Never hear of this one, driving Moto Guzzi.... and how about milions of Beamer boxers!!!

Hmmm....not sure about that "gyroscopic"thing....I've owned and driven wartime zundapp outfits, beemers an d I've owned a Chang Jiang, (r71 copy) a m72 ural and the two wheel drive Dnepr...only sold it a few months ago and I have to say the eastern block stuff handles worse than the BMW stuff, they are pigs really, but I have never heard or felt that effect....i've rebuilt a Dnepr box and I don't believe the revs or torque or flywheel size would be enough to cause that problem........even at full revs in neutral there's not any effect...I have started a 750 lump sat on the floor and it didn't hop about....so, I doubt it.

They just don't corner at speed...simples

Good workout though...

Hi Ipgo and Macabry

I can't say why that bike in particular was so bad ... perhaps the weight of the flywheel is relevant. I used to have a Honda CX500. On this bike the effect was engineered out, by adding a large counter rotating clutch. On my current bike, a BMW K100, there is no such counter balance .... except perhaps the drive shaft, and the effect is minimal on this bike.

I'm not saying a 2CV engine based bike would suffer, just be cautious and avoid that brown trouser moment

Another interesting feature of these bikes (and the Guzzis) is that the crank is positioned longitudinally and there is a torque reaction when you blip the throttle and increase rpms suddenly. The bikes leans to the right if you do that! It's funny but you get used to it quickly.
The advantage is that the gyroscopic effect generated by the crank, is at 90 deg to the axis of the bike and thus you don't fight against it when you lean in a curve. The only gyroscopic effect keeping the bike to its course is from the wheels, and this is the reason why the BMW Rs are so flickable compared to the size and weight. You must ride such a bike to feel this for yourself. These bikes are really easy to ride and can sometimes surprise other riders in the right twisties with the right rider!

From my own experience of running a Sunbeam S7, it's only under hard acceleration or deceleration that the torque reaction of the spinning engine and flywheel become a problem.
Changing up into 2nd at high rpm in 1st would result in the machine trying to squirm sideways underneath you, which wasn't much fun given the lack of grip from the tyres back then...

"wasn't much fun given the lack of grip from the tyres back then... "

Avon 500/16 roadmasters look bloody lovely though...

speaking of Sunbeam S7s...

Now that really IS a neat engine transplant!

Those bikes are beautiful, i've got an s7 tank on a bobber project of mine...really are beautiful bikes.
Interesting design history too, the design was originally supposed to use a boxer style engine as the the s7 design concept was partly taken from zundapp as war reparations...apparently sunbeam thought the boxer engine looked too "German" so the went with the infamous overheating and oil leaking twin instead...

Kinda looks good with the boxer though...

Having ridden BMW flat twins from 500cc Earles fork models right upto the 1100cc variations,as my own bike s and police models,I've never had any odd handling problems caused by the rotating mass of the flywheel.Ok you can feel it when stationery blipping the throttle,where you get a slight roll left to right,but not much else.

I have to differ with you Roger over the K100 layout as the crank drives the clutch and flywheel via a split gear, the mass of the rotating masses are cancelled out,by the counter rotation of the two. At least thats the theory. Oddly enough the RS and RT model had isolastic engine mountings in an attempt to make them smoother. Having owned both the basic K and an RT I don't think it was over succesfull.I found the RT had a high frequency vibration that you could feel through the saddle,this on both my own and job bikes.

DSCF4802 by 2steamhorses(Bob), on Flickr

This is a French built outfit with a GS engine.