Early GS works bikes/Herbert Schek

GS

Quick question - does anyone know whether there were any massive differences between a 80g/s frame and the road version. ie engine position. Presume that different brackets for different bits and pieces and swingarm longer.
 
Rupsol said:
the only change i would make would be to have an up and over exhaust. Beautiful bike.
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It is, isn't it :thumb2

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GS

had a look in the garage last night and have the following bits for a build

maico 42mm yokes
17.5" Ohlins piggy back shocks and also 15 3/4 piggybacks both from Husky enduro bikes
Husky twinleading from wheel and backing plate
70's Husky alloy tank that is virtually same as the maico
Husky seat unit.
Need some 81 Maico 490 forks, and a donor bike. Have my eye on this one on ebay

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120728757612&ssPageName=STRK:MEWAX:IT

I hope it remains cheap. I would guess £600 to £700
 
Rupsol said:
Quick question - does anyone know whether there were any massive differences between a 80g/s frame and the road version. ie engine position. Presume that different brackets for different bits and pieces and swingarm longer.
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Interestingly Dogbytes and I have been comparing a g/s frame (well actually st) and a later 92 GS (paralever frame ) . The frame is ostensibly the same.. except the top frame tube is twice as thick. We obviously haven't sectioned the other frame tubes but it does make you wonder if these aren't thicker as well.
 
pete.keys said:
come off it Matt ... you have hung out on this forum for so long you could probably strip and rebuild an airhead with your eyes closed :beerjug:
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Regrettably not - they remain a strange but tantalising temptation :D

However airhead ownership is almost inevitable at some point ...
 
GS

pete.keys said:
Warning Warning Will Robinson: i think the crank throw on the 650 is smaller than the 800/1000 so its not a simple piston/barrel upgrade
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Doesnt matter - if the chassis turns out well then I will have a special engine built for it. Or rebuild the 650 with mikunis/gas flow etc. Dont forget for Enduro I dont need anymore than 45 odd hp. More power will be a hinderance especially with my lack of throttle control.
 
GS

pete.keys said:
Interestingly Dogbytes and I have been comparing a g/s frame (well actually st) and a later 92 GS (paralever frame ) . The frame is ostensibly the same.. except the top frame tube is twice as thick. We obviously haven't sectioned the other frame tubes but it does make you wonder if these aren't thicker as well.
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From my research they are all fairly similar. Like Husqvarnas...all the engines from the early 70's all interchange up until 84/85 when they went monoshock. Even the fourstrokes fit in the 2 stroke chassis.
 
pete.keys said:
Warning Warning Will Robinson: i think the crank throw on the 650 is smaller than the 800/1000 so its not a simple piston/barrel upgrade
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That appeals to my sense of humour... the 'Lost in Space' robot turns out to be an expert on BMW airheads.

The wiki.classic-motorbikes.net article is illuminating. "The 800cc engine utilises many parts from the R65 model including the crank, rods and barrels which have been bored to 90.8mm and externally shorn of every other fin. This not only saves a considerable amount of weight but also prevents them from clogging with mud."

"A similar format of R45/65 engines was also used by Laszlo Peres on the factory bikes but here the similarity ended."

So, the engine had a bore and stroke of 90.8mm x 61.5mm to give a displacement of 800cc, compared to the 82 x 61.5 mm of a standard R65. That's massively oversquare, I'd be interested to try one out.
 
Richard A said:
That appeals to my sense of humour... the 'Lost in Space' robot turns out to be an expert on BMW airheads.

The wiki.classic-motorbikes.net article is illuminating. "The 800cc engine utilises many parts from the R65 model including the crank, rods and barrels which have been bored to 90.8mm and externally shorn of every other fin. This not only saves a considerable amount of weight but also prevents them from clogging with mud."

"A similar format of R45/65 engines was also used by Laszlo Peres on the factory bikes but here the similarity ended."

So, the engine had a bore and stroke of 90.8mm x 61.5mm to give a displacement of 800cc, compared to the 82 x 61.5 mm of a standard R65. That's massively oversquare, I'd be interested to try one out.
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Ask StEptoe about the short barrel specials :augie
I turned one down many moons ago, and have been kicking myself ever since :comfort
 
short stroke engine

When up with Richie Moore a few weeks back he said that he was currently building a racing 750 short stroke engine... although for what purpose and what the benefits of it would be over a longer stroke I don't know.
 
pete.keys said:
When up with Richie Moore a few weeks back he said that he was currently building a racing 750 short stroke engine... although for what purpose and what the benefits of it would be over a longer stroke I don't know.
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Id guess it's because short stroke motors are usually higher revving although have less torque which is probably not so much of a factor in racing. Due to the wider bore, you can also fit bigger valves in which can increase power. Although getting all this to work means getting cam profiles and timing, carburation, materials and a host of other considerations right (which is where experts like Richie Moore come in :D )
 
According to those that have tried, the main factors they found which limited revs on airheads are the the pushrod/tappet angle, and the flexible crankcase.

I suppose the lifter bores could be welded up and rebored at the correct angle to give the lifters a straight push at the pushrods, and if the short stroke was combined with long rods which had a straighter push at the crank that would help with the lack of crankcase rigidity , but at the business end the need to keep over 70 thou piston to head clearance negates much of the the benefit of a few extra revs.
 
GS

As I have said this bike will be built with vintage enduro in mind and maybe (if I am brave enough) the odd vintage scramble and LDT. So want torque and low end pull and midrange. Revvy motors are no good in the miub...and neither am I:thumb2
 
GS

having considered this project for some time now - my one concern is stripping the starter motor off and having to use the bizarre kickstarter. many articles I have read all say that BM's are difficult to start. I am used to starting big singles so should I be worried. Or leave the starter on and have a lightweight gel battery. Any thoughts? A bike that wont start may as well be used as a boat anchor. Do they bump easily with the shaft drive?
 
Rupsol said:
having considered this project for some time now - my one concern is stripping the starter motor off and having to use the bizarre kickstarter. many articles I have read all say that BM's are difficult to start. I am used to starting big singles so should I be worried. Or leave the starter on and have a lightweight gel battery. Any thoughts? A bike that wont start may as well be used as a boat anchor. Do they bump easily with the shaft drive?
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Starter and lightweight battery is way to go..
I can kickstart my 90s and my 80g/s but it is a hit and miss afair...
Only ones I could kickstart almost every time was my R26 [no leccy foot] and my 60/6..:thumb2

Bumping imho is a big no no :nono:nono so much stress and a tendancy for the bike to want to follow torque effect of the driveshaft, leads to bike falling over on someone :augie :(
 
I watched Syco trying to kick Camille into life at one of his Shropshire do's - he nearly passed out. An electric foot sounds a good idea to me :D
 
I agree with them two up there.

You could try it without the starter,

:robbut I'm guessing that by the time you've picked yourself and the bike off the ground and got going again for the second time in five minutes. You'll be straight back to the garage and refitting the leccy kit.


In years long gone I did a bit of street class drag racing. To qualify all the lights had to work. But to keep the weight to a minimum we binned the generator and ran all the electrics 'including electronic ignition' from a 4" square gel battery, connecting it to the van battery between runs.

All you'd need is a battery strong enough to turn the motor over for about 90 seconds continuously before going flat.

I remember a guy racing a 350 Morini turbo with water injection in the 1985 (iIrc) Weston Super Mare Beach Race. With no electric start he spent a lot of time kick starting the bike, which looked like it was giving him a really hard time.


Val.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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