Engine specs

Heavy Flywheel to 78 RS specs but with siemens electronic ignition. clamshell RS airbox. Nothing wrong with the standard charging system for normal use.

The 78 I had was the best airhead engine I've ever had/ridden. pulled into the red in top gear on a 33/11 bevel box.
 
Call me stupid, and most do, I'd like a newly designed, efficient airhead boxer 400cc for a lighter weight bike to do long distance trials.

No idea what bike it would fit, but I'm sure you could build one around it.
 
Smallish diesel about 50 bhp twin driving a genorator no gear box no flywheel just very efficient at its optional running rpm. Of course drive is from a electric motor with a power output of about 100 bhp. The shortfall in power is provided by a battery lithium ion I suggest. It could do 20 miles from the battery and as far as you like with the engine running. Need a bit of real power that's when the battery comes into play. You could even have a small motor in the front hub. JJH
 
I take it you mean what selection of existing available parts, not how would you design a new motor.
If that is the case it would depend on what use you would be putting the bike too, and if you value high torque in the rev range you will use 98 % of the time over high horsepower in the range you use 2% of the time.
Almost all the tuning information you will read on BMWs seems to be aimed at the 2%ers
For example I recently read that someone is getting 110 hp out of 32 mm bings, which might suggest to some that 25 mm carbs would do OK on the average 52 hp 1000cc bike , and 29 mm would be good for almost any road bike, but most will tell you that you need 40 mm carbs to make decent power.
My F650 makes 65 hp / liter at the rear wheel with somewhere around 65 degrees less cam duration than a 336, measured at the mandated checking clearances, but most will tell you that huge duration cams are essential.
Some guys who are building high power motors only use new late pattern blocks, and some of the guys racing in the mid 70's reported head/ piston contact with anything less than the factory mandated 80 thou clearance, so I would use the best late model cases you can find if you intend going the high rev/ high hp route.
But again, others report no problems, without being too specific as to what the are actually running.
My small valve, small port, small carb , small chamber, small exhaust ,high comp, low geared 1000 cc G/S actually flies along the road as fast as bikes which claim twice the HP that BMW claimed for the R80, so for me low speed torque is the king.
 
Beemerboff said:
My small valve, small port, small carb , small chamber, small exhaust ,high comp, low geared 1000 cc G/S actually flies along the road as fast as bikes which claim twice the HP that BMW claimed for the R80, so for me low speed torque is the king.
Click to expand...

Same here - low to mid torque range every time, unles of course you are racing the dam thing on a track when prolonged WOT is required.

My (same spec as Beemerboffs) G/S fair stomps along at speeds you spend 98% of your time riding at, constantly surprises me with its competence/speed, often leave the odd power ranger looking a bit stupid.......

So dont think I would change it.
 
JJH said:
Smallish diesel about 50 bhp twin driving a genorator no gear box no flywheel just very efficient at its optional running rpm. Of course drive is from a electric motor with a power output of about 100 bhp. The shortfall in power is provided by a battery lithium ion I suggest. It could do 20 miles from the battery and as far as you like with the engine running. Need a bit of real power that's when the battery comes into play. You could even have a small motor in the front hub. JJH
Click to expand...

I'd like this but with half of everything suggested, including the weight.
Preferred engine configuration would be a transverse V twin, just because I like the noise they make
 
Beemerboff said:
I take it you mean what selection of existing available parts, not how would you design a new motor.
If that is the case it would depend on what use you would be putting the bike too, and if you value high torque in the rev range you will use 98 % of the time over high horsepower in the range you use 2% of the time.
Almost all the tuning information you will read on BMWs seems to be aimed at the 2%ers
For example I recently read that someone is getting 110 hp out of 32 mm bings, which might suggest to some that 25 mm carbs would do OK on the average 52 hp 1000cc bike , and 29 mm would be good for almost any road bike, but most will tell you that you need 40 mm carbs to make decent power.
My F650 makes 65 hp / liter at the rear wheel with somewhere around 65 degrees less cam duration than a 336, measured at the mandated checking clearances, but most will tell you that huge duration cams are essential.
Some guys who are building high power motors only use new late pattern blocks, and some of the guys racing in the mid 70's reported head/ piston contact with anything less than the factory mandated 80 thou clearance, so I would use the best late model cases you can find if you intend going the high rev/ high hp route.
But again, others report no problems, without being too specific as to what the are actually running.
My small valve, small port, small carb , small chamber, small exhaust ,high comp, low geared 1000 cc G/S actually flies along the road as fast as bikes which claim twice the HP that BMW claimed for the R80, so for me low speed torque is the king.
Click to expand...
Yes the plan is to use existing,readily available parts,I have a 1983 g/s short motor which is currently undergoing full refurb,new mains,big ends,oil pump etc,
I also have a pair of 800 nicasil barrels that I plan to rebore and fit omega high comp pistons 1000cc.
A customer suggests he has a pair of 100 heads( spec unknown)
The rest is a clean sheet,I'll buy what comes up at the right money,
Most advise small port/ valve,32mm carbs but I have a hankering to up the game a bit:D
,interested to here different opinions,plus any good info links:thumb
 
An interesting exercise would be a side valve turbo with modern production methods to overcome the inherent inefficiency of this engine layout. I wonder if the inadequate combustion chamber could be overcome with turbo charging? It would be a very small and light engine compared to the overgrown beasts we see on bikes and cars. Look at a modern boxer engine. See where the head joins the barrel? It's possible to have a engine about 1 inch bigger than that. Yes you would loose some efficiency but would the lighter weight and size coupled with a turbo compensate? After all when you put a turbo on a engine you would normally lower the compression ratio. JJH
 
mikeyboy said:
:augie:augie
Another session of cleaning and I can fit the main bearings and crankshaft :drool
Click to expand...

Why did you paint it?

It's from the era when metal was metal and didnt dissolve and would have developed a patina rather than a scabby paint finish :hide
 
nick.ct said:
Why did you paint it?

It's from the era when metal was metal and didnt dissolve and would have developed a patina rather than a scabby paint finish :hide
Click to expand...
Firstly it's not paint,it's been media blasted,etch primed and powder coated.
The finish should last years.:thumb
Also one mans patina is another's dirty corroded piece of junk:barf:D:D
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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