« previous next »
Pages: [1]   Go Down

Author Topic: Big bore cylinder air passage  (Read 2054 times)

0 Members and 1 Guest are viewing this topic.

Offline afkrejci90

  • Enthusiast
  • **
  • Posts: 192
Big bore cylinder air passage
« on: July 14, 2015, 09:10:44 PM »
Getting my block installed with new sleeves for 72mm pistons, I got a call from APE about the possibility of breaking through the air passage.  Figuring I'm not the first to install a kit this big, has anyone had an issue with oil leaks?  Is there any remedy for this?
Logged
'78 CB750K http://forums.sohc4.net/index.php?topic=105327.0
'80 CB750C - Sold
'06 CBR600RR

Offline Jerry Rxman Griffin aka MuthaF'er

  • This MuthaF'er is getting to be a
  • Really Old Timer ...
  • *******
  • Posts: 14,902
  • Bought her new 4/75
Re: Big bore cylinder air passage
« Reply #1 on: July 14, 2015, 10:28:34 PM »
Sure there have been oil leaks. Jay did mine at APE. 71mm kit. He filled the openings in the block with epoxy. I have not run it yet however. I'll keep my fingers crossed.
Logged
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: Big bore cylinder air passage
« Reply #2 on: July 14, 2015, 10:46:03 PM »
Yeah they can be leaky..If the sleeves are showing..it's prone to leaks..
Logged
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Big Jay

  • Expert
  • ****
  • Posts: 1,252
    • CBRzone
Re: Big bore cylinder air passage
« Reply #3 on: July 14, 2015, 11:57:46 PM »
These are larger sleeves are larger than what we use. They will break thru into the air passages.
Logged

Offline afkrejci90

  • Enthusiast
  • **
  • Posts: 192
Re: Big bore cylinder air passage
« Reply #4 on: July 15, 2015, 09:42:33 AM »
Jay, will your sleeves be the better option to go with here?
Logged
'78 CB750K http://forums.sohc4.net/index.php?topic=105327.0
'80 CB750C - Sold
'06 CBR600RR

Offline Big Jay

  • Expert
  • ****
  • Posts: 1,252
    • CBRzone
Re: Big bore cylinder air passage
« Reply #5 on: July 15, 2015, 02:25:38 PM »
Alex;
Your pistons are 71.2 mm, an odd size.  Our sleeves were designed for 71mm max. I did the math and would have a .065" wall thickness. I really don't line anything under .075, .070max.   We can do it if you want. I hope you got rings to go with the odd size piston.

Logged

Offline afkrejci90

  • Enthusiast
  • **
  • Posts: 192
Re: Big bore cylinder air passage
« Reply #6 on: July 15, 2015, 02:36:30 PM »
Yes these were custom from JE so I have everything needed.  I really have no other choice but having these put in and epoxied. 

Just to clarify because I'm not too familiar with this, where is the break through on the cylinders?

Would brazing be better than epoxy due to the thermal characteristics?  I would think epoxy would warm up slower than aluminum and eventually break the bond.
« Last Edit: July 15, 2015, 04:42:37 PM by afkrejci90 »
Logged
'78 CB750K http://forums.sohc4.net/index.php?topic=105327.0
'80 CB750C - Sold
'06 CBR600RR

Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 19,839
  • Saver of unloved motorcycles.
Re: Big bore cylinder air passage
« Reply #7 on: July 15, 2015, 03:36:32 PM »
 Between the fins
Logged
No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.

Offline cbr954

  • Hot Shot
  • ***
  • Posts: 402
Re: Big bore cylinder air passage
« Reply #8 on: July 15, 2015, 05:35:31 PM »
I had a small seep even with the APE sleeves, ended up having to silicone the gap shut, though it isnt a permanent fix but it is working right now.  Cycle X will weld the gaps shut then bore them out for the new sleeves if it looks like they will break through.
Logged
03 CBR954RR, 72 750 chopper(970cc
F2 head), 2017 CRF450R, 2001 CR250R, 72 CB500, 79 XR250, 04 CRF50,70's soon to be rebuilt cb750 drag bike.

