help please motorbike engine welding????

[garath pentland]

hi guys was looking advice on a 1998 yamaha thundercat the casing that holds the starter ring gear etc was broke during an accident but it has broken two parts of the actual engine block itself ive posted pics hope they show up ok, i was told if the block is magnesium it will have to be totally stripped, but what is the actual block made from i was hoping to have it done the way it was, it doesn't hold much oil or pressure so just need a edge to seal to.... any help would be great

 

[Fazerruss]

It will be aluminium. It could probably be done without stripping the engine as its just to build up a mounting flange rather the sealing up a crack in the case with oil seeping out contaminating the area. I've done a similar job in the past on a Honda with the MIG set up for ally (pure argon, Teflon liner, alu wire) but would be better to TIG.

Find someone with a TIG and get it built up with weld, grind back to shape with a die grinder/ dremmel then re drill and tap the hole.

 

[garath pentland]

thanks for the reply, was worried that it would be a disaster the worse one needs built up to be able to rethread the bolt back in again

 

[Pete.]

Actually the rear one with the broken thread is the easier repair. Simply weld the piece back on, fit the outer casing, fit a drill bushing of some kind, drill and tap for M6. Don't try to weld over a bolt to preserve the thread, you'll never get the bolt out.
The front one looks like a small lump is broken off but it's also cracked across the lower case bolt pillar and there looks to be a tiny crack in the rounded part of the casing in front of the bolt though that might be a scratch. You need to gouge and weld these or when the engine gets hot they will leak oil.

 

[garath pentland]

Hi Pete yes I noticed the cracks in bolt pilar when the pics on the laptop just right of that is scrapes with a screw driver just?, the other one I don't gave the piece so it will need built up to thanks!