Repairing CB77 Cylinder

G-Man · Post by **G-Man** » Sun Jun 12, 2011 7:09 am

When I got my CB77 project, the engine had been seriously waterlogged and I did some damage to the barrel trying to get the engine apart. The damaged barrel will form part of a 'big-bore' kit I am making with modified CB750 liners and CB350 pistons. I bought a second-hand CB77 barrel with nice liners but only realised that it had damage when I started to clean it up. The PO had left the camchain too loose and it had worn through the oilway at the front of the cylinder...

I thought that I could repair this with aluminum solder but I was worried about blocking the oilway. I set the barrel up and drilled out the oilway plugs so that I could slide a stainless steel 'chill' inside the hole to keep the passage way open..

With that done, I could slide the bar in to partially block the hole.

I abraded the area around the damage with my dremel and set the barrel up on some insulating bricks to help keep the heat in. It took a while to heat up but I was able to eventually get the barrel up to temperature for the aluminum solder. You have to get some solder onto the piece and then abrade the oxide layer through the molten solder with a stainless steel rod. This allows the solder to wet through the oxide layer.

Another session with the dremel gets rid of the rough edges and checks adhesion to the aluminum barrel.

I'm quite pleased with the result here but the next step is to do a little pressure testing to check for leaks, clean out the oil passages and then make some new plugs to seal everything up again.

rpr851r · Post by **rpr851r** » Sun Jun 12, 2011 7:59 pm

Nice repair. I have been eying that aluminum solder and was wondering how well it works.

G-Man · Post by **G-Man** » Mon Jun 13, 2011 1:28 am

It's really good stuff for the amateur workshop. Quite easy to work with and easy to machine or file afterwards.

I've used it to put fins back on barrels and heads. The biggest problem is getting the heat into a part like a finned cylinder as they are designed to dissipate it.

I lagged this one as much as I could and cleaned the surface completely with a burr in my dremel.

G