Frame rusting through

[Czekus21]

Has anyone had a problem with their frames rusting through from the inside? Mainly the left tube under the motor. I found a spot that rusted through from the inside and found that the frame was rusted very thin. Almost scary thin. I repaired it and it will last probably a few years but that tube will need to be cut off and replaced.
This is not a rant and rage post. Just an FYI. If your bike sits outside alot, You may want to check your frame. Mabee with a sharp tip awl or some kind of poker. The repair started as a rusted through crack. When I opened it up to get to solid metal, It went to a dime size hole. While filling the hole with a plug and a welder, The repair went to aprox 6 inches long and the width of the tube.

[Dragonrider]

That's just plain scary!

I would guess water is getting in your frame from another cracked weld or something higher too...hence the rust from the inside...

[TopCatGr58]

Hey Czekus,

You're in luck, I know a guy in Zap, N.Dakota that will eventually have a spare 80-81 MNS FRAME that he'll want to get rid of, ONCE he strips it of most of it's parts to send to me for my basket Case!! He's TrukLeon, PM him, or he may see this and contact you directly!? Hope he doesn't mind me offering it for him!

[Ken Talbot]

The frame on my restoration project also has a few nasty little holes on the left tube under the motor. Two holes are visible from the outside:


One hole is visible from the inside:


My plan is to 'double wall' the bottom half of both of the frame tubes. The tricky part will probably be getting the half-round shell to curve around to at least where the motor mount is. Any welders in the crew got any better ideas?

[Czekus21]

Here's a suggestion. This is what I'm going to do when I eventually restore MIYAMI. Cut the tubes off of the bottom of the frame and fab some new tubes out of thicker steel. I'll be useing the same outside diameter ( 7/8"), but the thickness will be instead of 1/16", up to 1/8" or 3/16" thick. I feel it will give more strength without much more weight while maintaining the original tube size. The majority of the weight/load on the frame is born by the upper tube, ( under the tank ) The down tubes mainly hold the weight of the engine/trans and gives a little bit of stability and body to the bike. If the upper tube has got rust, I wouldn't suggest riding it AT ALL until it was fixed.

[newmaac]

I have no idea what the cost would be to ship, but I have a good frame that you can have.
Actually, I could just take a sawzall and hack off the part that you need to replace, then you would not have to re-register the bike with a new frame.
Let me know if you want to get into it that far.
I am on the left coast.

[trukleon]

chopping

I have to agree with the hack part as legaly one must reregistar,,,especially in so dak.,,,, unsure about canada.. My question is with heavier pipe you're changing weakpoints even if you were to use a low heat tig welder,,which would also go hand in hand with heavier walled pipe or am I way off base here .. Anything is better than half which is what the frames are reduced to even though the integrity is more than likely less than that.. The old saying comes to mind your chain is as strong as your weakest link

[trukleon]

Frame

Got misdirected there,,,, will cut frame or send whole,,but what about those gold colored wheels???

[Ken Talbot]

I've actually got a spare frame in my back yard that I could hack pieces from. It just seems to me that I'd get a stronger result by adding another thickness to what is left...

[Renegade]

If the concern is the strength at the weld when you replace the bad sections, do it like the Harley guys do when they modify frames.

1) Make up a piece of steel the same OD as the tubing, about 3 inches long.

2) Turn down the OD of each end (about 1.25 inches long) so that it just slips into the tubing.

3) Insert this plug between the ends of the tubing to be repaired. Use a come-along or similar to ensure that the frame/plug joint is fully seated.

4) Drill a small hole through the frame tube (about 1/2 inch from the end of the tube) and spot weld the tube and plug through this hole. This will keep the joint from trying to spread apart as you seam weld the ends of the tubing to the plug.

5) Grind your repair smooth, paint it. and reassemble the bike. The repair will be invisible, and stronger than the original frame.

[Mike F]

Hi All
I've seen a few frames with the rust holes. I think t hat may be we have more rain here in England. What seems to happen is that when the bike is out in the rain and on its sidestand, the rain gets inside the frame around the headstock (the welds aren't great around here) and collects in the left hand frame tube where it's lower. Another place that it can get in is around the big bolt holes for the oil cooler.
Keep revving
Mike F