'04 KDX 200 to 04 KX 125 hybrid build

B737driver · Post by **B737driver** » 11:14 pm Aug 31 2015

Tedh98 wrote:I bought this bit on eBay years ago and used it for the first time not long ago. Made the job really easy.

hybrid drill bit

That's exactly where I saw it. It's been driving me crazy trying to remember where... thanks for restoring my sanity.

KarlP · Post by **KarlP** » 09:05 am Sep 01 2015

You can hand drill it, no problem.

Keep in mind the order of things -
Swingarm bolt drilling
Set engine left/right for CS alignment
Mock up carb and exhaust
The rest of the motor mounts are last. If you do them too early you may find problems getting carb/exhaust right

Tedh98 · Post by **Tedh98** » 09:47 am Sep 01 2015

^ all good advice.

One thing I would add on the CS, you also need to watch the alignment relative to the swingarm bolt. If the engine is tilted too far down or up, you will have accelerated wear on the swingarm slider.

If you happen to use a PC 2 pipe on the '04 frame, you should be able to align the engine without having to modify the pipe in any way.

B737driver · Post by **B737driver** » 07:34 pm Sep 01 2015

Excellent... Thanks for the tips guys. Slowly getting through it. I started drilling the cases today. I got ahold of some standard drill bits but I'm missing the one for the final cut. I started with a 41/64th (16.2mm), then a 21/32nd (16.6mm), and the next size I had was an 11/16th (17.46mm). I decided against the 11/16th and have a 43/64th (17.06mm) coming tomorrow. The cutting was slow with the occasional wrist breaking grab of the bit. I cut all the way through, rather than one side then the other. I think it's close, not perfect but close enough. One more cut tomorrow and I get to move on to the next step.

kenpowell · Post by **kenpowell** » 03:44 pm Sep 02 2015

I used a 17mm reamer for the final cut when I bored the cases. I like the 15mm/17mm drill bit that Ted used even better.

B737driver · Post by **B737driver** » 12:48 pm Sep 03 2015

Alright. I've got the cases drilled to 17mm. The cut is not "perfect" but it is very close. To anyone that got the bore perfect with a hand drill...I applaud you. Not really sure if I should attempt taking a little more off of one side, or just rolling with it. Comments? I guess the question is what affect the very slight angle will have over the length of the chain to the rear sprocket.

Anyway, I've got the swingarm bolt through, it's in the frame, now I am mocking everything up. I'm close to the swingarm and bushing cut.

Looks like my FMF woods may need a little alteration with a hammer, or maybe it's time for a new pro circuit.

Verdict still out on the carb....
1. Kx 125 or 250 boot with aluminum ring on the carb
2. " " boot with kdx boot cut and placed in the larger boot
3. Kdx boot with alterations made at the airbox

That's where I am.....Pics to come

Tedh98 · Post by **Tedh98** » 01:33 pm Sep 03 2015

B737driver wrote: Verdict still out on the carb....
1. Kx 125 or 250 boot with aluminum ring on the carb
2. " " boot with kdx boot cut and placed in the larger boot
3. Kdx boot with alterations made at the airbox

I like #2 the least.

Regarding #1 and #3, can you do both yourself or would you have to have someone else do #1? #3 is something that most anyone should be able to do, but #1 isn't.

If it were me, I would wait until you got the engine in and got your CS sprocket all ligned up (both left to right and tilted up/down) and then see which approach is going to work the best.

B737driver · Post by **B737driver** » 09:35 pm Sep 03 2015

Leaning towards replicating Ted's mod with the kx "filter holder". No way I could do the other one. Do you recall the thickness of the sheet aluminum used? Here's why the 125 boot will not work.

As you can see, nowhere close to lining up.

Pretty slick work with the router as well. I'm guessing that was a table router?

B737driver · Post by **B737driver** » 09:59 pm Sep 03 2015

This is what I came up with .......countersprocket in position, left to right that is. Still working on the up and down. The left is 53.5 from case to frame. The right is 51.5.

