Vintage Dirt Bike Q & A

Does anyone have experiance restoring exhaust pipes. I have an OEM pipes for a 74 CR 125 that are have small to moderate size "dings". I know of a few places that specialize in exhaust pipe restoration, however, they are somewhat expensive. Someone suggested filling with lead but I am pretty sure that it would melt and fall out. I thought of taking it to a welder and having the dents "filled" and then ground smooth? Any suggestions would be appreciated. Thanks.

You have a couple of options. You already mentioned one, having the pipe professionally repaired.
Pacific Crest Pipe Repair does good work for a fair price. The only filler I know that will stand the
heat is hi-temp Lab Metal but it is difficult to use and hard to get good results. Permatex makes
a couple of products designed to patch and repair automotive exhaust that should work though
I haven't tried any yet. Another possibility is to use a stud gun and a slide hammer to pull the
dents. I did this on one of my pipes along with some heat from a torch and it worked great on
the smaller (not creased) kind of dents.

I do know that if you try to fill weld what is basically heavy gauge sheet metal, you should be
extra vigilant controlling heat build around the site because it would be very easy to burn a hole
in the pipe making the dent problem look trivial in comparison. If you decide to pursue that route,
it would probably be a good idea to have a professional do the work.

Good luck with it.

dogger

_________________
1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

Heres how we used to do it at the shop I worked at. First, if your not comfortable using a torch leave it to someone that is. Second make sure the pipe is as clean as possible inside, throw some small nuts and bolts inside, shake to remove as much carbon as possible. Your gonna need 2 freeze plugs, a welding torch a bike pump and some safety wire. Find 2 rubber type freeze plugs that are the right size. In one replace the bolt with a long shrader type valve stem. (Double nut it so you can tighten it to expand it without stripping the fine threads on the shrader stem.) In the end of the pipe, safety wire the plugs to the spring mounts on the pipe. If you don't-guranteed those things will pop out when you start heating the pipe. Now using a bicycle pump put about 2-3 lbs of air into the pipe and with the torch,start heating the dent up using circular motions slightly bigger than the dent. Once the metal starts getting rosey red hot the dent should start coming out due to the expanding air inside and the metal getting weaker in its heated state. For exteme dents or ones with a sharp edge on them it took two of us, one to pump a couple of pounds of air into while the other kept the dent hot. After big dents,let the air out of the pipe and let it cool down to room temp. Don't cool it with water.Don't put too much air in the pipe no more than 5 lbs or It could explode or the pipe can split.Be careful, use caution.

Thanks for the inormation. I have heard good things about Pacific Crest Pipe Repair. I have 4 pipes needing repair. Three have very minor dings and the fourth has a few bigger dents. I may try it on my own on one and see how it goes. Dogger, did you use Pacific Crest Pipe Repair for your CR 250 shown in this forum? Either way the pipe, as well as the entire bike, look great. Thanks again.

Thanks for the kudos PACDESIGN. Yes the pipe was done by Pacific Crest.

The pipe was so badly damaged (really mangled on the bottom), that
I ended up taking some pics and emailing them to Pacific Crest to see if
it was even salvagable, I had my doubts. They said they could do it and
they did a fine job with a 24hr turn around. The pipe still had a couple of
small dents when I got it back as seen in my "finished" pics. I got rid of
those using a stud gun and slide hammer like I mentioned in my post. The
pipe looks and performs like new now. I've enclosed a "before" picture of
my '73. Unfortunately, it's hard to see how bad the pipe was on the bottom,
but you can see all the dents on the side.

I believe Pacific Crest uses the technique Oldpromxr described in his post
which I think is good info and want to try myself on my '79 pipe.

the only restriction I'm aware of with Pacific Crest is the pipe has to have
a removable vs integral silencer.

Keep us posted on your progress and post some before and after pics if
you can.

dogger

[img][/img]

_________________
1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

Hey Dogger,
thanks for the photo. It gives me hope. I had seen your after pics, but not a before. What a difference. In the photo the pipe dosen't look that bad. I will take your word for it that there are dents not visable. I think I will do what you did and send them a picture to see if the bad one is salvageable. The others I will try the stud gun idea. Thanks again.