauge 120 (= 1.2 mm) main jet 125 = gauge 110 (= 1.1 mm) main jet 120 = gauge 105 (= 1.05 mm) main jet 110 = gauge 95 (=0.95 mm)            
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The Bing carburetors used on the R51/3 to R69S models came with 3 different flanges. We sometimes get the question: can I put carburetor X on BMW model Y? In theory you can put an R51/3 carburetor on a R69 engine and even get the engine running, but you will quickly discover that the air pipes won’t fit. These images are self explanatory   Modified carburetors can be found in the market that fit the R68, R69 and R69S cylinder heads. However, there are some differences from the original models, most notably the carburetor flange:              
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We offer the restorations manuals from Barrington Motor Works for following models (click the link): R26 – R27 R51/3 – R68  R50 – R69S   A copy of the original BMW Repair Manual R50, R60 and R69S can be downloaded here: Download            

3 different breather plates have been used on the boxer engines:

With hardly any new carburetors being produced by BING for the < 1969 BMW mono and twin motorcycles, it’s getting increasingly important to be able to repair and recondition the used original carburetors. Luckily, special parts and tools are available nowadays to restore the carburetors to a good working condition. A. Idle mix screw: very often, the M7 x 0.75 mm screw thread in the carburetor housing is worn out. There are 2 good solutions to this problem. 1. drill the threaded hole to 7.2 mm – cut M8 x 0.75 mm screw thread – install the idle mix screw with
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By Richard Sheckler, Wayne, Ohio. Spot welding of panels inside the tank for strength and to plug the rust holes. The tunnel is removed to get inside. The last step before reinstalling the tunnel is to weld the knee pad brackets in place. When the tunnel is TIG welded in place, the inside is sealed with fuel resistant epoxy.  

By Richard Sheckler –  Wayne, Ohio. Crank case repair. I was for the most part unemployed for about two years in the mid-1990’s. I had an ‘under the table’ job working on motorcycles for a friend and fellow collector. One time after some persuasive negotiating, I received payment in trade. That was a partial basket case 1953 BMW R68. The bike had matching serial numbers, to whom, if you are a collector, is regarded as significant. Karl B. a long time M/C race enthusiast and rider acquired the R68 from a family near White lake, Michigan. The bike had been
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Overview of carburetor nr’s and settings  

The photos are a compilation of the work done on different crankshafts: R67/2, R60/2 and R69S.