From what I can tell it is info on the BMR-Suzuki Supermono race bike that used a heavily modified Suzuki DR800 motor with Apfelbeck head and twin crank, hence the interest in the machine from the French Suzuki DR group you linked the images from.
Our European season ended with a very nice 21yr old German lady named Katja Poensgen winning the championship riding a BMR-Suzuki. She achieved this by winning 4 out of seven races with one second place & 2 DNFs.
The BMR-Suzuki she rode is a very interesting tool. It may have started life as a DR800 motor but that was long ago & far away! It's creator is Rupert Bainzel, and apart from a lot of bottom-end work, the motor features a machined-from-the-solid top end, with an Apfelbeck type of cylinder head where the valves are arranged radially, with exhaust & inlet ports placed diagonally. As you can imagine, this calls for some hairy machining of cams, they are conically ground. It's watercooled and fuel-injected & gives over 90BHP from 741cc at 8000 & peaks at something like 9300rpm. Since this represents a BMEP figure of something in the order of 215psi it is a considerable achievement.
Of course, this didn't happen overnight, it's taken some years to develop it to the present pitch and I know that Rupert won't even think about how much it's cost!
Based on DR Big Single Cylinder Four-Stroke
Twin, Conical, External Belt Driven
Downdraught Electronic Fuel-Injection
94bhp @ 8100rpm
Aero-Space Quality Tube And Plate Steel Frame
Italian Supermono Championship, wins Constructor Championship and Title, racer M. Lucchiari
I wonder though if a deeper or more robust piston skirt would have solved that. Yes it would have increased reciprocating mass, but maybe not as much rotating mass as twin cranks? Plus that piston looks heavy with two wristpins and the rod mass has to account for something!
hoof: honda xr250 and bigger post 84. once even the 200 was RFVC.
twin cranks are ok provided balances and weight are dead accurate to each other. much discrepancy and those big gear couplings will get backlash thatwill have one eat the other then it's cocked piston time. makes more sense than a balanceshaft if done properly.
I picked up a used KLR650 to add to my fleet and replace my old 93 DR650. I got a really good deal from the original owner up in San Francisco. I purchased this for a couple of reasons... First... Me and my son want to do some adventure riding. He's going to pick up a KLR himself and sort it...
just a quick hello my name is Steve and im a bikeaholic.
been messing around with bikes for years but im NOT a mechanic, more of a muchanic, meaning that i muck about till something works.
Look forward to joining in