Topic: Dent on frame rail

[Garage_guy_chris]

heat and air pressure inside?  water inside and freezing? those are my two contributions

[mpacey]

I just bought a 72 cb500 with the same issue. It never occurred to me that it was because of the crash bar I threw away on my way home from buying the bike.
So what was the final verdict and solution? How did the fix work out for you?

[Vinhead1957]

The easiest solution is to strip and grind the paint in that area and use body filler and primer repaint.

[750K]

If its just dented from the crash bar and not a bent frame from something else I'd use fiberglass strand body filler, it will flex if it has to and not crack unlike the plastic filler. Fill sand and paint, forget about it.

[mpacey]

Plastic filler sounds like a plan.
I was looking forward to my build, and was bummed about scrapping the frame and having to part it out. Winter project is back on!!

[Don R]

JB weld would be my option. Relax and enjoy your build. Some of the suggestions although well intended are a bit extreme.

[lucky]

If you heat the center of the depression with a torch to dull red it initially expands. May pop out wards.
After it cools it will shrink just slightly. It should look slightly better.

Do not put water on it. Just let it cool at room temp.


If you drill a hole in it and use a dent puller it could look worse because the tent puller will make a protruding volcano shape. I would not do that.


If you weld the hole that the dent puller requires that will cause shrinkage as it cools. It will just look worse.

I think I would go with the Bondo myself. It will look perfect.


You have never pulled a dent I see.  Yes the hole will pull high like a volcano but you hammer and grind it back down and then fill the hole.  You can fill with lead (old school) fill with brass(braze) or weld with steel.   Bondo on a frame for only cosmetic dings only.  Frames flex and the inconstant densities. Bondo (soft) steel (hard) will crack at edges.

The frame is much thicker than sheet metal of a car.
The frame is .062 thousandths thickness.

[BeSeeingYou]

I just bought a 72 cb500 with the same issue. It never occurred to me that it was because of the crash bar I threw away on my way home from buying the bike.
So what was the final verdict and solution? How did the fix work out for you?

Just use JB Weld like DonR and powderman recommended.  You can buy it for a few bucks in the small quantity you need.  I think it's better than "Bondo" type fillers for small areas like this.  Dries fairly quickly, is hard but sands easy and feathers out nice.  It's a modified epoxy so it really holds on.   I used it to smooth out all the ugly welds on an XS650 frame....didn't have any dents but the XS has (had) some pretty ugly welds on this part of the frame.  I don't understand why it needs to be complicated by welding, brazing, grinding, drilling, pounding......  keep it simple and easy.  I got it in a set of 1 oz tubes (resin and hardner) and it was enough for the whole frame.

[BeSeeingYou]

heat and air pressure inside?  water inside and freezing? those are my two contributions

  Don't even consider it.  Water expands 10% when it freezes...so how do you control it and make it apply pressure to the dent only.  Once in awhile you see these "techniques" mentioned for gas tank dents too...usually by people who have never tried it themselves.  Only trust the advice of those who have subjected themselves to their own advice. 

[commando1954]

Build up the dent with lead then file off.

[Lostboy Steve]

I usually build up the area with some weld and then grind, file and sand.

[Retro Rocket]

my way: drill a hole opposite side of the tube, hammer the dent, weld the hole.

mec

This is the way i would do it....