Topic: '77 550F cracked case

[d_benet]

Hi all,
I found a crack in my lower case; left rear corner on the radius between the engine mount and the oil pan mating surface just (see pics). I did a bit of searching and found this old thread where a couple of members found casting flaws similar model/years in what appears to be the same location: http://forums.sohc4.net/index.php?topic=118879.0 Mine unfortunately is definitely a crack, possibly up to 1/32" wide and seeping oil. My questions are: 1) Has anyone seen a cracked case here before? Seems like most incidents are resulting from broken chains. 2) What could have caused this? Being near the engine mount has me suspicious. 3) Is it repairable either with JB weld or TIG? There is an expert aluminum welder here and I was going to take it to him for an estimate. 4) Would I need to do a whole disassembly to have it welded? Seems like with the pan off, he would have reasonable access to the whole crack...but am I missing something? Thanks for the help!

[HondaMan]

If it were me...I'd at least attempt a JB Weld fixup of it, first? Clean it well (I use BrakeKleen), let it dry, and pack it with the JB Weld, fresh tubes. If it doesn't work, you can always tear it down and get it welded and repair the gasket surface another time.?

I have seen the CB750 with severe chain damage, in the form of gaping hole in front of the sprocket, run for decades with the JB Weld. Of course, problems show up when the cases have to be split one day.

[bwaller]

Not saying there is not a crack, but there is always a heavy casting line in that spot. Be sure it's not leaking from elsewhere by pulling the pan & get a look for it from the inside. I have used JB Weld inside the case, so if there is a crack you might slightly gouge it with a dremel inside & out and try JB. Clean well.

[DaveBarbier]

I would clean it really well and make sure there's a crack. I know you said it IS a crack, but the 550 has this crack looking ramp thing in the case. All 550's do that I've seen in person and online. Could be leaking from above and collecting in that.

[strynboen]

think it are a castting you see..normaly they dont crack there..just use some brake cleaner..and look for oil leaking...if no leaking..there are no crack..

[Ace Blackwell]

d_benet, I have a 77 CB550F.  It has the same mark on the driver side rear of the engine.  I've never had an oil leak, even since it's be just sitting.   It' must be a manufacturing or tooling mark of some kind.   I'm hoping lol.

Ace

[CycleRanger]

It's just a mold/casting mark. My '77 550 engine has the same feature in the same location.