collapse

www.dimecitycycles.com

https://www.townmoto.com/collections/vanson-leathers


www.restocycle.com

www.CITYLIMITMOTO.com

www.jadusmotorcycleparts.com

www.bisonmotorsports.com

www.speedmotoco.com

www.lostapostlejewelry.com

www.cognitomoto.com

www.sparckmoto.com

www.pistonsociety.com

www.steeltowngarage.com


Author Topic: 75 CB360 - bad omen "yatagarasu" build  (Read 27590 times)

Offline onefromexile

  • Posts: 267
75 CB360 - bad omen "yatagarasu" build
« Reply #250 on: May 12, 2018, 15:50:00 »
I may use this scale to check that out, they are different in diameter by a couple thousandths so when I gave instructions to machine shop for boring they bored a right and left differently
 One is probably lighter than the other
Well they should be slightly oval not exactly round the pistons
The bore should be exact
There is a reason I just canít remember exactly how to phrase it


Sent from my iPhone using DO THE TON

Offline MiniatureNinja

  • Posts: 480
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #251 on: May 12, 2018, 16:58:24 »
Should be a little pocket rocket when done  8)
Try not to hurt yourself  ;)
Me? Get hurt? I'm invincible! That's the 19 year old U.S. Marine talking

Now I'm 36 with kids...  I just really wanna beat my friends CB900 with this bike I know I can do it
'75 Honda CB360 - thread

Offline MiniatureNinja

  • Posts: 480
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #252 on: May 12, 2018, 19:06:29 »
I went with Arias on my build. 210g each. ;D

But then I broke them and swapped over to GS850s..   :(
If I remember from your HTn thread you did that because you were doing megacycles cam?
I forgot to ask what was all involved in getting that came. Why they needed a special piston, probably due to the amount of lift. I thought I would drop a megacycles cam and titanium springs in at a later date but I wont get to do that if the pistons need work too
'75 Honda CB360 - thread

Offline crazypj

  • Posts: 13199
  • Split personality, I fake being smart
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #253 on: May 12, 2018, 21:26:16 »
Me? Get hurt? I'm invincible! That's the 19 year old U.S. Marine talking

Now I'm 36 with kids...  I just really wanna beat my friends CB900 with this bike I know I can do it
If it's the 1979~82 CB900, find somewhere with several medium to tight turns with no long straights and he'll think he's riding a three legged camel (*if it's one of them, he is  ;D )They are a heavy lump to hustle through a series of twisties  ;)
'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: 480
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #254 on: May 12, 2018, 23:40:27 »
If it's the 1979~82 CB900, find somewhere with several medium to tight turns with no long straights and he'll think he's riding a three legged camel (*if it's one of them, he is  ;D )They are a heavy lump to hustle through a series of twisties  ;)

it's an 82 and it's been "cafe'd" out but as i learn about doing mine, not very well... just basic "cafe racer" stuff and no performance gains. much lighter than stock I imagine
where we raced last time is close to what you described, but there are 2 main sections of long straights he just pulled away so fast on

question, how much blu-tack should I get to check valve clearance? and can I do it with no valve springs in just valves closed and everything torqued down?
« Last Edit: May 12, 2018, 23:44:03 by MiniatureNinja »
'75 Honda CB360 - thread

Offline NvgtrWiggles

  • Posts: 172
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #255 on: May 13, 2018, 00:44:47 »
What do you mean by "pile" ? I'm always up for more parts!

6 mostly complete engines.

Offline MiniatureNinja

  • Posts: 480
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #256 on: May 13, 2018, 12:21:58 »
6 mostly complete engines.
Cool, I'd buy a spare complete! I'm always getting spare parts on Ebay just in case


Just about to do the valve clearance test on the engine when I get back from the store with some blu-tack or something similar. I assumed staples would have it. They don't.

Although I really dont know what to do if they are too close... maybe order new gasket?
'75 Honda CB360 - thread

Offline teazer

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 8732
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #257 on: May 13, 2018, 12:30:45 »
Well they should be slightly oval not exactly round the pistons
The bore should be exact
There is a reason I just canít remember exactly how to phrase it


Sent from my iPhone using DO THE TON

Pistons are thinner from side to side compared to front to back.  That's to reduce viscous drag in the same way that slipper pistons are designed but at a much lower cost of manufacturing.

They are also smaller at the top where they get hotter and expand more than at the bottom of the skirt where they stay cooler and expand less.

Pistons also rocks lightly and the bottom 1/2" or so tends to be more worn and that's why they tell you to measure a little way up from the bottom of the skirt.

And yes, pistons do tend to be slightly different from one to another, so your machine shop should always bore each side to match a particular piston and they should come back marker 1,2 or something similar.

Offline teazer

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 8732
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #258 on: May 13, 2018, 12:40:10 »
If I remember from your HTn thread you did that because you were doing megacycles cam?
I forgot to ask what was all involved in getting that came. Why they needed a special piston, probably due to the amount of lift. I thought I would drop a megacycles cam and titanium springs in at a later date but I wont get to do that if the pistons need work too

"hotter" cams usually have more lift and more duration (held open for longer), so they tend to need more piston to valve clearance than a stock cam.  Some motors have enough clearance to get away with hotter cams, but some are tight stock and need valves to be recessed slightly or pockets cut in the piston crowns - or both if you mill the head and fit race cams.

The process is simple but tedious.  You build the motor with light valve springs and gently turn it over to see when the valves touch the pistons and then back off the valve adjustment until it just turns over.  Then you calculate how much valve clearance you have when the valves are closed and that's a starting point for how much to cut the pistons or head.

You want about 40 -60 thou clearance between valve and piston at the point they are closest to each other and obviously there must be clearance between the valves which can be an issue when fitting large valves.

Repeat until you have sufficient clearance and then assemble the motor for real.

With race motors, that's just how it goes.  With mid cams there may be sufficient clearance if you get lucky.  Sometimes the motor clicks as it runs when pistons touch the valves and then it's motor out time again.   

Offline crazypj

  • Posts: 13199
  • Split personality, I fake being smart
Re: 75 CB360 - bad omen "yatagarasu" build
« Reply #259 on: May 13, 2018, 13:46:29 »
Use modeling clay or Play Doh to check clearance. Michaels, ToysRUs, etc With pistons, the extra mass around gudgeon pins expands more than thinner sections which is another reason 'sides' are reduced diameter. If your pistons are sticking out 0.010", you use a 0.050" head hasket or next thicker one. You want around 0.035"~0.040" piston to head clearance
« Last Edit: May 13, 2018, 13:50:24 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