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91 kdx pipe mod

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Posted by: ZKDX---------------------

has anyone done the pipe mod as directed by canadian dave, do you have any tips, hints, pictures, etc..before I attempt this.

Thanks


Posted by: 19Brendan81---------------------

I have done it...and it was a piece of cake, well I cant take all the credit...my mates dad is THE MAN with an oxy and he welded it back up for me. Basically cut as per the directions on Daves’ site (I used a grinder not a hacksaw blade though) and then hook into the packing. It took about 5 or 10 mins to cut the pipe, and then about 20 mins or half an hour to remove all the stuff. I used the grinder in here too on a couple of stubborn spot welds. Other than that just use a good set of pliers and a screw driver and it will all come out. I didn’t have Vise-Grips to use but if I did I would have, they would have made things a bit easier. After that was all done I took it to the local engine rebuilders and got them to pickle both bits of the pipe for me so that all carbon from within was dissolved out. It looked like a million bucks after that treatment! Now just weld it and paint it and you’ll be laughing. Without a shadow of a doubt the power difference was noticeable and substantial, and finally my bike sounds like a two stroke! Do it man, and let me know how you go.

P.S Unless you know a good welder, don’t use a grinder to cut the pipe as it makes quite a large gap.


Posted by: jerryme72---------------------

does this pipe mod go for the stock pipe a 91 kdx 250 also?thanx


Posted by: twocycle---------------------

I did the pipe modify to my 89. It really does wake up the bike.
Make sure you mark the pipe as in Canadian Dave's instructions. The hard/dirty part is getting the old mesh out.
I also took the opportunity to clean out the carbon and fix some dents. I used a mig welder to weld it back together.


Posted by: ZKDX---------------------

Pipe mod completed. will get some pictures posted for future reference to anyone. Wasn't real tough. Tig welded up my holes where I drilled out the spot welds, then mig welded the rest. Clean out carbon while I was in there. Can't wait to see the difference, now just waiting on my susp. to be completed by my buddy in AL!


Posted by: Engloid---------------------

Quote:
Originally Posted by ZKDX
has anyone done the pipe mod as directed by canadian dave, do you have any tips, hints, pictures, etc..before I attempt this.

Thanks


If you're talking about splitting the expansion chamber and gutting it, don't bother. I did it to mine, and felt it was wasted time. Gutting the stock muffler made more difference, but did make it louder. I then got an FMF and put it on. I kept the power I gained from the gutted one, but made it a bit quieter again.


Posted by: 19Brendan81---------------------

I completely disagree with Engloid, as do many other people who have done the mod. Im interested to see what you think when you get on your bike ZKDX. As for Jeremy72's post about it working on the KDX250, I am not sure...have never heard of anyone doing it.


Posted by: jerryme72---------------------

For anybody interested with a 91 kdx 250,,,,I took off my stock pipe and dropped a small stone into it and it came out the other side-no problem-so than i took a piece of stiff wire and that went through pretty easy also-so just to be totally positive the stock pipe didnt have a mesh wall inside,the pipe is really really heavy,i drilled a small hole so i could see inside the pipe-the only thing i found is that the stock pipe is doubled walled with steel and between the steel is a layer of fiberglass packing probably to reduce noise-I brazed the hole shut,grinded and painted-next step is a fatty pipe just to shed some pounds.......jerryme


Posted by: rlbranson---------------------

I cut a window about 5" by 5" right by the indentation for the radiator hose on the stock pipe for my 1998 kdx200. Actually the cut out peice includes the indentation. After removing the extra sheet metal and oil soaked fiberglass I welded it back together painted it and put it back on. It made a noticably more power on my bike. I don't know what it does on a 220.

Bob
kdx200


Posted by: 80elkster---------------------

I did the pipe modification to my 93 KDX200 with a very notable power increase I also had to change the jetting a little leaner than stock. I also put in a set of dual stage reeds. Man the difference is awesome. You can just lug the hell out of it on the trails and it still pulls hard just off idle, almost like a big thumper (used to have a XR500). I can ride one gear higher over the same trails I've ridden before.
I do have to say that getting the mesh out was a PITA, and very messy. I have read elsewhere in the forums that someone heated up their pipe in a camp fire and all the oils in the mesh and fiberglass turned to ash and came right out.
But hey the increase in useable power was worth it IMHO.

If you just do the mod and don't follow through with a jetting change you probably won't notice a big difference.

Try It you'll like it


Posted by: lepper---------------------

When I had my 92, I put a PC pipe on and sold my stocker to a guy who modified it. He spent some time on it and was a professional welder. He was not impressed with what he got out of the pipe and said he would not do it again but rather just buy an aftermarket pipe.

Your results may vary though....


Posted by: Canadian Dave---------------------

Engloid if you gutted a 89-94 KDX200 pipe and didn't see a meaningful difference then you have another issues with your bike i.e. jetting or ? Gutting the pipe makes a VERY noticeable difference.

jerryme72 I think there is some confusion as to what is being removed from the pipe. The " Screen" is perforated metal, much like you'd see used in most silencers, that sandwiches a layer of fiberglass between it and the inner wall of the pipe making what is normally referred to as a double wall pipe. I would not prevent a rock from being passed through the pipe. I can't answer your question as to whether the KDX250 came with a double walled pipe without drilling an exploratory hole in one to find out.

David



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