Dented cradle tubes

lappedrider
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Tooele, UT US
11/11/2019 1:24pm Edited Date/Time 11/12/2019 5:02pm
Looking for thoughts on this as I see opinions all over the place on the web. Going to be restoring an 89 RM250. Frame is straight and solid, other than surface rust and this dent. My thought was just heat it and pull out with a weld on dent puller. Some say not to do that and I am not sure why. 🤷🏻‍♂️


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gristle568
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Newton, NC US
11/11/2019 1:36pm
I rebuilt a kx125 a few years back with a few dents in the frame rails, I just filled the dents in with weld and ground them smooth so you couldn't tell. Unless it bent the frame rail when it got hit, its just cosmetic.
3
kb228
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Mansfield, OH US
11/11/2019 6:13pm
Bending it back makes it worse. I like the above post. Weld and grind flat for cosmetic reasons.
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lappedrider
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Tooele, UT US
11/11/2019 7:50pm
kb228 wrote:
Bending it back makes it worse. I like the above post. Weld and grind flat for cosmetic reasons.
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m wrong but just wondering why.
kb228
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Mansfield, OH US
11/12/2019 4:54am
kb228 wrote:
Bending it back makes it worse. I like the above post. Weld and grind flat for cosmetic reasons.
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m...
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m wrong but just wondering why.
If you bend a piece of sheet metal at the crease it gets weaker with every bend until it breaks. Thats the simplest way i can explain it.

Filling with weld will recreate a round shape with more material and therefore be stronger than if you just pulled the dent.
1

The Shop

sandman768
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Saratoga Springs, NY US
11/12/2019 7:32am
If you are serious about riding the bike let me suggest this: strip to bare frame, sandblast & inspect frame for any cracks or stripped threads, now is the time to repair them. Then make a weld in skid plate, at that time you or your welder can fill the dent with weld & grind/ sand smooth. Fit lower engine cases back on frame to drill oil drain bolt access. Have frame refinished or powder coated. The RM”s of this era are notorious for poor handling chassis, the weld in skid plate will strengthen the frame and increase stability. This is a very easy mod.


harescrambled
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Warren, OH US
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11/12/2019 10:07am
kb228 wrote:
Bending it back makes it worse. I like the above post. Weld and grind flat for cosmetic reasons.
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m...
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m wrong but just wondering why.
you'd need to heat the metal to the point where you change the grain structure and make it brittle in that area. after that, it's more likely to crack where the heat was applied
lappedrider
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Location
Tooele, UT US
11/12/2019 12:38pm
sandman768 wrote:
If you are serious about riding the bike let me suggest this: strip to bare frame, sandblast & inspect frame for any cracks or stripped threads...
If you are serious about riding the bike let me suggest this: strip to bare frame, sandblast & inspect frame for any cracks or stripped threads, now is the time to repair them. Then make a weld in skid plate, at that time you or your welder can fill the dent with weld & grind/ sand smooth. Fit lower engine cases back on frame to drill oil drain bolt access. Have frame refinished or powder coated. The RM”s of this era are notorious for poor handling chassis, the weld in skid plate will strengthen the frame and increase stability. This is a very easy mod.


I do plan to ride it. This plan looks like the ticket.
lappedrider
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864
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Tooele, UT US
11/12/2019 12:38pm
kb228 wrote:
Bending it back makes it worse. I like the above post. Weld and grind flat for cosmetic reasons.
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m...
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m wrong but just wondering why.
you'd need to heat the metal to the point where you change the grain structure and make it brittle in that area. after that, it's more...
you'd need to heat the metal to the point where you change the grain structure and make it brittle in that area. after that, it's more likely to crack where the heat was applied
Makes sense. Thanks.
Tracktor
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The RTF/Amboy, WA US
11/12/2019 5:02pm
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m...
Thanks, but what about bending it back makes it worse? I would think regaining its circular shape while heated would be stronger than dented? Sure I’m wrong but just wondering why.
you'd need to heat the metal to the point where you change the grain structure and make it brittle in that area. after that, it's more...
you'd need to heat the metal to the point where you change the grain structure and make it brittle in that area. after that, it's more likely to crack where the heat was applied
Makes sense. Thanks.
I didn't do a full skidplate like above on my 96 CR125 build but I did cut tubing in half and form it to bottom of frame rails on each side to reinforce and cover the small dents. once welded & powdercoated it is barely noticeable.
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