Author Topic: CB750 K0 Front Sprocket Case Protector  (Read 1619 times)

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
CB750 K0 Front Sprocket Case Protector
« on: October 01, 2019, 03:48:49 PM »
According to John Wyatt, my 1970 CB750 K0 (Engine Number 1036****) should be fitted with a case protector (Part No: 11353 300 010) around the front drive sprocket, but it isn’t. Apparently, the front sprocket cover was modified at E1026144 to accept the case protector. I’m thinking my sprocket cover may be from an earlier bike, though I can’t find any pictures to show how they differ. Grateful if any of you could enlighten me.
Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline Trigger

  • Grogu
  • *
  • Posts: 8434
  • Engines built on reputation, not advertising.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #1 on: October 01, 2019, 05:39:03 PM »
Honda had a design problem on the early units. The chain would jump if loose and punch a hole in the crank case, honda came up with a case protector but all this did was push the protector through the crank case. After a lot of head scratching in the land of the raising sun, they found that putting a extra tooth sprocket solved the problem and did away with the protector.
There is a cut away in the sprocket cover so that it fits with a protector. Show me a pic of the top of the cover and I will tell you what type it is  ;)

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #2 on: October 02, 2019, 01:09:17 PM »
Hi Trigger,

Thank you for your knowledge and advice.

Attached are two pictures of the gearbox sprocket cover, on which I can see nothing to mount a sprocket case protector.

I note that my bike (E1036***) has been upgraded with 18-front and 48-tooth rear sprockets, introduced at Engine number 1044805. I also note that it has, as expected, the 'so called' adjustable chain oiler, introduced at E1026144, on the front sprocket. I imagine the sprocket case protector, that was introduced to cover the previous 17-tooth sprocket, may be too small in diameter to cover an 18-tooth?

Whilst trying to make my bike perfectly correct, it seems only sensible to retain the 18/48 tooth set-up and avoid disaster!
Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline Trigger

  • Grogu
  • *
  • Posts: 8434
  • Engines built on reputation, not advertising.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #3 on: October 02, 2019, 07:29:38 PM »
The protector does not mount on the sprocket cover, it bolts to the crank case.
Found one that was used with a protector, it is the one on the left and has a cut away. I have had many of these sprocket covers through my workshops over the years and some had a different cut away and looked like it was just cut at a work shop when they fitted a protector.

I would not take John Wyatt book as gospel, or anyone else's  ;) [ Guests cannot view attachments ]

Offline Trigger

  • Grogu
  • *
  • Posts: 8434
  • Engines built on reputation, not advertising.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #4 on: October 02, 2019, 07:31:16 PM »
The top mounts here



[ Guests cannot view attachments ]

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #5 on: October 02, 2019, 10:45:46 PM »
Hi Trigger,

Thank you for the description and photos showing the cut away and crankcase mounting point.

The sprocket cover on my bike does not have the cut away. It is as the one on the right in your photo.

I understand that, when the 18-tooth sprocket was introduced the case protector was deleted and a chain guide rubber (that mine has) was also added. It therefore seems logical not to fret over the absence of a case protector.

Your help in reaching this understanding is much appreciated.

Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline Trigger

  • Grogu
  • *
  • Posts: 8434
  • Engines built on reputation, not advertising.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #6 on: October 04, 2019, 03:20:35 PM »
Hi Trigger,

Thank you for your knowledge and advice.

Attached are two pictures of the gearbox sprocket cover, on which I can see nothing to mount a sprocket case protector.

I note that my bike (E1036***) has been upgraded with 18-front and 48-tooth rear sprockets, introduced at Engine number 1044805. I also note that it has, as expected, the 'so called' adjustable chain oiler, introduced at E1026144, on the front sprocket. I imagine the sprocket case protector, that was introduced to cover the previous 17-tooth sprocket, may be too small in diameter to cover an 18-tooth?

Whilst trying to make my bike perfectly correct, it seems only sensible to retain the 18/48 tooth set-up and avoid disaster!

All early units have the chain oiler, even sandcast units. It is the later units that did not have them so, I am not sure were you get E1026144 from  ???

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #7 on: October 04, 2019, 09:11:54 PM »
Yes they all had a chain oiler, but prior to E1026144 it used a felt plug that could not be adjusted. The latter oiler provided a screw to adjust the amount of oil (screw in to reduce), though of questionable effectiveness. I've got mine screwed right in to see if the chain drys.
Service Bulletin #30 expands.
https://www.dropbox.com/s/xkkwyl5lteti976/CB750%20Service%20Bulletins.pdf?dl=0
« Last Edit: October 04, 2019, 09:18:18 PM by StevieWonder »
Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline Trigger

  • Grogu
  • *
  • Posts: 8434
  • Engines built on reputation, not advertising.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #8 on: October 04, 2019, 09:40:31 PM »
Yes they all had a chain oiler, but prior to E1026144 it used a felt plug that could not be adjusted. The latter oiler provided a screw to adjust the amount of oil (screw in to reduce), though of questionable effectiveness. I've got mine screwed right in to see if the chain drys.
Service Bulletin #30 expands.
https://www.dropbox.com/s/xkkwyl5lteti976/CB750%20Service%20Bulletins.pdf?dl=0

I know as, I build SOHC's for a living  ;) But, the number is wrong as i have found non adjustable screw types up to E103's .

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #9 on: October 07, 2019, 08:39:51 PM »
I bow to your experience Trig. I'm quoting from the John Wyatt book again.

I note that the oil adjusting screw is quite loose and I'm not convinced it will stay as set, when the front sprocket spins up/down rapidly say for example if an engine was reved hard in neutral. What might I do to hold it in place without locking it?
Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline K2-K6

  • Grogu
  • *
  • Posts: 5232
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #10 on: October 07, 2019, 10:11:07 PM »
The sprocket doesn't rotate if it's in neutral and the final drive chain is connected,  else it'd be in gear  :)

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #11 on: October 08, 2019, 11:28:32 AM »
 :-[ :-[ :-[ of course a dumb example. But I'd still like to make the adjuster tighter - any ideas?

I'm thinking there is probably some sort of non-setting putty type compound, that would withstand the heat, a little of which added to the screw would make it tighter.
Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline K2-K6

  • Grogu
  • *
  • Posts: 5232
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #12 on: October 08, 2019, 04:03:01 PM »
I don't feel there's a real risk in loosing it,  non permanent loctite type compound would be obvious choice, though it would have to be degreased prior to that.

Generally most where deactivated in contemporary use as they make a real mess of the bike's rear end,  the engine oil is just not suitable out in the open and it flings everywhere.

Offline StevieWonder

  • SOHC Associate
  • Posts: 58
  • Oh, fast and shinny. Me like fast and shinny.
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #13 on: October 08, 2019, 06:03:25 PM »
I'm hoping to stop any engine oil flying around the rear by holding it in the fully closed position, then regularly apply proprietory chain lube.
Previous Bikes:
Honda S90
Honda CB125 Twin
Triumph T90
Honda XL250
Bombardier Can-Am 250
Honda CBX750

Offline K2-K6

  • Grogu
  • *
  • Posts: 5232
    • View Profile
Re: CB750 K0 Front Sprocket Case Protector
« Reply #14 on: October 08, 2019, 08:37:44 PM »
Sounds likely a decent choice.

Its funny that when they made that oil bleed system chainlube, as we now know it,  I don't think existed.  Maybe the boil-in-a-tin type but nothing spray on.

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal