Valve seat inserts (Dura-Bond)

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

Leaking carburetor screw caps

When the screw caps on the underside of the carburetor keep leaking (after having installed new gasket rings), then the probable cause is the condition of the seat of the carburetor gasket. If you look closely, you will probably notice that the surface is rough, damaged or scratched. The solution is NOT to further tighten the screw cap: the gasket ring is not flexible enough to fill these small damages. The seats of the gasket rings can be machined, but if the damages are not too deep they can be removed by sanding the seat with a very fine grit
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Crankcase surface repair

By Michel Loos, The Netherlands The photos are self-explanatory. Steps:  filing  – sanding – pneumatic hammer – aluminum oxide blasting (Edelkorund) – glass bead blasting  

Instructions for Cylinder black (Einbrennlack)

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

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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Carburetor reconditioning

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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Fuel tank repair

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.  

R24 crankcase repair

By Richard Sheckler –  Wayne, Ohio. An R24 brought back. Scroll down for Richard’s story.         I met Garfield Smith (Petrolia, Ontario) more than twenty years ago. He mentioned that he had an R24 BMW which was made during his birth year 1949. This was also an important year for BMW, because they were in serious financial straights after WWII with the shackles of the Allied Military Command mandate not to manufacture motorcycles that could be used for making war. In 1949, the restrictions were lifted partially, allowing German firms to build motorcycles up to but not
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Carburetors

Overview of carburetor nr’s and settings