wouldn't this be great in a proper frame?

[736cafe]

http://thekneeslider.com/archives/20...r-monkey-bike/

[Geeto67]

provided that proper frame is on a mount in the living room - I can't think of a more useless engine - 125cc four? really? why? it is cool that the guy did it just to say he did it but no torque marginal hp and you have to rev the crap out of it to go anywhere. A 125 single would smoke that puppy 6 ways to sunday.

[buckandaquarter]

That's the same guy that did the 4 valve BMW heads and the V8 Ducati.

Also, remember back in 65 Honda built a 125cc 5cylinder and a 250cc 6 cylinder bike for GP, not to mention various 50cc twins, etc.

[Geeto67]

back in the day the prevailing thinking in road racing was the smoother the engine the better the traction because you didn't have jerky quick pulses knocking the bias ply tires loose (whether this is actually the case or not is beyond my pay grade), that is why honda built 250cc 4 and 6 cylinder bikes. If you ask the guys who rode them they were fast when moving but you were not going to take any parallel twin off the line.

As tire technology improved it became aparent that staggered pulses helped traction so racing shifted back to v motors from inline fours and firing orders changed to make motoGP 4 cylinders act like a really big twin because a large pulse with time to slow down between the next pulse gave better traction than a bunch of shorter close together pulses that were overpowering the tire constantly.

a vintage 125 single would rock that 125 four cylinder out of the hole based on just the largeness of the stroke, and a modern 125 would def stop a mudhole in its ass and walk it dry. The 125 may rev to a million and make more overall hp but that is pretty much useless in street riding or any kind of stop and go. I imagine that the 125 4 would work best as a road race bike on a track with more sweepers and less tight corners. but remember as a 4 cylinder you would probably be carrying a lot more weight than a comparable 125 single.

[KeninIowa]

Monkeys are soo light. They have no throttle control. They're unfamiliar with traffic laws; no stop and go, just go. A 125 multi is the ultimate Monkey Bike GP weapon, duh.

That is fucking awesome. I hope someday to have the time and tooling to say "I'm gonna build me an engine outta this aluminum stock."

[Hoofhearted]

Honda made (in the mid 60s)a 5 cylinder 125 GP machine and at the same time Yamaha had a Vee four 125. Both hidiously fast in the day. And had plenty of acceleration. I'd pit either of them against any modern 125 single. They weren't designed for stop and go but were great for racing.

[borzwazie]

that is 6 kinds of awesome.

I think the thing I like about it the most is that if you didn't actually see it, but heard it coming, you'd think it was some kind of racebike - and then this little clown bike roars past.

It's like the ferocious Chihuahua of motorcycles - all yap!

[buckandaquarter]

Probably not much torque, no. The 125-5 supposedly made 35HP at an insane 20krpm and needed 8 speeds to harness those tiny screaming ponies. What does a modern 125 single in race trim put out? I'd take the modern single for a drag race, but a screamer like that has got to be fun. Dry weight is reportedly 85kg, so about the same weight power output (claimed 30 paper ponies on the CR) of my CR125 2 stroke single dirtbike.

[Fang]

I was really hoping for a more compelling video. IT seems to run well, and sounds dinky.... But I was wanting to see some wheelies, some bits of FAST acceleration, powerslides through the turns or something fancy like that.

Still, one-off motors are really cool.
-fang

[oneworden]

That same guy is building a V8 Duc using almost stock cases.