This is the math I used to come up with the size of cut on the bushings. If anyone is ever at this point, hopefully they will be able to decipher my hens scratch.

I'm considering varying the cut on the swingarm as well. The bushing on one end and thick washer on the other end extend 3 mm beyond the swingarm, soooo 53.5-3.0=50.5 on the left and 51.5-3.0=48.5 on the right.

Tioli · Post by **Tioli** » 07:24 am Sep 04 2015

I had my share of difficulty with the positioning of the air box.

All about it. Halfway down this page
http://www.trials.com.au/forum/viewtopi ... &start=220

Exiting times building a hybrid

B737driver · Post by **B737driver** » 10:52 pm Sep 14 2015

I finally got the bushings and swingarm cut. Took them into a machine shop and the guy cut them on the spot. Best $20 I've spent in a long time. After some minor trimming and grinding at home....it's in. Appears to line up well with the rear sprocket. Now it's time to start mocking things up.

Post by **Tyl3r** » 06:18 am Sep 15 2015

Very nice! How did you ensure the sprockets were in line when you were in mock up? Lay the chain across and do a visual?

Before I pulled my KX motor, I wanted to make some sort of measurement from the counter-shaft sprocket to a reference point on the frame. Then I could try to put the KDX motor in the same position to start out. However, I forgot to do so. I may drop it back it and try to do something, I dunno... you think its necessary?

Run into any issues trying to get the bushings to the right size? I was thinking about mocking up with the bushings that are in there now, and once I get em perfect, have the machine shop at work turn down a brand new set to the correct length. Seems like you may have done the same?

What conclusion did you come to with the air box? I saw in someone else's build thread that they used the KDX air box and everything. They had to trim some areas off the bottom of the KDX box to get it to mount right, but closed those sections off with aluminum plate and silicone. If I have a KDX air box on hand when I'm mocking things up, I may try that out and see how it goes. I like how the KDX box is more "sealed up" (lid on or not) for the type of riding I do. I'm afraid I'm going to drop into the creek one time and pull water through the louvers in the number plates. The KDX box is at least all closed up on the sides of it.

Tedh98 · Post by **Tedh98** » 06:41 am Sep 15 2015

Tyl3r wrote:Before I pulled my KX motor, I wanted to make some sort of measurement from the counter-shaft sprocket to a reference point on the frame. Then I could try to put the KDX motor in the same position to start out. However, I forgot to do so. I may drop it back it and try to do something, I dunno... you think its necessary?

I don't think that would have helped because the engines are different. Any reference points you would have made on the KX wouldn't have meant anything when you tried to apply them to the KDX / KX combo.

Tyl3r wrote:What conclusion did you come to with the air box? I saw in someone else's build thread that they used the KDX air box and everything. They had to trim some areas off the bottom of the KDX box to get it to mount right, but closed those sections off with aluminum plate and silicone. If I have a KDX air box on hand when I'm mocking things up, I may try that out and see how it goes. I like how the KDX box is more "sealed up" (lid on or not) for the type of riding I do. I'm afraid I'm going to drop into the creek one time and pull water through the louvers in the number plates. The KDX box is at least all closed up on the sides of it.

I remember that build as well. Pretty sure that was an older KX. With the newer KX's, the side panels fit into the airbox. So if you could use the KDX air box, you'd then have to deal with how to fit the side panels. I think it would be easier to close up the KX airbox.

Post by **Tyl3r** » 09:43 am Sep 15 2015

I was just going to measure the distance from the frame to the outside edge of the drive sprocket. Then when I put the KDX motor in, I would adjust it side to side to have put the drive sprocket in the same spot. I would think that would pretty much put the motor right where it needs to be, then do a check with the chain laying across both sprockets. I got the idea from seeing a photo in someone else's build where they had a piece of bar stock clamped to the KDX frame, then used a feeler gauge to find the gap between the bar stock and the drive sprocket.

And I see what you are saying about the airboxes. I haven't tinkered around with a KDX for some time now, didn't realize how those ones mounted to the subframe. I did see how the airbox mounts using the side panels into the subframe on the KX.

