TOPIC:

The GPz I got this Sunday has an old and pretty ratty set of kerker head pipes. The are nice in that the clear the oild filter without being too low. They are not nice in that they are dented up a bit at the lower bend jyst before the collector.

How would one repair this, or where might one take it for repair. Typical cost?

Thanks.

-Duck

If, by repair, you mean can the dents in the head pipe be removed... I doubt it. They can be filled in and painted or something but pulling dents in an exhaust tube wouldn't be very easy. Most KZs/Zs etc have dents in that area... clean the pipes and paint and no one will notice till you get enough money for a new exhaust system.

To get the dents out, drill a hole in the pipe on the opposide side of the dent, then use a small rod of some sort to pop the dent back out (hitting the rod with a small hammer). (You may have to heat the pipe a bit.) When finished weld the drill hole, and grind flat.

77KZ650 - Have you tried this yourself personally? The method you refer to might work for sheet metal but I would be curious as to how well it works with multiwall exhaust tubing. I wonder how you will pull the dent out... just stick something in the hole and pull? Just curious...

George-

Head pipes are multiwall? These kerker look like single wall. Guess I could drill a hole and see. Easy enough to plug afterwards.Dents are in and aroud bend that is just in front of the collector. Problem with having bike and workshop 42 miles from my house is I can't just go out and look at it when a question occurs. Upside is renting from a friendly machine shop and low rent

BTW, if anyone needs any work done that requires a 3-axis CNC mill with 24x48 inch table, my workshop landlord is an experienced aerospace machinist and will quote from autocad and hand drawings or a faxed sketch. Remember, tighter tolerance and finer finish both = more $ so don't put in any tighter tolerances than you need.

This email address is being protected from spambots. You need JavaScript enabled to view it. is his email
770-704-7558 is phone and fax.
It's a small shop.
John Lorber.
He rides a CB750 Custom.

IIRC, setup and machine time is about $50/hour.

-Duck

I use a resistance type welder to tack brass studs onto the pipe, then a special type of slide hammer that locks onto the studs with a knurled cam.
I can really get metal straight, to the point where no filler is required, but that type of situation is reserved for powdercoating and chrome canidates and exhaust as you mention, since it is fairly expensive to do. plus, to get it metalfinished, so that no fillers are used, the headerpipe would have to be removed from the bike, so that you have access to the inside. typical dents like that @$38 per hour usually run just under $100, but when it's done, it's straight. I used to do this all the time with a regular stick welder on dirtbike exhaust. always used to crush up the pipes on my old 1978 RM125.

If you take it to a bodyshop, I am sure they'd be able to do what I just mentioned.

Thanks.
I hadn't thought of applying slide hammer to pipes.
-Bob

The dent can be neatly cut out and a section of exhaust tubing cut to match, welded in, and ground smooth.

Small dents,don't worry about it!
Medium dents,I go with a slide hammmer,but some other good ideas here.
Crushed,I have found some good automotive exhaust guys can handle cutting out a section and replacing it,as long as they can get aroud the pipe with the mig welder.

You might check with these guys...I have heard nothing but good things about them, but I'm not sure if they do street exhaust.

www.piperepair.com/

George, on single wall pipes, the drill hole is on the opposite side of the pipe that the dent is on, then you tap (from the inside of the pipe) on the dent to force it to come back out. Haven't done it personally, but I heard the trick at my local drag strip.

If you drill a hole opposite of the dent it will be on the inside of a radius. How does the slide hammer work where it can punch the dent outward? (I have never seen a slide hammer in person). How would it be different than drilling a hole and putting a punch in the hole to beat the dent out with a regular hammer?