ewazix
CB750 Member
I have the Honda workshop manual & Haynes and read up on this but am confused... help appreciated please.
I'm rebuilding the engine of my 1979 CB750 RC01 low mileage barn find, that had apparently been rebuilt 20 years ago, run briefly and abandoned. I've found lots of good things, including rebored and oversized pistons, new looking chains and guides, straight crank, fresh looking bearing shells, everything measuring to spec. BUT No1 has a bent conrod! I'm assuming it may have hydrolocked, been rebuilt with the bent conrod, run badly and been abandoned.
Anyway, I have BBBB stamped on the lower engine case, A B B B A (1-5) crank pin codes on the bottoms of the crank lobes, but no other codes visible on the crankshaft. The conrods are all weight code 3 fitted with Black(1)-Brown(2)-Brown(3)-Black(4) bearing shells.
I was hoping to find a single replacement conrod of the same weight code 3 is this going to work? or a set, if so how do I work out what conrod part number (they are offered as A B C D E F part No 13201-425, 13202-425 etc in parts catalogues, but no mention of these in the manual) and what bearing shell combination? I just cant get my head around it. Also will conrods from other bikes in that year series fit e.g. the F?
I hope someone can help please, go easy
Edit / update. By a process of measuring all the crank main and pin bearings I've finally worked out what I have by putting them on a table, it was the only way I could get my head around all the cross-codes for the bearings!
I've sourced a complete crank and con-rod set that look to be in good condition so should be able to renew all the bearing shells and get on with the build.
I'm rebuilding the engine of my 1979 CB750 RC01 low mileage barn find, that had apparently been rebuilt 20 years ago, run briefly and abandoned. I've found lots of good things, including rebored and oversized pistons, new looking chains and guides, straight crank, fresh looking bearing shells, everything measuring to spec. BUT No1 has a bent conrod! I'm assuming it may have hydrolocked, been rebuilt with the bent conrod, run badly and been abandoned.
Anyway, I have BBBB stamped on the lower engine case, A B B B A (1-5) crank pin codes on the bottoms of the crank lobes, but no other codes visible on the crankshaft. The conrods are all weight code 3 fitted with Black(1)-Brown(2)-Brown(3)-Black(4) bearing shells.
I was hoping to find a single replacement conrod of the same weight code 3 is this going to work? or a set, if so how do I work out what conrod part number (they are offered as A B C D E F part No 13201-425, 13202-425 etc in parts catalogues, but no mention of these in the manual) and what bearing shell combination? I just cant get my head around it. Also will conrods from other bikes in that year series fit e.g. the F?
I hope someone can help please, go easy
Edit / update. By a process of measuring all the crank main and pin bearings I've finally worked out what I have by putting them on a table, it was the only way I could get my head around all the cross-codes for the bearings!
I've sourced a complete crank and con-rod set that look to be in good condition so should be able to renew all the bearing shells and get on with the build.
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