73 CB750 Engine cases

[frogwash]

I am looking for the lower half of the crankcase. Upper half is usable but the lower half has a chunk out of it where it appears the chain has maybe broke and doubled up in front of the sprocket.. I purchased this bike that has been sitting for probably 40 to 45 years in a barn.

I have found a couple of cases on EBay but thought I would try here... They don't appear to be in bad condition but would like to purchase from someone who knows these bikes.

I actually had a 1972 in 1972! Had it for about 3 1/2 years before it was stolen in California. The person(s) who took it had no idea what they were getting in a large u-haul. Everything we owned was in it. They broke it loose from the car we were hauling it with in the middle of the night while I was in the hotel room sleeping.... Had an 18 month old son and all his stuff was in there of course... everything... gone. My pic is the bike I built with that 73 engine and that is the bike that was stolen

Would appreciate any leads to this part!! Thanks

 

[dirtdigger]

You have to get a matched set of cases. The bearing bores are machined in the cases as a set, you cant swap case halves.

 

[frogwash]

Forgot about that.... thanks... got a set??

 

[dirtdigger]

None to sell. There are quite a few sets on ebay right now.

 

[wwsummers]

what year? 77/78's are different than 69-76 ( some internals different too). where are you? I am in Texas & have numerous seized engines & several 77/78 cases I just disassembled.

 

[frogwash]

what year? 77/78's are different than 69-76 ( some internals different too). where are you? I am in Texas & have numerous seized engines & several 77/78 cases I just disassembled.

Mine is a 73....

 

[frogwash]

None to sell. There are quite a few sets on ebay right now.

Mine is a 73....

 

[frogwash]

Oops.. I am in Twin Falls Idaho. There are a couple on EBay but nothing I am crazy about. Had a welder take a look at it today. I wasn't optimistic knowing welding like I do. But thought I would give it a shot... castings are not good candidates for any welding.

 

[dirtdigger]

They have been welding these cases since the bikes came out and broke cases. No its not the best but a decent welder can do it. Just dont weld all at once or the case can warp. Just look at all the welding that have been done to modify the cases in drag bikes. Can be done, good prep and a guy that knows what he is doing can make it work well.

 

[frogwash]

The piece that has been removed is not only very large but also in a precarious spot... also not crazy about the stress in that area. Plus now the cases need to fit tight in that spot as well to prevent an oil leak.

 

[wwsummers]

Mine is a 73....

I have pre-77 engines, but all seized except one & require disassembly. Strip down for cases $175. Complete seized engines $300 & non-seized $375 (no case damage). Latter two will need rebuilding. Would offer to rebuild for you (top end our complete) but working on a build for a friend now then of to my retirement projects. Again, in Texas.

 

[wwsummers]

The piece that has been removed is not only very large but also in a precarious spot... also not crazy about the stress in that area. Plus now the cases need to fit tight in that spot as well to prevent an oil leak.

Looking at pic, I Think I've already been talking to you in FB groups.

 

[frogwash]

I have a complete engine. Getting the barrels bored as we speak. Have new slightly oversize pistons. Ordered a new gearset for trans that had some rust due to sitting in water for so long. Ordered a total carb rebuild kit. Valve work next. All new seals. This is not my 1st rebuild. My 1st one was in 1975. It was a '72 engine. I popped that one out to 836. Crank and rods on this are in excellent condition. Just need cases. FB? If you mean Facebook I am not on that. Must be someone else with the same issue. Thanks but I need to keep cost down on this build. Don't need a complete engine, running or not. Thanks!

 

[dirtdigger]

Obviously different cases are best solution. Have seen worse breaks fixed! But if you can find a set of cases thats best.

 

[frogwash]

It would probably cost me just about as much to get it welded as it would to get a new set of cases. At least a different set of cases will will give me a better seal around that area, that's for sure!

 

[wwsummers]

I have a complete engine. Getting the barrels bored as we speak. Have new slightly oversize pistons. Ordered a new gearset for trans that had some rust due to sitting in water for so long. Ordered a total carb rebuild kit. Valve work next. All new seals. This is not my 1st rebuild. My 1st one was in 1975. It was a '72 engine. I popped that one out to 836. Crank and rods on this are in excellent condition. Just need cases. FB? If you mean Facebook I am not on that. Must be someone else with the same issue. Thanks but I need to keep cost down on this build. Don't need a complete engine, running or not. Thanks!

lemme know if only only want cases for 70-76 or 77-78