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Discussion Starter · #1 ·
Good day twinners, I have a question about the crankshafts in Honda twins with roller bearing big ends and mains, and it's this: How are the crank pins separated? (I don't need to do this but I am curious.) Also the pressure used to reassemble the crank, are we talking a magnitude of a few tons pressure or tens of tons?
Any insights appreciated ta.
Nigel.
 

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Special jigs and plates and a big press. 30 ton. I hear less than 20 to build up and there could be trouble. Google xs650 crank rephase and the guy developed a cylinder jig for assembly that looks like a good way to do it.
 

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Discussion Starter · #3 ·
Thanks Lefty. It seems to be a bit of a job to change the main and big ends when the time comes. Do you know if it was done often back in the day?
Nigel.
 

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I think the only reason people do it at all is for the peace of mind of having new parts. A good used crank makes good sense economically, and maybe from a reliability standpoint too, depending on the faith in whoever rebuilds it, using a mix of old and new parts. There might come a day where this service is more common for our twins. I think it's a lot more common for two-strokes. What bike are you thinking about?
 

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Discussion Starter · #5 ·
CL450, CB360 ; CB200 they all share similar bearings. One day they'll wear out. Then we will need to know how to repair/reclaim these cranks. I'd like to know how to do this when that time comes. I'm not an Engineer, but I can see a time when this knowledge is not obtainable. Then We're ***ked.
 

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Two members, Jack and Patrick disassembled sets to put in new rods, and clean bearings into 175/200 race bikes . Easy enough to pop apart with a 10 ton jack.
Jack used a very simple jig to get them back together ( also marked the parts before they came apart) a couple of vee blocks dial gauges and a copper mallet
To get them true
 

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In the UK, there's plenty of folks who rebuild two stroke cranks. Those have to come apart, in order to replace the centre oil seals on multi cylinder engines. Must be the same technique for rebuilding a CB crank.

Hillclimber 911 recommended a small local bike shop to me, Read Speed in Stourport. In my case, it was to do some cylinder head work, but the chap there told me they could rebuild cranks. They did 911s rebore on his 175.

And then there's Allen Millyard, who apparently scratch builds engines in his shed, using hand tools, including crank building.

Oddly enough, the manager / owner of my local Yamaha dealer ( used to be a Honda shop ) collects old Hondas, and he told me that the 175s were well known for crankshaft problems, and that he'd had to have a couple of his rebuilt. Which doesn't sound right to me, 175/200 cranks appear to be bulletproof.
 

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Thanks Lefty. It seems to be a bit of a job to change the main and big ends when the time comes. Do you know if it was done often back in the day?
Nigel.
It was never done back in The Day - a new 450 crank was only $75 or so (maybe less, can't remember).
 

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And then there's Allen Millyard, who apparently scratch builds engines in his shed, using hand tools, including crank building.
If he's building the stuff I've seen in a shed, I'd love to see the shed... :lol:

Which doesn't sound right to me, 175/200 cranks appear to be bulletproof.
I couldn't agree more, not sure what he experienced or saw. My Dad built a 175 drag bike long ago and my cousin and I raced it mercilessly for a year or so and it never had any problems, much less crankshaft. The cam in it let it make power up to 11,500 rpm and we used to come off the starting line at around 9000
 

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I think he means garage, Tom.

Translation : UK shed = NA garage

BTW, I did split my crank on my old BSA single (on a gas station parking lot).
There is a threaded 'plug' on the inside of the crankpin on those and that came loose.
The rod came around and everything stopped...lol.
Lined the wheels up by eye, locked the crankpin nut, and re-assembled.
Drove it off their lot the next day...lol.

It was such a reliable machine, I kept every tool I needed for a complete tear down in the tool box !
(I constantly over-revved it and could change a valve almost blindfolded on the side of the road)....did it many times....lol
 
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Discussion Starter · #11 ·
It just shows: a new crank today is not only unobtainable but nearly 20 times the price! It's crazy!
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Regular oil changes for my engines from now on gotta protect my assets! It also gives you an idea of what to pay when/if you do need new mains or big ends. I've got a CB200 crank where the big ends have gone on one side and I have about 1/2 inch of play up and down. I think a second hand crank from fleabay might be the cheapest option!
Nigel.
 

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Discussion Starter · #12 ·
Ha ha Uk Shed is a small, usually wooden construction building in the garden where mechanically minded gentlemen spend their evenings tinkering with engines. can be small 6'x4' up to 10x16' or bigger, the garage is where the car or the completed and running bikes are kept if you are married, otherwise you can keep them in the living room where it's warm and dry. I call mine Shed-quarters. That's where all the goodies are.
 

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My "shed" is 26x36, full attic with pull-down stairs, insulated, has 2 wall unit 220v air conditioners (newer one heats as well) and a half bath... got lucky and bought it that way. :D and I can't build 1% the stuff Millyard does (but at least I'm comfortable)

I'd just be buying a used crankshaft, myself...
 

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Discussion Starter · #14 ·
That's even bigger than my Living Room! Good job I've got a spare bedroom!
 
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