125 style single bend pipe mod?

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BFD
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125 style single bend pipe mod?

Post by BFD »

So, some of you might think I'm crazy, but i want to find or make a 125 single bend/sweep pipe that will fit my 96 kdx200.

I did this on an 02 ktm 200exc a few years back. The pipe and silencer from a ktm 125sx bolts right up. With a little jetting enrichment, it took away some of the low end torque, but made it SCREAM up top!! Not to mention the added pipe clearance and weight savings.

I completely understand how the majority of woods riders prefer smooth linear low end grunt, but dont knock it itll ya try it.

Does any year of kx125 pipe have the same diameter exhaust port?

Has anyone been there & done that? If not, I'll let you know how it goes!
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Post by factoryX »

Why? The stock KDX weighs in at 240-250lbs, wrong bike to do this on.
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Post by kdxtreme »

They don't feel that heavy when your flogging it. :mrgreen:
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Post by SCREAM »

it'd be a sleeper thats for sure. everybody would think you were on a 125 until you ripped it.
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Post by factoryX »

lol. For what it cost you could just buy a 125 and sell the kdx. :roll:
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KarlP
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Post by KarlP »

Why not?
I don't know about the exhaust port diameter. You might be able to cross the 0-rings and see what that tells you.

You can always cut the cylinder engaging snout off the 125 pipe and weld on a KDX one. You might have to do that anyway to get the length right.

If it doesn't work out no big deal.
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Post by Julien D »

Not sure on the pipe diameter, but I can check a couple 125 pipes I ahve for you. I think it's a bad idea, but whatever floats your boat. :partyman:
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Post by BFD »

Well.... Thanks to everyone who voiced their opinions.

KarlP had a great idea, looks like a 94-98 KX125 shares the same diameter o-rings and rear rubber connector piece.

FactoryX, I don't understand how price and bike weight have any major efffect on why this would be a bad move. Keeping momentum and good line choice have more effect on trail effeciency. Cool animation by the way!

I'm bidding on a couple of non-plated pipes on e-bay, they're pretty cheap.$60-80

:supz:
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Post by SCREAM »

keep us updated, i'm very curious to see how this affects the bike, especially those with rb's mods.
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Post by factoryX »

In long run you have to look at how efficient your bike is. This basically covers gas mileage, power delivery, etc.. You're taking a bike with decent gas mileage, perfect power balance, and simply opening it up for more air flow for more peak horse power. This takes away the balance and all you would be getting in the end is a 250lb 200cc top end screamer that's useless for the woods for which it was designed to be ridden. But hey, I could be wrong go for it.
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Post by BFD »

Nope, you're right. It'd be like feeding crack to a billy goat. :lol: But how boring is efficiency? I haven't run into many NEW ideas for these green machines. The cool thing about this pipe idea(if it works) is that it would be a cheap easy, bolt on performance change. No boring, porting, or milling. 200 pipe for "slow" tecnical trails and 125 pipe for fast open flowing trails.
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Post by factoryX »

Buy a PC platium pipe for it, should boost the bike a bit for you. Simply replacing the stock exhaust takes off about a few pounds. Another thing to point out is the kdx200 h series already sort of runs mid-top(E series being the tractor bike), so it sort of already rides like a 125 if you want it to. I have a six inch scar on my leg from a pipe burn to prove it :mrgreen: Its actually the reason why I bought an 03 yz250.
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Post by Julien D »

>|<>QBB<
BFD wrote:Well.... Thanks to everyone who voiced their opinions.

KarlP had a great idea, looks like a 94-98 KX125 shares the same diameter o-rings and rear rubber connector piece.

FactoryX, I don't understand how price and bike weight have any major efffect on why this would be a bad move. Keeping momentum and good line choice have more effect on trail effeciency. Cool animation by the way!

I'm bidding on a couple of non-plated pipes on e-bay, they're pretty cheap.$60-80

:supz:
I happen to have an FMF pipe for a 1994 kx125 that's in pretty good shape. I don't have an H bike in the shed to fit it to, bit I think the E series outlet is about the same. If you're interested in the pipe, let me know. I can test fit it and snap a pic for ya.
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Post by Julien D »

looks like you'd need to re-bend the headpipe quite a bit to clear the cylinder, but the diameter looks good and I think it would seal up fine.
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Post by BFD »

:cool: Cool juliend, so you held up the 94' 125 pipe to a pre-96' 200 and the bend was too tight. Did it clear the frame alright? Were the exhaust mount brackets anywhere close? I'm fine with a little strategic denting or tweaking.
Really appreciate you scoping that out. I'd prefer a non-plated pipe for welding and heating purposes. But how much would ya want for the fmf?
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Post by Julien D »

I was looking for 50, shipped. I only held it to a cylinder outside of the bike. The bend isn't even wide enough to make it around the cylinder, much less a frame. My neighbor has a couple H bikes sitting in his garage, I can check that out a little more closely for you if you like, but it doesn't look like it would be an easy fit. Maybe with enough heat and bending, it might go.
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Post by BFD »

Thanks, if you check, let me know. But don't go to too much trouble. This is definitely my problem. I should have an e-bay pipe within a day or two, then the serious head scratching begins!!
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Post by BFD »

I got the OE 98 kx125 pipe in the mail today. It's not even close to fitting!!

Main points of interference are:

1. power valve linkage cover.

2. angle of pipe inlet is wrong by 15-20 deg.

3. length of pipe outlet is about 4" too short.

Corrections will include:

1. denting expansion chamber to clear linkage cover.

2. cut & weld inlet to correct angle.

3. cut & extend pipe outlet to match up with silencer.

Pictures to come!!
BFD
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Post by KarlP »

Good stuff.

Yeah, you knew it would not be very close to fitting.

If you correct the angle of the pipe inlet by adding a bit of length it may clear the linkage cover

On welding- The pipe material is very thin where the hangers go. If you have to weld a lot of time spent cleaning the inside of the expansion chamber will help a lot. The baked in spooge wants to bubble up through the weld.
On my hybrid I heavily tacked the right size bend/pipe to my silencer inlet. I then wrapped it with a ribbon of epoxy putty and smoothed it out. At the time I thought that silencer was going to be just a temporary job. It is still on the bike.

Have fun.
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
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Post by BFD »

Thanks for the advice Karl.

I was able to cut the inlet about an inch past the o-rings, and correct the angle by removing not very much material. I cut the upper mount bracket off of the pipe to be relocated an inch or so forward. The lower pipe mounted bracket will line up will a little persuasion. Yes, the pipe IS thinner than you would expect!

All of the pieces are ready for for tacking together, just waiting on new exhaust hangers.(old ones were past their pull date) Am using two orig upper 96' kdx mounts to fit the 125 pipe.

All frame mounts, as well as the fmf silencer location will stay the same. That way I can just bolt up a new 200 pipe if this whole thing doesn't work out so well!!
BFD
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