How far can I drill into my broken case?

[Baroquenride]

Several months ago my chain snapped while riding down the highway. I know exactly why it snapped and it won't happen again, however it snapped off part of the case where the sprocket cover bolts to. I had a casesaver on there and it worked, but obviously broke the top mount in the process. I still have the mount and I JB welded it back on but recently it came off again because the screw is just going into the broken piece and not into the side of the case anymore. As you can see, the dimple is the end of the hole for the top mount and I'm proposing drilling into that dimple just a bit and getting a longer screw so that the screw has something to actually hold onto and keep the broken piece from falling off again. Anyone know if that would work or would that be a reeeeeeally bad idea?

Also, as you can see I'm pulling the spring out to roughly where the part that broke off held it. Does it matter if it's a bit more relaxed now or should I build that out somehow to put more tension back on the spring?

 

[Spice Weasel]

Youre asking for trouble drilling that, leave it alone.
The same happened to me.
Find a different way to bolt on a case saver, like by using the top roller mount, those cast mounts are too fragile for a case saver IMO.
I will simply risk running without one.
Ive left the spring where it is aswell.

 

[JonXX]

It looks like the casting boss there has lots of useable meat. If it were me, I'd check the parts manual and/or look for teardown pics of the inside of that case side and confirm that it's a solid casting boss, without an oil passage or dowel pin on the inside. Assuming it's solid, I'd drill it and helicoil it and roll on.

But that's me. If I bork it up I have a TIG welder I can fall back on.

 

[Baroquenride]

It looks like the casting boss there has lots of useable meat. If it were me, I'd check the parts manual and/or look for teardown pics of the inside of that case side and confirm that it's a solid casting boss, without an oil passage or dowel pin on the inside. Assuming it's solid, I'd drill it and helicoil it and roll on.

But that's me. If I bork it up I have a TIG welder I can fall back on.

So, because you have an SM610 AND a TIG welder I could use your professional opinion. Ideally, I'd like to weld that mount back on, but the welding shop here in Vancouver said that I'd basically have to bring in just the case due to the inside corners and the angles involved, plus he'd need to clean the surfaces really well to get a good stick, and lastly he didn't know what is behind that area and doesn't want to melt any rubber bits or warp bearings. What do you think about welding it back on? Think it's possible as it sits? At least better than JB Weld? I'd be willing to ride it down your direction if you needed to look at it in person.

 

[speedydave]

I think it could be welded if you pull the case apart. I had that done on an old dirt bike many years ago with a similar issue.

 

[Baroquenride]

Of course it can. I don't want to do that if I can avoid it.

 

[JonXX]

If it were me, I'd go the helicoil route first, because welding it (the right way) will take a lot more time. It *can* be welded on the bike, if you pull the sprocket and clutch arm off, but not nearly as well as apart and clamped down so it doesn't warp. If I absolutely had to weld it assembled on the bike, I'd only weld 1/4-1/2 inch at a time and let it cool, for the reasons your welder dude mentioned. It would be easier with an aluminum wire feeder, it could be spot-spot-spot welded more quickly. On the bike will definitely not be as good (strong and pretty) of a job as off.

Or you could also/instead of the above, clean up the mating surfaces operating room clean, and JB Weld them together, with a clamp that reaches across the cases to keep good pressure on it until it's cured.

 

[Baroquenride]

Not sure what you mean by Helicoil route. The threads are just fine on the part that broke off. If I can determine for certainty that drilling into the case will be ok, then I'll use the Helicoil in there to make it stronger. I'll probably just do the JB Weld route again but with the putty version, and use your idea or a variation of that.

 

[JonXX]

Not sure what you mean by Helicoil route.

If I can determine for certainty that drilling into the case will be ok, then I'll use the Helicoil in there to make it stronger.

^ That's what I mean by "going the Helicoil route."

 

[oldbikedude]

Not sure what you mean by Helicoil route

I think JonXX is talking about drilling & tapping whats left of the boss on the engine & installing a threaded insert. That boss could be tapped to size but they say the helicoil insert makes the threads stronger. If you grind the boss flat & use a helicoil you could make a spacer to extend it out to the case saver & not worry about the "webbed" part that would be missing. I would think if cleaned up real well with a nice tight fit...the broken piece could be welded back on well enough by a good welder without disassembling the bike. Maybe even drill through the broken piece & bolt it through to a helicoil as well as welding it for extra strength. Good luck with it.