SOHC.co.uk Forums > The Black Bomber Board
Bomber crank refurb
K2-K6:
"It makes it almost impossible to build a 6"
I believe his replica of the Honda racing 6 is plain bearing construction, made from combining more than one engine, but I've not seen what he did to construct the crank.
Usually, the route would be to get a bespoke unit made and likely a forging or machined from billet. Possibly also derived from welding two crankshaft together if they are welding compatible steel.
Irony there is that the original Honda 250-6 is a push together crank. Apparently they went so far towards small construction that each successive crank pin going in from the outside steps up in size as it has to transmit more torque to the centre location drive train, with the rods bearings etc following in size. Pretty exotic in design, even now.
AshimotoK0:
This is how he designed and built his RC374 6-Cyl replica crank. Genius!
https://www.youtube.com/watch?v=J1cQ098eqF8&t=450s
K2-K6:
Ooh, that is clever. I thought the original crank cases (and by default, the bearings) are plain, but hadn't seen how he did that effectively converting to roller bearings.
Very clever chap, but needs to grind his lathe tools better to improve first run finished surfaces ;D
Johnwebley:
--- Quote from: AshimotoK0 on March 03, 2021, 05:01:31 PM ---This is how he designed and built his RC374 6-Cyl replica crank. Genius!
https://www.youtube.com/watch?v=J1cQ098eqF8&t=450s
--- End quote ---
Nearly all available on YouTube.
He does use Yamaha engines.
I love his relaxed style.
And his addiction to cup cakes.
Sent from my SM-A750FN using Tapatalk
K2-K6:
Notice he pinned the journals too, to prevent them rotating under torque load.
The original Honda apparently can't be loaded at to low an rpm to reduce the risk of twisting them out of phase, with the rev counter staring at something like 8000rpm ! And useable range above 14000rpm.
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