Topic: The Humanity! The Horror! Disaster.

[gregimotis]

Haven't posted much since the old forums... glad to be back (I guess ).

76 CB750f1

The Problem:

Last week the chain snapped.  As the chain ran off the sprockets onto the road, it slapped the rear of my transmission case and blew off a half-dollar sized piece of Aluminum.  That chunk is still in place, probably resting against whatever is in there, and the break is quite clean - if I pull it into place it completely closes the hole.



The Plan:

Pull the engine, clean the area and inspect for more - specifically internal - damage.  Stick the metal peice where it should go and apply Fat Wads of JB-weld or similar substance.  Change the oil a couple times to get whatever particulate might have found its way inside the machine.


The Questions:

1. I've heard of this sort of thing being done with JB-weld, has anyone ever actually used it and is it any good?

2. About how much clearance do I have behind that wall and the mechanical parts?

3. besides my leaking head gasket, is there anything I really should do/change as long as the engine is out anyway?  I'd really rather not fix what ain't broke, but I don't want to pull her out twice either.

3. If I end up replacing the whole case.... well, lets not think about that right now.

4. please add any thought you have on the subject





On the upside, my chain now gets lots more oil than it used to.

[KB02]

Right now I am at the end of a rebuild/build up of a 76 CB750F and I had a simular problem with the crank case. The chain ahd bound up and cracked the whole casing right in front of the front sprocket. On the inside, I had about 1mm of clearance of the transmision gears. I'm not sure if the 400 is the same as the 750 as far as lay-out goes, but it would be worth checking to see how far in you can push it (without loosing it) to check your clearance.

I had my whole engine apart anyway, so I just had mine welded.

If you're going to pull the engine anyway, you might want to consider dropping the lower pan to check it out. If you really don't want to go into that, ther JB should do a good job. You'll jjst want to inspect it every now and then to make suire it's still holding.

Tough luck, though, man. That really stinks.

[gregimotis]

I found a well recomended motorcycle shop and the owner says they will weld it if I bring in a clean engine.  I willl probably go that way, although leaving it in someone elses hands makes me nervous.

Further inspection, it looks like a couple milimeters of clearance, as kbo2 says.

[Buffo]

If you can you should look for the best welder you can find, most likey he is not working at your honda shop. I ALWAYS go to a guy down here who welds on boats and airplanes. He costs a little more but there is a HUGE difference in the work he does and other welders that I have used.

Don

[Bobby]

I agree with Don.  I use a guy who is missing teeth, has a terminal arc-weld sun burn and wears a coon-skin cap.  He isn't much to look at, but he takes enormous pride in his work.  Every town/county has a guy with a dirty shop, but does exeptional work.  Ask around.   These guys also love rescuing vintage machines.     

[Buffo]

My guy has all his teeth but got his big right toe cut off while welding on a oil rig. 

Yeah..he always wears this leather welding cap...always
.
Don