Tools For Pipe Dent Removal?

Joined
Feb 5, 2005
Messages
129
Likes
0
#1
I got a "not too bad" dent in my FMF Fatty (1994 CR265) pipe earlier this spring. I had the pipe off to have a look at the piston and cylinder recently. I thought about getting it removed, however am too stubborn (spelled c h e a p) to have a shop do any work for me. What tools can be used to pressurize the pipe, and heat it up to remove the dent? I have a compressor, is there are plug I can get with an air valve in it?
Will a propane torch get the pipe hot enough to remove the dent? How much air pressure should I put in the pipe? One last question, I don't want to ruin the nice chrome finish, if there is any blue-ing is it easliy buffed out?
Thanks in advance.
Keith
 
Joined
Jun 16, 2005
Messages
156
Likes
0
#2
Cant help you out on your question, but how do you like the big bore kit for that CR250? I have a 97 CR250 and was wondering if it's worth it. What kind of gains are there, bottom, top or all the way around better.
 

bclapham

Lifetime Sponsor
Joined
Nov 5, 2001
Messages
4,340
Likes
0
#3
there was a guy selling the tools on E-bay. i think you need to seal it, pressurise and then heat the dented area- but all that compressed air, combustible gunge, and heat sounds scary to me.
 
Joined
Feb 5, 2005
Messages
129
Likes
0
#4
I bought my CR already bored out to 265cc. I did not know this until I went to rebuild the top end and found a weird sized piston in there. I am not sure how the bike ran as a stock 250 so it's hard to really be accurate in comparing. I do know from riding a friends CR250 stock, 2001,that there was quite a difference in power. The stock bike didn't seem to be as wild, even with an 11oz flywheel on mine weight it is amazing. There is plenty of bottom end, I ride only tight woods, single track and love it. I would say definately more bottom end than stock. My bike also had the FMF Fatty pipe as compared to the CR250 that I rode which was stock. When I think about 15cc difference over stock, it really doesn't seem like much in theory, but wow, I know I can feel it. The previous ower was too unaware of the 265cc kit in the bike. He went on to say whenever he went riding with his buddy who had a 2003 CR250, they usually switched bikes as his buddy loved how wild the 265cc bike was. Neither of them knew why there was such a difference. ;)

To answer your question, all around better gains in my opinion. I don't ride on a track ever. For woods riding I love it.
Top end? Can't really say if it's better or worse as I spend 80% of my time at mid to low power band. Oh, did I forget to mention wheelies? Man, its so light on the front end I can't believe how easy it is to wheelie. :laugh:

To sum all this up....I love my 1994 CR265. I will be riding this bike for a long time yet. However reading about CR500's on here lately has peaked my interest. :nod:
 
Joined
Jan 7, 2001
Messages
320
Likes
0
#5
I made a set of of 2" and 3 inch pipe. Simple really, just drill 3 evenly spaced holes and weld 3 nuts for screws to go thru the holes on a 1" long ring cut from the pipe. Then weld 3 long nuts (for joining threaded rod I believe) that go along the length of the pipe also evenly spaced but in between the first 3 nuts. Now all you need is a plate with 3 holes drilled in it for bolts to go thru it and into the second set of nut on the ring. The bolts go thru the ring and tighten just below the weld on the pipe header. Then tighten the plate down to the flange with a piece of rubber between the plate and the header to act as a seal. Make one setup for each end.

pressure should be about 20lb but do not use compressed air, rather use nitrogen to help avoid an EXPLOSION. don't forget that the pressure in the pipe will rise dramatically (the ideal gas law states that P1*V1 = P2*V2 since V1 = V2 the pressure is directly related to the temperature of the gas inside the pipe. You should also put a blowoff valve in the small end plate. I've seen a pipe explode using this method and it sounded like a quarter stick of dynomite going off. fortunately the pipe just ripped wide open and nothing came off. If it did it would surely remove whatever part of your body it hit!

I don't think a propane torch is hot enough and an acetylene torch usually will burn off the plating.
 
Joined
Jun 7, 2005
Messages
58
Likes
0
#6
If you have a big enough freezer, fill it with water, be sure to cap both ends so they won't blow off when the water expands, and throw it in the freezer overnight. I have heard of it being done and working well, the only thing is you might need to empty out the freezer, or if you have one of those big chest freezers. It's a safer bet than heating up and trying to pop out the dent, possibly ruining the integrity of the pipe.
 
Joined
Feb 5, 2005
Messages
129
Likes
0
#7
Holy cow! That freezer idea is a darn good idea. Just might work too. I'll have to try it. Thanks for all your input. The compressed air sounds dangerous. Yikes!
 
