Has anybody done a custom exhaust on their bike.

 

I repacked the Muzzy at 10,000 miles.....does that count? LOL

 

A few guys around here have drilled out the stock muffer and welded on bigger outlets..........

 

Any custom mufflers.

 

Yes. A highly skillfull TIG welding friend and I did one for my SR500 about 20 years back, using some mandrel bent tubing I got from, of all places, J.C. Whitney's auto catalog for under $30 and had enough bends left to do another.



The stuff we used was bare steel, this is aluminized, I'm thinking it might be better to try to get bare steel if it is to be chromed. I'm thinking Jet Hot will work over this stuff.

Here's my pipe on my bike.



same pipe just change up in bike



Since it isn't like a show bike or anything, we didn't grind any welds and I didn't get too shook up about the pipe turning blue.

I got two 3" radius bends, which are full 180 degree bends with about 10" or so of straight pipe on each end, and a 45 degree bend (which wasn't mandrel bend, only flaw). We cut up the bare steel pipes and tacked up the parts as we went, then he welded them up complete. The guy is an artist with a TIG.

We only had one error... I forgot to put in an exhaust gasket and it goofed up the pipe fit. I had to grind off a bunch of metal at the head pipe to make it work. If you do an exhaust DON'T FORGET THE EXHAUST GASKETS to get a proper fit.

I orginally wanted it nickle plated for more dirt track look, but it got chromed by error. Now if I did it again I'd send it to Jet Hot for their ceramic coating. Never turns color and is virtually maintenance free.

So, some exhaust bends and a TIG welder, a hack saw, and an eye for where it should go. As you see we took it up over the cases and behind the kick starter with the bend cuts. We didn't go behind the shock or anything because I was doing up an old look like the Norton Manx and Matchless G50 high pipe road ace set up. My brother rode it before I got what little heat shield it has on it - burnt a nice hole in his new black jeans.

I will eventually do something like this again on something I buy. It wasn't that hard, about 3-4 hours on a Saturday.

 

Yeah! Thats cool I want to do something like that for my klx 250.

 

Two important things:

First find out what is a good straight thru diameter for the header since you likely don't have the technology to do any sort of "power bomb" thing or expanding head pipe set up. Somewhere there will be some information available on the good head pipe ID and that is the pipe you need to get. The SR500 used 1-5/8" ID pipe (likely too large for a 250) so that is what I got. It was quite well established that size was right, based on information from racing and the great late Gordon Jennings in his articles on SR500 hop up back in 1978.

Second, find out the correct length needed to the megaphone/muffler can. There will be a "best length" from the head to the end of the header pipe if you can find it or someone here has a good example (again, it would have to be a straight pipe, not one with an expanded middle) on their bike. My SR had the established length at 33" from the the head to the tip, again from racing experience (flat track pipes were almost exclusively 1-5/8 ID and 33" long) and Mr. Jennings' experience in 1978.

So you need to do some research. If you can't find numbers, I'm kind of betting if you could do some measurements on a KXF250 motocrosser you'd get real close into the ball park. Maybe someone here on the KXF or motocross group could get dimensions for you if you can't get them. The KXF pipe is clearly going to be close on pipe diameter and length with both being same displacement, plus I doubt the small variations would make or break your performance. You might even be able to source a KXF (or other) muffler from someone who did an aftermarket pipe on ebay. Essentially build a motocross spec pipe for your bike.

One other long shot would be to measure up one pipe on a 1000cc sportbike header from head to collector and use that length and diameter, but I'm not sure how the collector set up may affect length. I know from being in the shop and around some drag racers, that longer smaller head pipes tend to be used on smaller engines for better power, short big pipes on big blocks. For example look up small block Chevy headers and compare to big block Chevy headers. So biggest and shortest isn't best and there is some science and calculation involved.

Once you have the necessary knowledge, go buy the pipe that is closest to the diameter you need. If Whitney doesn't have it, do a search for "mandrel bent tubing" to find a source. By the way one of the listings in Whitney was for stainless, if you want to avoid coatings and corrosion for the most part.

 

A. Graham Bell has a couple books on exhaust tuning. Both 2 stroke and 4 stroke performance tuning. They are both good reads concerning this topic.

Nice work klx678 on the exhaust. I too have used JC Whitney exhaust components in the past. In the end, I found it easier to hit up my buddies muffler shop and slide him a few beers. lol

 

Wow... another A. Graham Bell writing a book on exhaust tuning! I mean that certainly isn't the phone guy for sure... right? Sounds really stupid on my part...


I will mention that Jennnings wrote the book Two Stroke Tuner's Guide if anyone ever needs to figure how to make an expansion chamber. Not too sure if he did anything on four strokes. I guarantee I will be looking for the Bell stuff for sure. If you know the title or a site where we can buy or read the stuff let us know. I've wondered about that. I've just never seen anything yet, but I haven't looked yet. With all the stuff already done by the flat trackers and Jennings for the SR I didn't have to find it.

 

Check out this one. Excellent job in my opinion.

https://www.kawasakiforums.com/forum...ad.php?t=33317