Scooterotica

I'm just in the process of replacing my gearbox and on reassembly one of the 7mm studs has pulled out of the casing. Most of the studs have a small crack in the casing and the dowel holes are a slack fit, too. I can get the cracks welded no problem.

Am I right in thinking that you can up-size the studs/holes to 8mm for a stronger job and has anybody done this conversion? Any pics would be good, too.

Cheers,

Nick

PSC GP200 wrote:I'm just in the process of replacing my gearbox and on reassembly one of the 7mm studs has pulled out of the casing. Most of the studs have a small crack in the casing and the dowel holes are a slack fit, too. I can get the cracks welded no problem.

Am I right in thinking that you can up-size the studs/holes to 8mm for a stronger job and has anybody done this conversion? Any pics would be good, too.

Cheers,

Nick

You can,but as you say the casing is cracked on most of the stud holes,it may be better to have them all welded and then re-drilled and tapped to the correct size.

There are repair options like that but I'd say there's two reasons not to do it that way.

1. If you make the holes bigger there is less support for the stud.
2. The pitch of the thread is 1mm for M7 and 1.25 for M8 so for the same depth of hole you actually have more threads in the hole with M7.

If you have access to getting it welded get it done properly as Hxpaul says


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Get them welded, don't risk it getting worse. Go to someone who knows what there are doing, too. I had mine done at MB and it was perfect.

Check out my post from 5 days ago..... Why not helicoil? If the holes after being drilled out can take a fully formed thread with a helicoil tap for an insert then I don't see a problem. Couple of good ideas for replacing dowels on the other thread as well.