A path less travelled 97 kx125

[KDXGarage]

Nice! Looks great.

[John_S]

Congratulations on all the hard work paying off. I give you a lot of credit for taking a tough path and sticking it out. Those 70 number plates remind me of Ricky Carmichaels 1998 Splitfire KX 125. I remember that was the first time I saw a KX with black wheels and loved that bike.

Screenshot 2023-07-10 135146.png (1.12 MiB) Viewed 38016 times

[Ridea200]

Already typed this once, so here's the short version...
Sub-mount steering damper:
97 kx250 top triple clamp (holes ovaled out toward inside about 1mm for the 450 mount)
Brp Sub-mount for 09ish kx450f
Brp bolt on tower for 97 kx125 (trimmed to fit Sub-mounting)
Scotts damper
With all the above parts (and the mentioned mods) all that was needed was to use a spare top clamp washer to space the top clamp up, so the damper didn't bottom out on the stem.

[Ridea200]

My footpegs had seen better days, but didn't want to go with the ims pegs. After looking up what others had done, I picked up a set for a ktm. They're moose brand, have a curve to them, front to back, and are set back .25". Also, just plain bigger than stock. I used the stock pin, and spring, but had to drill a hole in the peg to capture the spring. Also, the pad area, that hits the frame, was shaved down a little so they sat at 90 degrees. The end of the peg was up/back just a little. Nothing crazy though. To top it off, I shaved down the area of the peg that hits the rear brake lever, so that its flat on the lever, and not a corner. I think a lot of that part has to do with the setback...

[KDXGarage]

Nice!

[Chuck78]

So what's the feeback on the finished product compared to a KDX chassis?
I'm considering a future project for my spare 220R engine still... A SmartCarb SC2 36 would be a very nice addition, but your carb clearance issues with the tiny PWK carbs has me wondering if a SmartCarb SC2 36 would even fit WITH frame mods. More photos of your carb mounting versus the frame would be very helpful.

I'm also curious as to the feel of the KX125 hybrid vs a 95+ KDX, particularly a KDX upgraded suspension. I'm really wondering less top heavy as a KDX. That is the big motivating factor that would make me build a hybrid vs just sitting on my spare 220 engine and being content owning 97 and '99 complete 220 bikes and perpetually modifying them.

[Ridea200]

Chuck78: I'll try to get some better pics, and measurements for you. Keep in mind, this is a 97 kx chassis, so newer ones, as far as I know, don't have the same issue with carb fitment. Also, I could have made more room, but didn't need to...That, and this is a 200. Is the 220 cylinder bigger around?
As far as handling, and such...I've been messing with sag/clicker settings a little, as they needed attention anyway. (Ill post full set-up later.) Now, it handles like I want... I mainly ride woods/desert. From what I remember, the kdx chassis was pretty good. Comfy, and stable. Not really a race bike though.
What are your plans? I would say, at this point, if you have a spare engine, do the swap. Race bike or not. I can putt with the fam, then just go race mode. This is what the kdx should have been sirca 00...

[Chuck78]

As far as handling..., it handles like I want... I mainly ride woods/desert. From what I remember, the kdx chassis was pretty good. Comfy, and stable. Not really a race bike though.

This is what the kdx should have been sirca 00...

You are very correct about that last bit especially... Too bad Kawasaki let KTM begin surpassing them in 1998 & never tried to get a foothold ever again in woods / enduro bikes. Until the last year or 3 as Kawi really began taking serious note of how popular woods / enduro racing and wiids riding has become, which is primarily dominated by European 2-strokes since the new millennium!
I'm crossing my fingers that the 300cc fuel injected 2-stroje they've been developing for a KXF chassis will be called the KDX300R for the 2024 or 2025 model year...

I'm currently gearing up for several massive winter projects, including rebuilding my '99 KDX220R with 98 RM125 forks and '01-'04 RM125 shock, and a big chunk of $$$$ in titanium parts to try and get it closer to the weight of a KTM 200 etc.

I was still very intrigued by the thought of picking up a 1996 or 2005 KX125 basket case. I've more recently learned of KX151 & KX167 engines from a big bore engine builder named Rick Petersen I believe, MAX RPM I believe is the shop name. 100 octane suggested fuel on a bored ported stroked cylinder with clearanced crankcase and re-chambered head... Wow. This sounds pretty appealing except for the $2000 price tag as they don't sell kits, they build big bore engines. The 167cc especially sounds appealing as I love the lugability of my grunty 220 far more than the lesser lugability of a KDX200H even with maximum ignition advance and a Gnarly Woods pipe... So as a trade off for weight savings and sticking with a 125 engine base, the biggest big bore stroker possible would be the goal. Perhaps it could be focused on low rpm torque porting. This would make for a really interesting build.

For now, I'm focusing on rebuilding my old KDX 220 with as much in the way of titanium parts weight savings as I can, including cylinder studs from Titan classics, brake caliper pistons and full brake hardware kits, kx500 titanium swing arm pivot bolt and suspension linkage bolts, axles, etc in order to keep the short wheelbase / steep steering angle KDX chassis, has it really does quite well. I've seen one project where a guy used a KX 125 aluminum rear subframe on a KDX E-Series. Was intriguing but I'm not sure if I would go that hardcore just to save another pound or two, at the expense of durability. Tossing the bike on its side doing rugged gnarly woods riding, the rear fender and side covers really take a beating at times. That would be an interesting project though if I learned how to TIG weld aluminum, in order to add the proper tabs and bracketry to keep KDX plastics on it.

