Dirt Bike Chassis Rust Repair

[Jigantor]

Today I started restoring an old Yamaha YZ 125.
The bike was ridden near the saltwater I think from the rust in the sub-frame.
Sanded off the paint, filed, chipped and generally removed rust scale to reveal the extent of the problem.
Two holes joined by a small bridge.

Ji

[Jigantor]

I ran a bead to try and find some solid steel around the holes.
When I saw sparkles shooting out of the pool I changed direction away from the hole until I had a bead all around both holes.
Then it was just a matter of a spiral bead pattern until the holes were closed.

Ji

[Jigantor]

The proof is in the tasting they say.
Ground/sanded the beads down to see if there were any inperfections.
Yes there are a few that need another TIG but not bad for a first run keeping in mind the size of the holes.

Ji

[LarryO]

Do you think it would have been better to replace the whole section?

[Jigantor]

Hi Larry,
Well the tube is CrMo and that is hard to find where I am.
The tube also has two bends which is another problem to get right without squashing it.
There are also two complicated brackets on it. These could be cut off and reused but I would have to make a jig to get them back on in the exact position.

This tube is part of the sub-frame and only holds up the seat.

Ji

[LarryO]

Cool dude. If its only a sub frame suport for a seat, no probs.

Was a little hard to tell without a bigger pic.

If you need small pieces of Cro-Mo, let us know and i might be able to help you out. Will send to you.

[Jigantor]

Hi Larry,
Thanks mate.
It is hard to get up here.
Bending tube is the trick, no one up here will do it.
They only have building product size dies like 76 diameter and up.

Ji

[Jigantor]

Yesterday I spent some time drilling out contaminants, welding and smoothing the rusted tube.
I also drilled some test holes in other parts of the tube to see if it was structurally sound.
Yep all good ready for paint.

Ji