Topic: crack in case where cases join :( need advice

[thomellis]

alright, well, looks like I've got my first big issue.  As I was taking the last few bits off the case so I could get it cleaned and repainted, underneath years of caked on oil and dirt, I noticed I have a good size crack in the case here.

I've seen a lot of people have had good luck with jb weld and alumiweld, but I'm worried about this one as it's right where the 2 cases join.  There's actually two cracks.  One is on the post for the case bolt, the other, and bigger one is in the back.

Originally I didn't plan on splitting the cases, but it's looking like that might not be avoidable now as I don't want to weld the cases together

Anyone have any good ideas?  Or is this something I'm going to have to strip down and take in to get properly welded and fixed?

Thanks in advance for any help and advice...







sad day

[CycleRanger]

alright, well, looks like I've got my first big issue.  As I was taking the last few bits off the case so I could get it cleaned and repainted, underneath years of caked on oil and dirt, I noticed I have a good size crack in the case here.
sad day

Aaugh, I'm having a flashback! 

Been there, only mine was worse.
Yours is a candidate for repair, imho.
If the bike is currently running well and you weren't already planning any major engine work I'd probably JB weld it and ride it until the leak gets to bad to tolerate..
Welding, as you know, would pretty much require a tear down.

[thomellis]

Thanks cycle, sorry to hear you've had the same experience   There's some grooves in the case, so my best guess is the chain snapped at some point in the past and just cracked the case.  I initially didn't want to dive all the way into the case mainly just because I wanted to get things back together and ready to ride.  Everything was running pretty well before, the main reason for the breakdown was to fix some small oil leaks...this looks like it was one of em...

Decisions, decisions...

[CycleRanger]

Yes, there are several threads about this exact type of case damage and various resolutions.
Mine was much worse than yours and had been patched before I got the bike and later started leaking.
I happened to luck onto a good replacement engine so the original engine is under the bench now waiting to get a new lower case in the future.
From your pictures I think yours would a good candidate for JB weld for now.

[754]

Get it clean and patch it, may work for years.. Dont split the caases unless you enjoy the extra work right now or have some other reason to split them...

[MoMo]

Another vote for JB Weld...Larry

[thomellis]

Thanks for all the feedback guys.  JB sounds like it might be the way to go.  I'd much rather go the JB route since it would get me back on the road quicker, but at the same time, if I'm putting all this work in, I don't want to get it all back together for it just to drip oil still.  Is the JB weld going to be strong enough to fuse the two cases together, or will I be able to break it in the future?

Also, I just found out a buddy of mine has an old cb750 engine lying around (I think it's a '75), any chances there weren't any changes to the lower case between 72 and 75?  Of course this would mean I'd have to split 2 cases...

[Harsh]

Welding the cast aluminum if difficult.  Cast aluminum inherently has air pockets which causes mini "explosions"  You really won't get a nice bead if you get a bead at all.  You might be able to get away with JB, but if it were me I would be looking for a new lower half or just use the entire engine that your buddy has.

[MoMo]

From what I remember, the cases are matched. We always replaced the entire top and bottom when the type of damage you have required repair. At the time we were allocated roughly 18 hours of flat rate time...Larry

[CycleRanger]

If you want to replace the case you'll have to replace both the upper and lower halves as they are matched when machined at the factory.
Also, changing the cases would very likely require new main bearing shells at the least.
Any competent welder should be able to solidly weld that but it would require removing the lower case.

[bryanj]

Look carefully,

Not only is it cracked but also pushed in, which makes a gap in the join between the crancase halves.

A repair with epoxy will hold for quite some time AS LONG AS you clean all the oil and grease from the area first and you should still be able to do a proper welded repair when the cases are split

[thomellis]

Thanks everyone for the replies, lots of good info and advice.  I'm going to start calling around and see how much it would cost to get it welded if I split the cases and try to figure out if it's worth the trouble or not, otherwise I'll try the JB route and see how long she will last.

[CycleRanger]

If you do decide to have it welded at least it looks like the damage is confined to the bottom half which can be removed and replaced without having to completely take apart the lower end.

[Danno]

a professional tig welder could fix that in about ten minutes or someone that knows how to aluminum solder but the tig welding would be the best repair and no more material would have to be removed to do it
 
both types of fixes are permanent and never worry again repairs 

jb weld in this instance may work fine if you can get the mating surfaces clean enough which is the same problem soldering it would have

[grcamna2]

Welding the cast aluminum if difficult.  Cast aluminum inherently has air pockets which causes mini "explosions"  You really won't get a nice bead if you get a bead at all.  You might be able to get away with JB, but if it were me I would be looking for a new lower half or just use the entire engine that your buddy has.

I'd get that other engine from you're buddy when you can and see what it needs & install it in you're bike;replace the one you have and sort out the fresh engine with good cases.The cases you have may have been damaged to the point where it could keep the case halves from sealing 100% in that area in the future.

You may be able to repair you're Original engine's cases...but it could be labor intensive.