[Ridea200]

Chuck78: No new pics, but I just looked at the carb/frame clearance again. Its probably 2-3mm. It wouldn't be hard to get more if needed though. Also, I saw in another post, that you where talking about seats. Mine is shaved to fit an 06 kxf cover. Although not as comfy as the kdx, its about as good as it gets for an mx bike. No discomfort on long rides.
As far as picking the bike up: Even though its obviously heavier than the "125", its not to bad. Other than hill climbing, I haven't crashed to much though/had to pick it up tired.
Now if I could swap in a bunch of titanium like what your planing/doing on your kdx, that would be sweet. Even with my light, damper, and big tank (and getting the suspension way more dialed) this thing doesn't feel heavy. I ride woods/desert, and have had no issues/concerns.
I haven't ridden a 220, but I don't have any lugging problems.
Never have...13/47 or current 13/50...
If you where closer, I would let you go for a rip...

[Chuck78]

@Ridea200 - how did this build turn out? You haven't updated things at all on this post since the initial few rides!

I was curious if you ended up adding mounts for the KDX radiators, or if using the KX125 radiators, how you plumbed up the left side head to radiator hose? Looking at some pictures, it looks like the left side KX radiator may require different cylinder head to radiator hose???

The next step was to get the down tube matched up. As mentioned, and can be seen in prior pics, there's about an inch difference between these frames. This is where I gained the pipe clearance. Split, and bend...

I was trying to score some cut up pieces of a KDX frame to get at least the case saver hoops, but perhaps to do the exact same as you've done here... No luck, they scrapped the frame already. Maybe there will be another.
I think I'll go about grinding the welds off where the cradle tubes meet the center front frame section from below, and heat up and bend the tubes back to get the adequate clearance to the pipe. Then, I'll cut the center frame member and extend it rearward with some added metal, and possibly cut the front section on the sides to pull it back as needed.

Looking at the KDX frame where the cradle tubes meet the center section, the center definitely kicks back at the bottom, curving rearward to meet the cradle tubes which definitely sit 5/8" or more rearward vs this '97 KX125 frame I've picked up.
Using the KX lower engine mounts to make a triangulated brace up to the shock mount crossmember to hold the bottom of the frame steady and support it, then once I have the front upper portions of the engine cradle free from the center portion of the frame, I'll see if I can heat both cradle tubes in the area I'd like to bend them rearward, and carefully push them back to where they are needed to be.
Then modify the section they were formerly welded to in order to bring it back as needed, without having to make pie slices out of the tube to fold it back forward to catch the frame where it gets welded back to.
I may try and get a large diameter steel pipe section as well, or perhaps making a jig for the tubes to glide into, with the curvature desired possibly?

Looking at the 94-98 KX125, I think perhaps the cylinder is angled forward/downward more than the KDX engine's cylinder is positioned, and that may be why the front of the frame is extended a bit perhaps, causing this KDX exhaust clearance issue?
Interestingly, a KDX (online) friend in New Zealand has a '96 KX125/KDX220 hybrid, and he did not modify the frame at all to clear his old FMF Woods profile pipe! I believe he used something like an FRP Torque Ring to bring the pipe just a hair further back out of the cylinder, but the o-rings are still both within the cylinder exhaust flange on his with the KDX pipe clearing... I'll have to double check back with him on the details on pipe and spark arrester used.

Another note - the '99-'02 frames are VERY similar to the 97 and 98, probably the 95-96 as well, which are an improved version of the '94 of the same parts fitment. So much so that one can fit the 99-02 engine, seat subframe and all rear plastics and airbox + seat tank and shrouds and convert a 98 etc to a 99 model... the shroud mounts must be ground off the 94-98 frame to fit the 99-02 tanks, but they are very much the same otherwise. 99-02 had a more arched shock crossmember on the bottom side so that no clearancing as you've done would be needed, they came with a PWK36 which is the larger of the older style long body PWK carbs, externally larger than the PWK35 that older KX125's and KDX's came with.



After looking over my frame quite a bit, it was good to read your build again for some further insights and comparisons. Thank you for documenting this!




]
Due to picking up a rare purple oversized tank with integrated shrouds for the 94-98 KX, and a few other hard to find 94-98 KX aftermarket parts (Acerbis spark arrestor, Works Connection frame guards, AC Racing aluminum seat subframe), I started snatching up bits and pieces starting with a '97 KX125 frame and swingarm, complete rear brake, and some plastics and a seat... I'm on hold for now other than the rare nights at home solo when I get to tinker a little, like tonight! (renovating another house to sell, once sold, the bikes and Toyotas get the attention and finding needed!)
I've got a spare 220 engine for it, who's cylinder will get sent out for some professional porting & replating, + some Showa RM125 shocks and 2025 Showa KX450X forks (race team take-offs to run their professionally set up 2024 versions.