Topic: CB750 Broken case Need advice

[rtbmrgl]

Just discovered this on a 1976CB750 I just bought.
Here is a pic of the busted case, someone added a piece of sheet metal with JB weld and silicone to cover the hole. The bike has been driven quit a bit but developed a small oil leak.

Advice, opinions.

Has anyone tried this, Durafix or Hts-2000 Aluminum Repair, here is a youtube explaining.
HTS 2000 Aluminum Repair

Durafix
Durafix Aluminum Welding Rods

[Stev-o]

Looks like your bike suffered the broken chain syndrome.  Many guys have repaired the leak with different methods including JB Weld and aluminum welding. 
First thing I would do is clean it up real good.

[rtbmrgl]

Yeah the old chain in the case thing.
I've owned motorcycles all my life and like some of you I probably have had as many bikes than I am old (60yo) and I've never had any chain problem, even with all my Goldwings(hehe ) so I'm sure its from lack of maintenance. Its a shame.

I'm taking the engine out first, I have been doing a little research and so I might try the aluminum rods but ill do some practice first. I'm not worried, Ill get it fixed
thanks for getting back.
I just bought the bike, posted in project shop.

[HondaLover77]

I only had that problem once and It broke down on me on a busy street in Orlando, Thankfully it didn't do anything to the engine or anything else... Good luck on getting it fixed... It is a shame that the guy who had it before you didn't take care of it!! Keep us posted on your progress.

[seanbarney41]

I have fixed that with JB Weld, engine in the bike, rode it 300 miles the next day, and about 15k more, never leaked again...you just gotta clean very well and ruff up the aluminum...not that this is the best or only way to repair this problem

[faux fiddy]

Yeah the old chain in the case thing.
I've owned motorcycles all my life and like some of you I probably have had as many bikes than I am old (60yo) I just bought the bike, posted in project shop.

Uhh... At what point do I need a 'hoarder' diagnosis.  The sh8 goes downhill, the projects pile up. The city wants taxes to patrol your backyard. Just where I live I hope.

[rtbmrgl]

A

Yeah the old chain in the case thing.
I've owned motorcycles all my life and like some of you I probably have had as many bikes than I am old (60yo) I just bought the bike, posted in project shop.

Uhh... At what point do I need a 'hoarder' diagnosis.  The sh8 goes downhill, the projects pile up. The city wants taxes to patrol your backyard. Just where I live I hope.

Actually I only own three bikes, V-strom, CB500 and the newly acquired 750. I do have a shed full of Honda S90, CL90 parts going on Craigslist.

[rtbmrgl]

Hello again,

Is the easiest was to get CB750 engine out of the frame by laying on side and lifting frame off the engine?

[Stev-o]

Hello again,

Is the easiest was to get CB750 engine out of the frame by laying on side and lifting frame off the engine?

Yes, and easiest way to install it to.  Be sure to lay down padding on the ground to protect engine, moving blankets work great.

Here is a good read on it....

http://forums.sohc4.net/index.php?topic=39702.0

[rtbmrgl]

perfect, does the valve cover have to come out?

[Jay Ace]

I've discovered the same on mine when I was changing the chain and front sprocket.
Cleaned up the area and noticed that it has been fixed. No leaks that I could find.

[boatsdickson]

Coulda been worse....a rag jammed between the sprocket and case can be just as damaging as a busted chain. Nuthin like removing the chain and seeing your gears lookin back at ya.

[scottly]

I patched my welded, but leaky cases, with the motor still in the frame. I cut a scrap piece of aluminum to fit well beyond the leak, and after cleaning with brake cleaner, glued it into place with a liberal amount of silicone.

[rtbmrgl]

Coulda been worse....a rag jammed between the sprocket and case can be just as damaging as a busted chain. Nuthin like removing the chain and seeing your gears lookin back at ya.

Holly crap I though mine was bad.

[rtbmrgl]

I patched my welded, but leaky cases, with the motor still in the frame. I cut a scrap piece of aluminum to fit well beyond the leak, and after cleaning with brake cleaner, glued it into place with a liberal amount of silicone.

When you repaired it did the scrap piece cover over where the cases split. I might cover that area to make the repair and if I have to split the case ill have to cut it.