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BMW Airhead GS
Frankenbeemer - Project Plan
The intent here is to build a BMW Airhead fire road
Points of Concern
Charging System Reliability & Capacity
Air Filter Seal
Either a Monolever or twin shock
with modified rear suspension. Suspension travel in the eight inch range
should be adequate.
Frame Main frame is probably adequate for
bee-bopping along. Probably need to investigate reinforcing the subframe
if doing saddlebags
Footpegs & Foot Controls Need complete
Front Suspension - The forx from either stock twin
shock or Monolever should be adequate as a starting point, but with spring
and dampening mods. Twin shock forks should get a pinch bolt upper clamp.
Rear Suspension - Mono chassis probably only needs a
good quality aftermarket shock, perhaps a bit longer than stock to reach
the 8 travel mark. Twin shock swingarm and driveshaft probably needs a
2 extension to get acceptable travel with lay down shocks. Need to do
scale drawing. Need to research u-joint angularity limits.
Front brake a single 300mm floating rotor and 4
piston caliper. The under tank master cylinder is an excellent location,
immune from crash damage that would damage a bar mounted item. Can
optimizing the other components compensate for the cable actuation of the
master ? Can a G/S be retrofitted with an undertank ? Braided stainless
line from master cylinder to caliper.
Rear brake Stock drum format is probably
adequate, perhaps optimize shoe material and reroute actuating arm to
Rear rim 2.50 x 18 would be first choice, 2.15 x
18 would be OK
Front rim 1.85 x 19 would be first choice, 1.85 x
21 would be OK
Low front fender in plastic, rear some enduro bit
Fuel tank - /7 6.3 gallon (23.8L ) and/or 43L (11.4
gal ) with quick disconnect lines
Solo ? - probably depends on discovering a superior use for passenger
space. Dual /7 saddle really works quite well for lashing storage. Need
better seat attachment/release method.
Side covers -
of what value ?
Hand Controls Crash tolerant dirt bike stuff
would be highly desirable. Leave the choke by the carbs where it belongs.
Simple starter button on right, off-on-off on the left. Turn signal,
headlight on/off high/low high flash.
Instrumentation Analog speedo or inductive
computer ? Digital tach, digital voltmeter, oil temp
Lighting 7 Bosch 100/55 H4 or something wiz
bang which is considerably more compact, lighter and certainly
horrendously expensive. Is the wiz bang stuff serviceable in the outback
or are the component bits so small as to be inconsequential in storage.
All other lighting should be L.E.D., mini turn signals, tail and brake.
Perhaps separate but identical tail and brake modules with one spare.
Electrical Misc. Custom wiring harness, Mil grade connectors
An R80 seems best choice at first thought. There seems to be anecdotal evidence about superior longevity and the smaller engines 750 & 800cc generally have a better reputation for general overall civility. The iron barreled 980 is probably the least desirable. Intrinsic fuel efficiency of 800 vs 1,000 ? Is the 800 always more efficient at typical operating load conditions. Can you get have the added displacement without compromising fuel mileage. Some magic combo of displacement, heads, compression etc.
Stock cam seems best all round. Not aware of any intrinsic problems with stock lifters and pushrods.
Nikasil highly desirable, especially in any engine near or over 1,000cc.
Twin row cam chain.
Twin plug heads.
Electronic ignition with points system in situ backup. Can alternate advance curves compensate for crap fuel while still generally accommodating high compression for best fuel mileage.
Starter - ?? Bosch serviceable world wide ? Modified Toyota ?
Eurolast alternator & reg/rec., Need to calculate lighting & heating loads.
Air filter /7 setup is a
pain to service and looks pretty sketchy for seal. Could you take stock
covers, section them horizontally above garb inlets, weld lower halves
together and box them to make a still air chamber, cylindrical filter
attaches to top of chamber, old upper air box halves are filter covers
how to attach. G/S is probably a flat filter
Clutch Is stock hopeless or is maintenance the key to perfectly acceptable longevity. What is the truth about Touratechs ceramic friction plate
Trans mods to improve reliability. Is synthetic fluid a magic elixir. Aftermarket low 1st and high 5th ratios are certainly appealing how much. Kickstarter has rap for unreliability truth ? Would certainly be a handy emergency bit. transmission output shaft circlip seen this more than once, what is this about
Drive Shaft Can /7 and/or monolever shafts be rebuilt with serviceable u-joints ?
Final drive Ratio ?
Fabricate a custom electrical harness or rebuild a stocker? Certainly relocate fuse panel.
Frankenbeemer - Project Log