Topic: 1975 CB400F Crankcase cracks below oil filter

[Cablecarusa]

I was cleaning up the engine (out of bike) and found three small cracks on the crankcase just below the oil filter housing. The motor has about 9k and looks to be very clean (sat in garage since 81). I don't want to take the motor apart if I don't have to. Suggestions??

[Powderman]

Are they actual cracks or those crack looking spider webbing in the casting?

[Cablecarusa]

They are actual cracks with a length of 1/4 to 1/2 inch. Wierd because I didn't see any oil leaking from them

[Don R]

Probably a cold spot in the casting, if there's no leak I'd go forward.

[MoMo]

can you  post a couple good close up photos ?

[Cablecarusa]

Thanks all for the response, I'll post a couple pics in a few.

[Cablecarusa]

Here's one

[Cablecarusa]

And no.2

[MoMo]

Thanks, I've never seen anything like that but it does seem to be superficial.  Could have happened from someone beating on the oil filter retaining bolt.  I'd clean the area, use something like JB Weld, button it up and keep an eye on it....Larry

[Cablecarusa]

Many Thanks! I'll get some JB tonight

[Don R]

 I JB'd some cracks in a set of chevy 292 turbo heads. The same heads Earnhardt hated. They lasted until race season was over. You're ahead if they aren't leaking, could have been collision damage to a previous filter and bolt.

[Flyin900]

I would suggest using the JB High Temp metal epoxy on that fix not just straight JB Weld. it comes in a grey stick that you knead a small amount as required together and then apply to the cleaned area.
I have used it numerous times on bike engines and it is rated to 450F continuous and can be sanded/painted if necessary.
I rebuilt missing/broken fins on a CB 350F head over a wire scaffold covered with this material and was able to sand and paint them like it never happened.

Never had any issues with heat or bonding or the repair holding the high temp paint.