Engine O-Ring __HELP__

[Tronco]

Hello people!

I need your help.
I've seen this O-ring between the engine body, and when I took it out, it broke by itself (30 years old).

The problem is that I can not find the part, to be able to change it.
It doesn't appear in the diagrams of the web pages of purchase.
For example:
https://www.cmsnl.com/honda-cb750f2-1982-c-general-export-kph_model14880/partslist/E13.html#results


Anyone know where to find this O-ring?


This is the upper side


Thanks in advance!
Tronco

 

[Dave]

My shop manual doesn't show an O-Ring there. It was probably added later and some obscure service bulletin was published for the change.

Just measure it and buy a match.

 

[Tronco]

I will try this...

Thanks!!

 

[amc49]

NOTHING goes there, an o-ring put there can cut off oil to one end of your primary shaft!

LOOK, the oil passageway in the third pic clearly shows the oil has to go somewhere. An o-ring across that cuts the oil supply off.

It means somebody has been inside engine before. Not a smart somebody either.

Been awhile since I had to chase oil control down on these but thinking maybe oil control orifice part #3 in the above parts link may press down into that hole to limit the oil getting to that bearing. Some of the supply points there are orifice limited to keep pressure up in the system and the things supplied don't require a whole lot.

The transmission oil supply is pressure restricted in the same way too.

 

[amc49]

Ack.................my bad.

 

[Tronco]

Then that means I have to remove that O-Ring, right?

For that reason also does not appear in the manuals.

Thanks a lot!

 

[Chris in Dorset England]

Take a look here
https://www.cmsnl.com/honda-cb750f2-1982-c-england_model14882/partslist/E15.h

 

[Tronco]

It's not there... I saw every part list of every page... I didn't found.

 

[Chris in Dorset England]

try this https://www.cmsnl.com/honda-cb750f2-1982-c-england_model14882/partslist/E15.html#results items 33 and 28

 

[Chris in Dorset England]

sorry finger trouble

 

[Tronco]

Hi Chris!
That O-Rings are from other parts... that part:

And other that I don't have pictures...

Thanks!!

 

[amc49]

Post #11 is correct...........other parts. Remove the one concerned o-ring and leave it out, you can clearly tell there is none there as one side of the case is not machined smooth (pic #3), rather dimpled as in sand casted in the circle. When (EVER) did you ever see an o-ring sealing point that was ROUGH, they aren't, o-rings are not intended to seal on a rough surface. Another dead giveaway is that the o-ring there is not thick enough to cover all the way across the thickness of that circular cutout too. The main one is that the o-ring cuts off what is clearly an oil passage to that end of the primary shaft, one of the bearings.

I'd be looking at how loose that bearing is on that end for sure, but there is some oil splash going on there anyway and it might be OK.