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Author Topic: 75 CB360 - bad omen "yatagarasu" build  (Read 39267 times)

Offline Popeye SXM

  • Posts: 192
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Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #140 on: Mar 25, 2018, 18:56:52 »
I like it. This way the stresses are spread over much more of the tubing

Offline Sav0r

  • Posts: 696
    • ChrisLivengood.net
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #141 on: Mar 25, 2018, 19:24:16 »
I used a very similar arrangement on my sub frame build. Though I put the hard point directly through the cross section of tube and gusseted the junction exactly like your model. I had the advantage of using a fairly large OD tube which made that possible though my build is in aluminum. Several thousand miles and 4 years later and it hasn't failed yet...
Sav0r the adventure.

Visit www.chrislivengood.net to get more information on my RD350 dubbed Mia Wallace as well as my other projects and snafus.

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Offline teazer

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Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #142 on: Mar 25, 2018, 19:32:13 »
That looks right now.  Brace/gusset metal can be remarkably thin and stl  be stiff & strong enough.

Offline MiniatureNinja

  • Posts: 521
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #143 on: Mar 25, 2018, 20:15:42 »
oh yea

and I got the pistons in and measured the deck with the cylinders installed - no gaskets. there is a .053" gap. I have a copper gasket from Lanni for the head, which is .042" which means I need .011" to get to "zero" deck - but Lanni only makes them as thin as .016

an "N.E." brand base gasket measures .020 but I can "squeeze it" with the caliper to get it to .0195
'75 Honda CB360 - thread

Offline crazypj

  • Posts: 13454
  • Split personality, I fake being smart
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #144 on: Mar 25, 2018, 22:55:06 »
Just realised your thread name is prophetic, you sure you don't want to call it 'lucky f****r' or something instead?  ;D
You have one of the 'top' tolerance motors. ( or bottom tolerance?)
When I did my first 378 I skimmed 0.020" from block and head and still had clearance. Couple of 378 builds have had zero clearance even with a stock base gasket and been negative with skimmed block. Honda obviously was lying when they said what tolerances were being used (although, pretty sure they never gave a main bearing to crankcase or block deck measurement?)
It's added expense to have block skimmed but much easier to remove material than to add it back. Oh, just read post again, you need about 0.035"~0.040" between piston top and head, the 0.053" is how far piston sticks out at present?
 As for shock mounts, you could probably run a 5mm drill all the way through using current threaded hole as guide then flip them over and drill 1/2"~3/4" to lighten them. Just be careful not to go too deep, about 1/2"~3/8" minimum to shoulder. Drill press will do it, I would use a pretty low speed and slow feed though (~300 rpm and 'feel' the cut)
Just had another thought to help with alignment. Counter bore for a short piece of conduit or similar, make mounts 'a solid bar' line everything up, weld in place, cut conduit and pull it out
« Last Edit: Mar 25, 2018, 23:12:09 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 MiniatureNinja

  • Posts: 521
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #145 on: Mar 25, 2018, 23:11:19 »
Just realised your thread name is prophetic, you sure you don't want to call it 'lucky f****r' or something instead?  ;D
You have one of the 'top' tolerance motors. ( or bottom tolerance?)
When I did my first 378 I skimmed 0.020" from block and head and still had clearance. Couple of 378 builds have had zero clearance even with a stock base gasket and been negative with skimmed block. Honda obviously was lying when they said what tolerances were being used (although, pretty sure they never gave a main bearing to crankcase or block deck measurement?)
It's added expense to have block skimmed but much easier to remove material than to add it back. Oh, just read post again, you need about 0.035"~0.040" between piston top and head, the 0.053" is how far piston sticks out at present?

yes, .053" is how far the piston sticks out with no gaskets at all. so if I add the .042" headgasket, then they would stick about .011 past that...
'75 Honda CB360 - thread

Offline crazypj

  • Posts: 13454
  • Split personality, I fake being smart
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #146 on: Mar 25, 2018, 23:20:22 »
 In that case you need ~0.047" base gasket to get 0.036" piston to head clearance, slightly thicker won't do any harm (there is at least one 378 where compression seems 'too high' when kickstarting)
You have 'low' motor
'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 MiniatureNinja

  • Posts: 521
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #147 on: Mar 25, 2018, 23:30:40 »
ok gotcha, so it looks like Lanni makes a .050 gasket thickness, should do it. by 'low' you mean the case is milled lower than average, so everything sits down further - causing the need for thicker gaskets?

the machine shop that did the boring of the cylinders did express some concern with the clearance numbers I gave him, saying that the higher compression may play some havoc with such tight clearances - I am 100% OK using higher octane gas as where I work I can get any flavor sunoco for cheap, and I do have the ol' electric leg for starting purposes

oh, and "Yatagarasu" is a mark of rebirth and rejuvenation (sorta what I am doing do this bike) and also a god of guidance, which I gladly accept from the many experienced members here!
« Last Edit: Mar 26, 2018, 00:33:16 by MiniatureNinja »
'75 Honda CB360 - thread

Offline 540Nova

  • Posts: 102
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #148 on: Mar 26, 2018, 00:52:01 »
In that case, welds are pretty good as it takes practice to make them pretty as well as strong.
Probably turn up amps slightly and turn down wire feed so you can burn in 'pretty welds' (you can work slower, I still remember the first time I used MIG, set up for 3/16" plate, I tried using on 1/16" sheet  ;D )
I thought you were paying buggy makers to weld it. :-[
Ca. is a bit OTT with some hobby stuff, seems they only want 'professionals' with crazy amounts of extractors, scrubbers, etc to do 'anything' ($30,000 paint booth, etc)
I guess the DIY powder coating stuff from Harbor Freight isn't even available there?
There shouldn't be any volatile compounds with powder coat, unless you overheat parts as it's basically a thermosetting plastic 'covering' and the powder should be pretty inert? (although I'm sure someone can 'educate' me on the finer points?)
On a MIG, increasing wire feed increases amps. Perhaps you meant volts.

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Offline crazypj

  • Posts: 13454
  • Split personality, I fake being smart
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #149 on: Mar 26, 2018, 10:32:23 »
The piston clearance is fine, it isn't s 50 yr old V-8.
The '0.001" per inch of bore' is so outdated it isn't even funny anymore
 If you were using Wiseco you would need  more clearance as they use quite a soft, high expansion alloy.
 What surface finish did they put on it? I usually finish wit 400 grit hone and rarely bother with Flex Hone as 'extra' step.
Had one on dyno @12,000 rpm about 1hr after building motor, only got 2 'heat cycles before being beat on
Even in 70's Suzuki (and most others) were using higher quality high silicon alloy 'low expansion' pistons. I hesitate to say it, but, if you want some idea how strong they are, stand one on a flat surface and hit it with the biggest hammer you can find -14lb sledge hammer will work (basically what happens when you get pre-ignition or detonation) Will probably dent top but overall dimensions will be relatively unchanged. You won't need anything better than 93 octane, I think if you check with other 378 owners, 87~89 still works fine
« Last Edit: Mar 26, 2018, 10:35:25 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