Offline bear

  • Vale Bill McIntosh ......"illegitimi non carborundum"
  • Old Timer
  • ******
  • Posts: 2,575
  • Leeton in Australia
Re: Big bore cylinder air passage
« Reply #9 on: July 15, 2015, 05:57:16 PM »
We use 72mm+ pistons in our race motors.
I would suggest you have them welded before removing the original sleeves by someone who knows what their doing.
Jim F would be the man I would think.
We used to use epoxy but the results where a bit hit and miss.

Cheers,
Brian
« Last Edit: July 15, 2015, 06:16:38 PM by bear »
Logged
The older I get the faster I was.

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: Big bore cylinder air passage
« Reply #10 on: July 15, 2015, 08:02:42 PM »
 I think what they may do is bore it out 90per cent..weld up any holes,  then finish bore and hone....for the best results.. But it adds cost...
Logged
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline scottly

  • Global Moderator
  • Really Old Timer ...
  • *****
  • Posts: 16,268
  • Humboldt, AZ
Re: Big bore cylinder air passage
« Reply #11 on: July 15, 2015, 08:40:54 PM »
You may want to consider one of Mike's billet cylinder blocks:
http://forums.sohc4.net/index.php/topic,49438.625.html
Logged
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline bear

  • Vale Bill McIntosh ......"illegitimi non carborundum"
  • Old Timer
  • ******
  • Posts: 2,575
  • Leeton in Australia
Re: Big bore cylinder air passage
« Reply #12 on: July 15, 2015, 09:13:44 PM »
Quote from: scottly on July 15, 2015, 08:40:54 PM
You may want to consider one of Mike's billet cylinder blocks:
http://forums.sohc4.net/index.php/topic,49438.625.html



No doubt the best option if the budget stretches.

Our solution is pictured below.

Mike's cylinders are a few steps further along the development path.

Cheers,
Brian



 


« Last Edit: July 15, 2015, 11:10:16 PM by bear »
Logged
The older I get the faster I was.

Offline Big Jay

  • Expert
  • ****
  • Posts: 1,252
    • CBRzone
Re: Big bore cylinder air passage
« Reply #13 on: July 16, 2015, 10:47:25 AM »
Alex;

Have you seen the e-mail from Mike at APE?
Logged

Offline afkrejci90

  • Enthusiast
  • **
  • Posts: 192
Re: Big bore cylinder air passage
« Reply #14 on: July 16, 2015, 04:03:03 PM »
Quote from: Big Jay on July 16, 2015, 10:47:25 AM
Alex;

Have you seen the e-mail from Mike at APE?
Not yet, I pm'd you the correct email just in case.
Logged
'78 CB750K http://forums.sohc4.net/index.php?topic=105327.0
'80 CB750C - Sold
'06 CBR600RR

Offline afkrejci90

  • Enthusiast
  • **
  • Posts: 192
Re: Big bore cylinder air passage
« Reply #15 on: July 16, 2015, 10:27:05 PM »
Quote from: scottly on July 15, 2015, 08:40:54 PM
You may want to consider one of Mike's billet cylinder blocks:
http://forums.sohc4.net/index.php/topic,49438.625.html

As much as I would like to get one of those blocks, I'm afraid it would just be a budget buster  :(
Logged
'78 CB750K http://forums.sohc4.net/index.php?topic=105327.0
'80 CB750C - Sold
'06 CBR600RR

Offline Medyo Bastos

  • Master
  • *****
  • Posts: 1,582
  • Gusto mo titi ko?
    • project
Re: Big bore cylinder air passage
« Reply #16 on: July 17, 2015, 04:24:38 AM »
i have a freshly bored and honed RC BIG BLOCK 73mm


...Save a tree, eat a beaver...
Logged
Pages: [1]   Go Up
« previous next »