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Old 10-18-2010, 06:34 PM   #1
StephenB OP
G(/)S ... what else!
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Joined: Aug 2005
Location: Ontario
Oddometer: 2,044
Planned mix 'n max Airhead engine build (1969-1979)

What problems of mechanical/fitment nature will I be facing when I assemble these parts to an engine:
  • /5 stock engine case (03/72 SWB R60/5)
  • /5 stock crankshaft
  • 336 "sport" cam for airheads from 1979 on (key'ed for bean can and square drive (flats) to inner oil pump rotor side)
  • single row timing chain
  • 1979-1980 timing cover with hydraulic chain tensioner
  • points in beancan
  • 107mm alternator
  • /5 engine cover (or any other for that matter)
  • 750 (or 900cc) barrels, pistons and heads
The 336 "sport" cam (asymmetric 38-46-58-26) was originally designed to work with the 750cc engine in racing applications. It was retroactively approved for all engines with 40mm exhaust valves (R90/6, R90S, R100/7). Has anybody first hand experience with using it in a 750 or 900cc engine? What if I added the thinner base gasket to raise compression by about 1/2 a point?

I want the bike to be an everyday rider with the extra power available when it is needed or desired. The mods should not affect gas mileage or reliability ... if possible. Am I asking too much?


Some of the above is fact, some is fiction, some is my personal imagination and some is just simple truth. [me]

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Stephen Bottcher
Ontario, Canada

'72 R75/5 The Blues
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Old 10-18-2010, 08:04 PM   #2
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Location: Washington, DC, USA
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no idea!
'85 BMW r80G/S--Another G/S on the road--Central America on a Shoestring--Nova Scotia on a Shoestring--Never Leave a Man's Behind

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Old 10-18-2010, 09:52 PM   #3
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Joined: Oct 2004
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Originally Posted by bgoodsoil
no idea!
me neither, but
Unintentional psychokinesis.
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Old 10-18-2010, 11:58 PM   #4
pommie john
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Joined: Apr 2008
Location: Brisvegas, Australia
Oddometer: 1,478
I run a 336 cam in my racer engine. Not having had any experience with any other cams in there, I can't say how different it is. It does produce good power with the max torque at around 4500-5000RPM, max power at 7000ish.

I have heard that you have to check valve to valve clearance with certain big valves, but I'm not sure how big the valves have to be before they clash.

The rest of what you suggest seems good as far as I know.

I have a /5 case, post '81 clutch/flywheel, later cam and bean can ( with Boyer installed). Make sure you use late model cam followers, ( not the ones with spiral cut outs) and the later rockers are supposed to be better.
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.
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Old 10-19-2010, 01:57 AM   #5
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Location: South France
Oddometer: 1,190
that sound interesting
Timing case 79/80 means no gears for mecanical tach
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