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Author Topic: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)  (Read 315027 times)

Offline focusinprogress

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Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #930 on: Dec 13, 2017, 09:46:53 »
Been having a bit of a rough time but still plugging along. Making a piston holder to machine CB750 (SOHC) for CB500/550 591-605 conversion. As usual, overbuilt but I know from previous piston machining it eventually saves a ton of time plus no chance of distorting pistons. Can also use 'pull piece' to check all piston tops are lsame height. Couple of pics, still needs drilling, tapping and a few bolts plus a 'piston pin' to hold everything together. There will be a drawbar through lathe spindle to allow piston tops to be machined.

I've revised my cb650/550 hybrid engine build because I couldnt find anyone capable of machining forged 836 kit wiseco pistons.......and now you post this......
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Offline crazypj

  • Posts: 12950
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Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #931 on: Dec 13, 2017, 22:08:41 »
It's difficult to find anyone who does motorcycle part machining and modification. Majority of 'engine shop's' can't or won't do anything smaller than 80mm.and multi cylinder. Even less places have any type of piston holders. In my experience, a machine shop may be able to do what you want but you have to be incredibly specific, including clearances and surface finish. They then charge accordingly (usually way over the top as they would rather do stuff they do regularly)
'We' used to give 'awkward' customers with weird old bikes realistic estimates, plus 100% if we thought it would take too long or be 'difficult' to get parts (in a dealership it's much easier to do whatever manufacturer you have)
Anyway, if you decide to do something different, let me know in the new year
Oh, I also radiused the lower edges of the 'pull piece so it will fit into pocket. Because of the less tan stable mount in vice I could only mill one direction and had to rotate part so I was cutting towards vice which is why the round-over is going in opposite directions. I doesn't matter though as function is the important part. The offset is deliberate as gudgeon pin is not on centreline of piston. Piston skirt fits onto lower edge to centralise.
 The bars have to be drilled and tapped, I'm going to re-machine the internal 'dome' to match machined piston crown.
A long 'pin' through gudgeon pin hole will have long Allen bolts either end to clamp into 'cap'
« Last Edit: Dec 13, 2017, 22:41:34 by crazypj »
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline crazypj

  • Posts: 12950
  • Split personality, I fake being smart
Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #932 on: Dec 17, 2017, 16:46:02 »
99% finished piston holder, time to start carving on stuff. I didn't think 15 degree's was correct so got out scrap head to do some measuring.
I'm getting closer to 26 degrees included angle which gives 13 degree chamber angle when I used both hands, in pic, it looks more like 30degrees. I  couldn't hold camera and angle finder properly
 Anyway, piston mounted and running true(I checked with DTI)
Anglefinder 'in' combustion chamber
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0



Offline crazypj

  • Posts: 12950
  • Split personality, I fake being smart
Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #935 on: Dec 17, 2017, 23:16:53 »
I'm lousy at computer graphics, easier and quicker to just do a rough drawing, then scan and post (couldn't be bothered to get to scanner so took pic.
Top part to represent piston modification, 3mm  dimension is missing from top left, the 12 degree angle continues a little high but  with only 3mm flat compression may well be higher than with specified 6mm flat and 15 degree angle? I've got a prototype machined, one of the 0.75mm OS pistons I'm going to use in my 550 (eventually?)
Oh, 55mm is the measurement across the chamfer of combustion chamber and not original 550 bore
« Last Edit: Dec 17, 2017, 23:22:48 by crazypj »
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline crazypj

  • Posts: 12950
  • Split personality, I fake being smart
Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #936 on: Dec 18, 2017, 11:53:22 »
I think I may have a reason for the steeper angle. The original mod was done on a 500f. I can't remember if combustion chamber is same as 550 or is similar to CB750 having no angled 'squish' area?
Here's pic of top, probably going to reduce diameter (or increase flat) to 54mm to make sure there is clearance with combustion chamber. Valve pockets will need machining to at least 550 spec
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline crazypj

  • Posts: 12950
  • Split personality, I fake being smart
Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #937 on: Mar 16, 2018, 11:52:31 »
My little sister only told me yesterday, she bought a bike in November. Honda Varadero, but not the 996cc version, a baby V twin 125cc to comply with licencing laws in Britain. Never thought she would get on a bike as she was always a 'horsey' person
 Her horse is now officially retired though (22 yr old Welsh Cob, whatever that means?  ;D )
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline Sonreir

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Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #938 on: Mar 16, 2018, 12:12:51 »
If she's in northern Wales, isn't a cob a bread roll?
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Offline crazypj

  • Posts: 12950
  • Split personality, I fake being smart
Re: CB360's-from build to blog - 2013, MDS (Mo Dumb Shit)
« Reply #939 on: Mar 16, 2018, 12:48:29 »
LOL, yep. She moved down west Wales several years ago, more farmland for horsey.
Just been reading some Stephen Hawking quotes, liked these in particular

"We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special."

"We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet."

He disagreed with Voyager/Carl Sagan 'star map' don't let 'them' know where we are and obviously believed far superior intelligent life is 'out there'
« Last Edit: Mar 16, 2018, 12:52:42 by crazypj »
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0