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There Be Singles PDF Print E-mail
Written by BMWVMCA NEWS   
Tuesday, 29 July 2008

THERE BE SINGLES: Black Painted Heads & Valve Covers           

Sometime during mid-production of the R25/3, the engineers at BMW were made aware that there was a serious problem with overheating and piston seizure with their latest model single.           

Part of the immediate fix was to hand out a free half pint can of lead based black enamel paint and a brush to each R25/3 owner who came into BMW dealerships. The instructions were to paint the head, valve covers and oil pan. The engineers believed every bit of heat transfer from the engine to the atmosphere would help.           

When an R25/3 came in for service, the timing was retarded from 7 degrees to 5 degrees BTDC.           

When the shop techs adjusted the valves as part of a ‘tune-up’, they replaced the valve cover gasket with one made of aluminum.            

New R25/3s now had these changes incorporated into their manufacture. Beginning with bike #260322, the ignition timing was changed to 5 degrees BTDC. At #261301, the carb main jet was changed from 105 to 110. With #263051, the heads and valve covers were painted matt black.               

The changes helped, but they were not enough. With the introduction of the R26, the new front fender (mudguard) no longer had its fancy mud deflecting flare, which meant more cooling air would reach the cooling fins. The area of the cooling fins on the head and cylinder were increased by 60%. The engineers also added direct lubrication to the piston skirt, described in the next section. 

 

Last Updated ( Tuesday, 29 July 2008 )
 
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