Topic: Is this fixable?

[arncruz]

I have a cb750 engine with a hole in the crankcase and top left posterior engine mount is missing from the top  crankcase. Looking for some advice at to how to fix this or if anyone has had this problem before.  Any advice would be greatly appreciated.
thanks
arnold

[754]

Its a sandcast, definitely worth fixing.
But choose the welder carefully, and check his previous work.
Is the right side motor mount in the pic cracked?, any other case damage like  the point area,
Try getting missing mount from another moter then retexturing the area.

[arncruz]

Thanks for the quick response and recommendations.  As far as the broken engine mount, do you think I could use a later model engine to supply the missing area? 

[markreimer]

Definitely fixable. My K4 has a repair in that exact spot. I didn't even know about it until a few years after buying it, and putting lots of miles on it. I was cleaning all the chain lube junk out of there and discovered the repair! Don't loose heart, get it welded up and ride!

[754]

Yes, but you have to rework it to make it match.
I may be able to get some bits from a diecast engine..

[arncruz]

thanks Calj737 for the details.  I figured it's gonna be a costly repair.  I'll have to price it out and see if the machinist can do this type of repair before I dump all this money into the project.

[754]

Look around , many welders can stick it together,  but only a few can do the job to the level that needs to be done to retain its value, either way, if you don't fix it and end up selling it, someone will fix it.
 To be brief, don't rake the convenient fix, take the proper fix.
My buddy had pretty good luck, re texturing smooth casting to look like sandcast...

[SOHC4 Cafe Racer Fan]

How does the rest of the bike look. Being a sandcast is definitely the tipping point here.  That will be a tricky repair.

[arncruz]

Unfortunately it's not complete.  All I have for this project is the frame and engine.  But I do have parts from a 1969 parts bike including a wrinkle tank and 4 into 4 unstamped exhaust, side cover, wiring harness, hand controls, and front end

I also have a question for the sandcast experts.  Do the numbers on this engine appear thin to you compared to other sandcast engine number.  Could this be a replacement engine with a stamped number on it?  Also,  is it possible to have a replacement unstamped engine that is also a sandcast?
I put a collage of the other two sandcast engines that I had. This broken one does look different - so I'm thinking it is a replacement engine.

Thanks
arnold

[Stev-o]

  I'll have to price it out and see if the machinist can do this type of repair before I dump all this money into the project.

Obviously, def worth trying to save. 
I would go on the SOOC forum to find recommendations for a welder.
There must be someone who has had this issue before, they should know...

[danyo]

Arnold, check how many screws for clutch cover you have. If sandcast, should be 9. Your broken cases looks like diecast. Font is not correct for factory Honda so it was replacement for sure. Also they replaced correct #8 bolts. Do you have cylinders and head for that motor?? I'm worried your engine could be newer model restamped to match old numbers. Please provide pic with view on top of the case. If diecast will be easy to recognize.

Sent from my SM-N900T using Tapatalk

[arncruz]

I agree Danyo.  Thanks for the input and expertise.   The font is not correct on the stamp and it's different from my other sandcast engine.   That is why I was questioning the engine case.  What probably happened was that the engine was replaced and then stamped with the engine number that was originally there.  Nonetheless, i'll keep the frame and put my other sandcast engine into it.  I can try to fix this case but now that i know it's a replacement, i'll just hold onto it for now.