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I tried to locate a similar bit with no luck. I had a machine shop that was only willing to cut the cases with something similar. They considered fabricating a 15 mm pilot to go all the way through both sides welded to a 17mm reamer or bit to follow it through. Never got a price, but he stated that it would most likely be cost prohibitive. I could tell the guy really wasn't into the job, so I decided to tackle it myself. Again, it is possible to do with a hand drill and get very very close.

Here is a quick update on the process. I haven't had as much time to work on it lately. I now have the swing arm mounted to the case and I'm in the process of determining the fitment of the carburetor and the pipe. I have fabricated the motor mounts. The bottom I used the KX 125 mounts that I cut off cut to size and the top I had to make from scratch. Not welded in yet.

I spoke with David at lectron and he recommended that I use the shorty carb that is used on the YZ. I'm still worried about the lack of space for the card to slide in. The kx250 boot matches up much better than the KX 125, but there is very limited space. It appears that I will have to either squish the boot back about 20 millimeters or cut into the boot to make it shorter. Something similar to Tioli's mod. I do not have the carb in hand yet so time will tell.

Another minor issue is the KX 250 silencer does not slide in the pipe quite as far as I'd like. That seems very minor at this point. I'll deal with that later.

It's riding weather here and I'm getting anxious.

The new drill is 17 mm diameter with a 15 mm pilot and is long enough to drill the case in the frame all the way through from one side. This enables you to use the frame as a guide and align the holes with the frame. I have done 2 with it so far and have another ready to drill.

As far as the silencer and exhaust not overlapping very mouth it shouldn't be a problem as long as they overlap by say 5mm.
Go to a specialist hose place and get a length of high temp silicon hose with the same Ida as the exhaust and just have it cover both with good clamps and it's not going anywhere or going to cause a problem.

Two stroke exhaust should hang loose. If you try and make it ridged it will brake.

JTSDAD wrote:The new drill is 17 mm diameter with a 15 mm pilot and is long enough to drill the case in the frame all the way through from one side. This enables you to use the frame as a guide and align the holes with the frame. I have done 2 with it so far and have another ready to drill.

Do you have a picture?

If you are using the frame as a guide, are you welding in the mounts first?

Tedh98 wrote:

JTSDAD wrote:The new drill is 17 mm diameter with a 15 mm pilot and is long enough to drill the case in the frame all the way through from one side. This enables you to use the frame as a guide and align the holes with the frame. I have done 2 with it so far and have another ready to drill.

Do you have a picture?

If you are using the frame as a guide, are you welding in the mounts first?

I was wondering the same thing myself. I also noticed that B737driver also said that he welded in the rear mounts? I was under the impression that the motor mounts get welded in last, after pipe/airbox/carb/gas tank clearances were all checked.

Also, JTSDAD - Where did you get this bit? I did not get a chance to check, but I believe an intermittent drilling operation may be required before reaming to 17mm. I did not think that reamers were supposed to remove very much material, maybe .010"? I was planning to buy a bit that would get me closer to 17mm before I ran the reamer through. I know that charts exist online that give you recommended hole sizes, before running a reamer. Did you open the hole up any before reaming? Or does that bit do a good enough job that its not needed? I'm thinking that the aluminum will likely be easier to cut than steel...

I was wondering the same thing myself. I also noticed that B737driver also said that he welded in the rear mounts? I was under the impression that the motor mounts get welded in last, after pipe/airbox/carb/gas tank clearances .....

I have not welded in the frame mounts yet. I have them rough cut (too long) and I'm waiting for the carb to arrive for the precise measurement. I will say this however, I've got the pipe mounted up and connected to the top bracket it really looks at home there. Hopefully it will be the carbs home as well. One can dream right?

Right on man, I misunderstood. I hope it does end up fitting nicely for you.

I'm jealous...dying to get a KDX so I can go to town on mine!

Tyl3r wrote:

Tedh98 wrote:

JTSDAD wrote:The new drill is 17 mm diameter with a 15 mm pilot and is long enough to drill the case in the frame all the way through from one side. This enables you to use the frame as a guide and align the holes with the frame. I have done 2 with it so far and have another ready to drill.

Do you have a picture?

If you are using the frame as a guide, are you welding in the mounts first?

I was wondering the same thing myself. I also noticed that B737driver also said that he welded in the rear mounts? I was under the impression that the motor mounts get welded in last, after pipe/airbox/carb/gas tank clearances were all checked.

Also, JTSDAD - Where did you get this bit? I did not get a chance to check, but I believe an intermittent drilling operation may be required before reaming to 17mm. I did not think that reamers were supposed to remove very much material, maybe .010"? I was planning to buy a bit that would get me closer to 17mm before I ran the reamer through. I know that charts exist online that give you recommended hole sizes, before running a reamer. Did you open the hole up any before reaming? Or does that bit do a good enough job that its not needed? I'm thinking that the aluminum will likely be easier to cut than steel...


Sorry guys I think that I have left out the fact that I put 1991-1994 KDX250 motors into 2003 KX250 frames. The motor mounts line right up with no modification. I just have to do the swing arm mods and some changes for the head stay.
I use a 17mm drill that has a 15mm pilot on it. I don't use a reamer.
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I guess I wasn't clear enough.......the motor mounts are welded in LAST.......after airbox (a real pain in the a**), pipe fitment, and most importantly getting the countershaft sprocket lined up.

I've been slacking on the updates, but it's finally finished.






Decided to keep the lights.....after all its a KDX at heart.

Thanks to all who helped out with ideas and suggestions.

Can't wait to get it dirty!

droooooooooooool

looks awesome man! damn fine job you did there!

I really like how you kept the lights, the taillight looks real sleek. I keep going back and forth on whether or not to keep the lights on mine lol

What did you end up doing to get the air box, boot, and carb to work together? And what radiator hoses did you use?

Thanks. Can't wait to ride.

The air boot was definitely the hardest part of the build. I used a combination of ideas and suggestions from other hybrid "veterans". The KX 250 air boot lines up much better than the 125....so I went with that. Thanks KX200. It still did not provide enough space for the carb, so I took Tioli's advice (another thanks) and cut of the lip. I then used a dremel tool on the inside of the boot to form a notch for the carb lip to sit in. This got it to where it was manageable. I did purchase a Lectron carb which was "thinner" than my RB'd carb. Not sure if this is the best (definitely not the most cost effective) way to go, but I'm happy with the results. The Lectron seems to make power more linear. Not as big of a hit, but the power is still there. I think it will work great in the technical stuff.

That bike looks awesome. If Kawai were brave enough to re-introduce the KDX I bet it would look a lot like that! Yamaha rolling out the YZ250X fosters some hope [emoji120]


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Thanks and I agree. Kawi's half-hearted venture back into the off road market with the '08 KLX 450R was DOA. Can't wait for them to get back on board and build a proper 2 stroke.

Wow that does look fresh and clean. You should be proud of that, well done.

B737 what fuel rod are you using on the Lectron also who makes the led tail light

kx200 wrote:B737 what fuel rod are you using on the Lectron also who makes the led tail light

I'm using the fuel rod that came with it. I did not purchase any extras. I'm not at home now and can't check for the exact specs. They were very helpful over the phone and basically they machined it very similar to the YZ shorty style since i had very little room. I like it so far.

The taillight is from eBay. Think it was $20 or so shipped. Easy to find. Search for ktm style taillight assembly.