Tedh98 · Post by **Tedh98** » 09:47 am Sep 15 2015

Tyl3r wrote:I was just going to measure the distance from the frame to the outside edge of the drive sprocket. Then when I put the KDX motor in, I would adjust it side to side to have put the drive sprocket in the same spot. I would think that would pretty much put the motor right where it needs to be, then do a check with the chain laying across both sprockets. I got the idea from seeing a photo in someone else's build where they had a piece of bar stock clamped to the KDX frame, then used a feeler gauge to find the gap between the bar stock and the drive sprocket.

And I see what you are saying about the airboxes. I haven't tinkered around with a KDX for some time now, didn't realize how those ones mounted to the subframe. I did see how the airbox mounts using the side panels into the subframe on the KX.

Gotcha, that makes sense. I was thinking more about the tilt of the motor since that is less straightforward.

On the airbox, the '03+ fenders fit tight to the airbox. You'd have to deal with that as well if you tried the KDX airbox.

B737driver · Post by **B737driver** » 09:49 am Sep 15 2015

I did measure, with the KX motor, the distance from the center of the sprocket to the weld in the center of the frame closest to it. My thinking was, that will get my left/right correct. I based my measurements for the bushing cut off of this.

I'm no machinist, but I got to see the guy do his work. He locked the bushings into place on a machine that would spin the bushing, then used a cut off wheel. Then some minor work on the grinder and a little cleanup with a file.

Airbox is still up in the air for now. I agree with Ted on trying to fit the KDX airbox. I purchased a 2004 KX 250 boot and it aligns much better than the 125 boot. Still not perfect though. I am now considering a Lectron carb. This is the setup KX200 has. Lectron has or will manufacturer a 36mm carb with the "bell" that is larger diameter to fit the KX carb boot. I am leaning this way, but it's not cheap. I just hope that I wouldn't miss the RB modified carb.

Got a week or so until I can get back to work on it......so more research and parts ordering.

B737driver · Post by **B737driver** » 09:43 am Oct 01 2015

Well I'm finally back at it......

I called David at Lectron. He is making the thinnest carb possible for me. It's actually off the specs of a YZ 125 for overall width (think he said 86mm) and having the spigot (engine side) at 42mm outside diameter and the bell (airbox side) at 60mm od. The bell side is 2 mm smaller than the KX 250 boot, but it allows me to cut the boot back a little if required. Looking at it, it seems as though the boot will have to be pushed back around 20mm to get it to fit as is. Is that what you guys have done?

Also looks like I'm going to loose my V_Force 3 reed cage for the thinner stock cage. Every mm counts at this point. What reeds are recommended for best performance on the stock cage?

Tioli · Post by **Tioli** » 09:36 am Oct 02 2015

Don't ditch the VFORCE. Can be done had the same problem. Page 13 for the details but what basically happend is the bellmouth resess for the clamp was cut off then a new flat area for the clamp was cut in. As the recess for the KX is larger when it's cut off the KDX carb fits right in perfect size. There are few other things to compensate but that's it.

JTSDAD · Post by **JTSDAD** » 07:53 pm Oct 03 2015

Tedh98 wrote:I bought this bit on eBay years ago and used it for the first time not long ago. Made the job really easy.

hybrid drill bit

I was going through this site and I saw this build what was more interesting was the drill bit that I had made years ago and sold on ebay. I tried to find someone with one but had no luck and ended up making a new improved version.
Good luck with the build, it is looking good so far.

Post by **Tyl3r** » 06:31 am Oct 05 2015

JTSDAD wrote:
Tedh98 wrote:I bought this bit on eBay years ago and used it for the first time not long ago. Made the job really easy.

hybrid drill bit
I was going through this site and I saw this build what was more interesting was the drill bit that I had made years ago and sold on ebay. I tried to find someone with one but had no luck and ended up making a new improved version.
Good luck with the build, it is looking good so far.

details on this bit that you speak of?

KDXRIDER.NET

KDXRIDER.NET