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Old 02-06-2014, 06:14 AM   #102
MotorcycleWriter OP
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Joined: Dec 2012
Location: World's Rockiest Trails
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Originally Posted by scootrboi View Post
I attended a Open Wrench Night at a private bike building garage, riding in on my 50s vintage scoot. There was a Britbike on the repair stand, something old with an Amal carb. I asked about the metal hoses on the outside of the cylinder. External oil lines. I mentioned my bike didn't have an oil pump. That piqued the host's interest, he is interested in how different schools of thought design motorcycles. I showed him how the oil vapor was delivered to the valve levers by removing the oil cap and feeling the air pumping out. There are little points molded into the inside of the cylinder head cover that drip the condensed lubricant onto the bushings. The oil is distributed by the crankshaft that splashes oil around. This may sound primitive, but it is part of an old formula for reliability. No oil pump, no tiny passageways, no moving parts except the already moving crankshaft. The engine doesn't turn very fast, and ignition points last many years, and are simple to set. This simplicity and formactive design makes diagnosis of a problem so elementary that even I can do it. The valves have a single angle, the last time I burned a valve I lapped in a new one, no machining. The pushrods need no attention. The final drive is an enclosed engine component. The bike was designed by aircraft engineers to be reliable, and they succeeded.
A vast wealth of reliability information flowed from the battlefields of World War II. Engine design changed drastically as a never before seen sample of machinery failed and was immediately researched, improved, and fielded. Nothing like fighting for one's way of life to spur innovation. Aircraft engines went two directions at this time. Slow turning, super-reliable radials like the R-2800 Double Wasp added power by stacking on more cylinders.

Higher revving, less-reliable but higher performing inline V's like the Merlin went for higher and higher compression, more valves, hemi compbustion chambers, and superchargers.

Sounds like your bike came from the radial school of thought. My only real gripe with radials is that they leak oil and there's nothing you can do about it except carry a pan around with you.

MotorcycleWriter screwed with this post 02-06-2014 at 06:19 AM
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