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Has anyone ever done a direct comparison of the weight of say a bare '95-'06 KDX H-series frame or frame + swingarm vs a KX125 frame with seat subframe & perhaps with swingarm?

I'm really fascinated by the thought of building a '96-'98 KX134 or KX139 woods bike, and also lightening up and modding my 220's as much as possible. After brainstorming whether or not the '99-'02 or slightly longer '97-'98 KX125 swingarm could be made to fit the H-Series reasonably easily & well, and previously having thoughts of how to mod the KDX frame to fit a modified aluminum seat subframe from a & '99-'02 or '92-'93 KX125, I figured I'd better hold off on all that extensive work and first look at the end result of how much the base KDX frame weighs vs the KX125...

I know the KDX hybrids really on a scale only weigh about 5lbs less than an H-Series KDX, but the 5lbs is a lot of weight up higher with thinner (less comfortable!) seat foam, smaller fuel tank, and aluminum seat subframe as well as fork swap weight savings with inverted forks and aluminum steering stems vs swapping the hedty steel KDX/KLX stem in place of the lighter KX aluminum stem for KDX frame use - there are now better alternatives to use other aluminum steering stems, for KDX fork swaps).

Really the forks and steering stem likely amount to 55%-70% of the weight savings I'd imagine...
One guy here in the midst of a rebuild did weigh his KDX frame recently, but did not have a KX frame to compare.

Thanks in advance!

I'll keep this in mind, especially as the season winds down. I need to do a teardown/inspection on the hybrid now that it's got a good amount of trail time.

Ridea200 wrote: 11:22 pm Aug 22 2024 I'll keep this in mind, especially as the season winds down. I need to do a teardown/inspection on the hybrid now that it's got a good amount of trail time.

Thanks!

BUT.... The season isn't winding down, it's just starting in a lot of areas in the Northern Hemisphere! This summer has been so hot that I hardly have ridden since the cross country street bikes trip in May, with mid June through mid August being in the mid/upper 90's the majority of the time... Now through November is the good time, and starting back up in March through mid June!!!!!!

Granted all those dead downed oak leaves do make the trails more slippery even when dry, late or early in the season...

LoL true. It's been like that here as well. Fire season...We did just get some rain the other day tough, thank the Lord.
I'll see what my riding buddy's are up to...If nobody's interested, I'll go ahead and get after it. I'm curious now, as well.

There's a few on ebay right now. Might be able to have the seller(s) check? One with sub frame, one without. Would be faster than waiting on me...

Have you by chance gotten into your bike for an off-season rebuild yet? I'm really as to the weight of a KX125 frame vs the KDX frame.

I bet most of the weight reduction between the two bikes is #1 engine weight difference
#2 fork weights
#3 thinner seats 1999-2005, less foam
#4 smaller lower gas tank (less fuel weight, slightly less plastic weight (negligible))


Others:
More race spec bolts (dished out heads)
Slightly thinner rear rotor and shaller diameter rotor bolts
No speedo drive or odometer
No headlight
Aluminum wheel bearing center hub spacers and slightly lighter front hub shell (4 ears for rotor mount vs 360° full flange on KDX)

I would expect the KX frame to only weigh perhaps 2lbs less than a KDX frame, partly due to slightly narrower width up front, but mostly due to the shorter seat subframe length and 1999+ aluminum subframe construction.

The frame geometries are nearly identical KX125 vs KDX, 1997-2002 got a very slightly longer swingarm by a negligible amount (additing a chain link length?) & 2004-2005 got a fair bit longer swingarm, 2003-2005 got lazier steering angle.

The 1994-1998/1999-2002 KX125 got a significantly taller ground clearance however... I suppose with taller suspension but nearly the same wheelbase as the KDX, figuring in the fork rake angle, the KX125 frame IS a bit more compact front to rear then, since taller forks anhled forward would increase the front end length, therefore if wheelbase is almost identical to the KDX, the KX frame must be a bit more compact front to rear.
The KX250 swingarms were longer I believe, their published wheelbases were slightly longer most years vs KX125, but I would need to confirm part numbers. The fronts if the frames are very similar and take the same plastics, but engine mounts and cradles are definitely different, so perhaps rhe length is in the front end as well as swingarm???
Aluminum subframes on 99-05
Shorter subframes (no taillight to hold up)
OEM exhausts (a non-issue on a KDX as almost all are running aftermarket)
1 cylinder head headstay mount vs 2
Coolant overflow reservoir
Larger shrouds on the KDX for better low speed cooling

I've emailed a seller on eBay, the ONLY seller who had a KX125 frame WITH seat subframe listed in the same auction, to inquire if they'd weighed the frame to get the listed shipping estimate, and if they had the swing arm and linkage or any other parts.


If I could get a frame swing arm linkage and seat all from one person, I might just make an impulse buy! IF the frame were actually noticably lighter...

I remember someone once saying that the 2003+ was an easier KX125 to convert than the his other conversion 1999-2002 KX125.

In general, a KX125 frame and subframe are quite a bit lighter than a KDX200/KDX220R frame. I own and have picked up both of a few models. I have not and can not put them on a scale.

KDXGarage wrote: 08:42 pm May 17 2025 I remember someone once saying that the 2003+ was an easier KX125 to convert than the his other conversion 1999-2002 KX125.

In general, a KX125 frame and subframe are quite a bit lighter than a KDX200/KDX220R frame. I own and have picked up both of a few models. I have not and can not put them on a scale.

The 2003+ KX's have the lazier steering angle and longer wheelbase that deters me from most modern bikes though, as well as having significantly lower ground clearance... And each year '03/'04/'05 have a unique swingarm and linkage to that year... I really really like the '97-'02 KX125 geometry, just a hair longer swingarm than the KDX, & basically the same steering angle (26° vs KDX @ 26.5°).

The Beta 200RR Race (& 125RR) along with the Yamaha YZ125X and YZ250X are the only modern machines which I really care for the chassis geometry on tbh...