Joined
Dec 6, 2002
Messages
105
Likes
0
#8
Just remember to tell the water to focus on the dent, otherwise the seem can open....Not recommended.

Plug the ends, compress the pipe at 3bar & heat the dent in circle moves. Make sure to let air out as the pipe heats up.
Safety goggles.

There used to be pictures on the JustKDX forum on the brackets use to plug the ends. i Copied that & it works well.
 
Joined
Jul 17, 2005
Messages
184
Likes
0
#9
Yeah, propane is not hot enough. It takes an acetylene torch. And, yes, it will discolor the chrome finish.
 
Last edited:

holeshot

Crazy Russian
Joined
Jan 25, 2000
Messages
1,823
Likes
0
#10
keithb7 said:
Holy cow! That freezer idea is a darn good idea. Just might work too. I'll have to try it. Thanks for all your input. The compressed air sounds dangerous. Yikes!

I tried the freezer thing on a stock CR500 pipe. If you check the freezer every 15 minutes or so, it might work (but maybe not). Mine was a failed attempt because the pipe split at the seams (but the dent was gone ;) ). Pro Circuit got my business as a result of that experiment.

It may work better on aftermarket pipes because they usually have a thinner wall and the weld seam is flat, not folded. Try it and let us know. :laugh:

For subsequent dented pipes, I found a local guy (near S.F.) that did a great job of removing dents for a reasonable cost. There was very little discoloration to the chrome.
 
Last edited:
Joined
Jan 15, 2004
Messages
88
Likes
0
#11
I fix mine all the time. As a precaution I stick the lighted end of the propane torch down inside the pipe to burn of any gases, but never get any reaction. Then I fit a big hunk of rubber I got from somewhere yonks ago and shaped into a bung into the large end with a big bolt and nut through it. I tighten the nut.
For the small end I use an old peice of inner tube, with a washer under the valve, and on top as well to prevent the rubber blowing out. I clamp this to the pipe with a couple of clamps, one a hose clamp and one an old radiator clamp. The radiator clamp bites into the folds of rubber better to prevent air leaks.
Then I super tape around the valve and washers and clamps so that the inner tube will not explode anywhere and tape it all down to the pipe.
Using only 20psi, which will increase to about 40 psi when heated I use two propane torches to heat the dent to a cherry red. I have one large heating torch and a finer brazing torch to more concentrate the heat.
Wear safety goggles, point the bunged ends somewhere safe and have a bucket of water with a wet towel nearby to throw over the treated area as soon as it is repaired to set the metal.
Its a bit nerve racking at times, but I have never had a problem doing this, and I've done major dents. I usually leave the smaller ones until I have a larger dent to repair, then do all at the same time.
Polish the area with scotch brite to get a bit of the shine back.
All this will cost is some propane refills once your set up, and I've fixed my pipe about ten times.
 
Joined
Mar 6, 2005
Messages
153
Likes
0
#12
I did this last night, using a compressor and an oxy. I used 4 layers of cloth tape over the inlet to the pipe (where it bolts to the motor) and a hose clamp. At the outlet end of the pipe, I used a push bike inner tube valve with about two inches of rubber left attached around the base. This was also clamped on with a hose clamp. The pipe we were doing had about half a dozen tiny holes in it, so it wasnt airtight. Which was kind of handy in a way as it prevented over pressurisation. We got the first dent out with about 10psi, the second much larger dent took 30psi and a lot more work. We then moved on to some dents in the header section of the pipe, about 8 inches from the cloth tape and hose clamp....we got one out with about 25PSI, then moved to the second and it was being stubborn. We hit 35PSI before the bung blew out. (the tape wasnt breeched, it just slid off the end).

We packed up after that.

I will definately do this again, but would be hesitant to do it in the header sections of the pipe where the metal is much thicker, and the heat much closer to the seal we made.
 
Joined
Sep 12, 2007
Messages
230
Likes
0
#14
i have a few dents in a pro circuit pipe i am going to try the heat method first but if it gets too dangerous looking i will try the freezer idea (good thinking on that one) ill let you guys know how it goes.
anyone else ever tried it??
 
Joined
Apr 18, 2006
Messages
1,534
Likes
8
#15
I have been waiting for someone to chime in that has actually tried the ice method. I was expecting that there would be major problems limiting the expansion to just the dent.

With the compressed air approach you can apply a controlled amount of pressure and heat up the spot where you want it to bend. I can see how that can be controlled. I can see it going wrong, but only in the area of the dent.

I have have my water pipes freeze and know that it doesn't limit itself to just one spot.

Rod