I've snapped a bolt on the outer casing. Is it gonna be a problem?

 

Is it on top or bottom?

 

No it's one of the outer casing bolts. Will it effect the seal?

 

It might. Is it a top bolt or a bottom one?

 

Bottom one. Should I take the crankcase off and try remove what's left of the bolt or just leave it as is and hope for the best?

 

First I would see if its loose enough in the hole to try to back it out. If it's not, I would put some sealant on the area and see if it leaks. If the cover is already back on, just try it and hopefully it seals. You have nothing to lose at this point.

Broken bolt extraction can be easy or become a nightmare if you don't know what your doing.