Honda-SOHC
SOHC.co.uk Forums => The Black Bomber Board => Topic started by: AshimotoK0 on March 03, 2021, 02:08:13 PM
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My good buddy Graham Curtis just sent me this pic of my rebuilt '67 Bomber crank ... sludge traps totally full of crud but otherwise just needed stripping and cleaning. Evidently the copper coating is part of Honda's original hardening process.
We did a deal where I gave him my three spare cranks I got from Crawley (well 4 actually as I gave him one to 'experiment' on last year ;D) .... to make me one good one and used the rest for other peoples refurbs.
If you have a pressed-up Honda crank ..Graham is your man.
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ASH,are the sohc 4 s cranks pressed up?
I know the Z1 is,from watching Allen Millyard.
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Nope cast and ground with shells
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Nope cast and ground with shells
That's what I thought.
It makes it almost impossible to build a 6
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my understanding
CB400F ... CB500/550 /4's , CB750 SOHC's have plain bearing one-piece cranks
Z1 /Z900 cranks pressed -up roller bearing
Z650 Plain bearing one-piece crank
GS550 .. GS750 .. GS1000 crank pressed-up roller bearing .. so you could make a Suzuki GS825 6 /cyl from 1.5 GS550 cranks :)
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"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.
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This is how he designed and built his RC374 6-Cyl replica crank. Genius!
https://www.youtube.com/watch?v=J1cQ098eqF8&t=450s
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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
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This is how he designed and built his RC374 6-Cyl replica crank. Genius!
https://www.youtube.com/watch?v=J1cQ098eqF8&t=450s
Nearly all available on YouTube.
He does use Yamaha engines.
I love his relaxed style.
And his addiction to cup cakes.
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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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There was a time when Z 1000 cranks were welded if going racing, actual seen a Z1000 with 3 pistons level and 1 at top
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There was a time when Z 1000 cranks were welded if going racing, actual seen a Z1000 with 3 pistons level and 1 at top
The timing must have been a little out on that Bryan!
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It actualy drove in with a "missfire" mate
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He's done a beautiful job on that crank Ash, a real credit to him.
We forgot that in our ramblings :) it does look particularly good work Ash.
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Those videos kept me amused (and amazed) for quite some time, what fantastic work and he does sound so casual about it all.
Cheers
Dennis
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Think he has some help with setting up the crankshaft alignment by employing miniature engineers.
https://youtu.be/uTSLUaTjvqw
;D
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Apologies for thread drift Ash
https://youtu.be/81UjjSH2iFw
What an amazing process.
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I think the 1st production CB750 cranks in 1969 were ground using a Swiss made machine.
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Yes amazing machine Nigel. I designed the closed loop water flushing valve system for this company.. which all started in the UK Coalville) . Amazing CNC machines which can spark erode (EDM) tiny holes to amazing depths and tolerances.
https://www.winbrogroup.com/wam/edmdrilling/
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Top job on the crank Ash, but I thought you were going to use the pressure flushing method devised by Jenson? I had mine taken apart and cleaned, you just cant better getting in there and having a look.
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Top job on the crank Ash, but I thought you were going to use the pressure flushing method devised by Jenson? I had mine taken apart and cleaned, you just cant better getting in there and having a look.
I gave Graham a crank I had to 'experiment' with last year ... he re-furbed it and put it for sale on FB (with my blessing :) ) and Jensen bought it ... so that kind of made my mind up to let Graham do mine to. Graham reckons that the sludge is so highly compacted on old Honda cranks that you would never fully remove it without stripping the crank. The design is such that the crud is more inclined to be deposited in the crank web holes rather than the centrifugal oil filter, located on the end of the crank.
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The guys that did mine said the exact same thing. I told them about the power flushing thing and they just laughed, That said, when they stripped mine they said there was hardly any crud in there, one of the cleanest he had seen in a while. So probably a waste of money having it done but there was no other way of knowing that information.
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The "crud" I believe comes from effectively taking the oil over temperature locally to bake it in a sticky mollasses type looking residue.
It's something that newer oils are able to avoid and with significant benefit to running things like this. I don't prescribe to the "old engine, old oil" theory if it can't be proven with good logic why that should be the case. The so called "synthetic" oils available have very significant advances in this area, susceptibility to heat damage, that just don't compromise in this way.
From various engines and where this effect is clear, it's usually accumulated at over heat sites rather than pure restrictions. In other words, temperature within crank components rather than just accumulation of junk getting stuck there.