KDX frame weight vs KX125?

[Chuck78]

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!

[Ridea200]

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.

[Chuck78]

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...

[Ridea200]

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.

[Ridea200]

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...

[Chuck78]

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

[Chuck78]

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...

[KDXGarage]

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.

[Chuck78]

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...

[Kx200x]

I've got a 99 kx125 with an e series engine. I've had a lot of dirtbikes and it is one of my favorite except the powervalves that break and difficulty getting good cylinders for the e series. I put kouba links in the linkage that lowered it a hair but it turns really well now and being short helps me in the woods that it lowered the seat height a little. I installed A pro circuit h series pipe with a 99-02 pro circuit kx250 silencer fit well and woke it up significantly. I also made my own divider plate installed in a 36.5mm bored out pwk carb. It has a boyeson rad valve with new 2 stage reeds. I also added Jaguars cdi box and a cr coil pack and it significantly strengthened the spark output and let's the bike rev further and added a little grunt down low. After I first installed it I pressed the kill switch to shut it down and lifted off when it normally would have shut down but the bike started up again. I've got to hold the kill switch down longer to get it to turn off lol.

[Chuck78]

Just about any damaged KDX cylinder can be repaired and replated, so finding a good cylinder isn't too much of an issue unless you are looking to do it on a major budget and run a used cylinder without re-plating it.

The main thing I wanted to comment on for your sake is that you should be running the expensive BDK billet steel power valves. There are several companies that make them, I noted the cheap ones were still made out of aluminum, when they should be steel, so perhaps you should change the source of where you are buying those subport drums from.

I've got a Jaguar CDI and the Honda coils, but as with most of my favorite KDX parts, I've got them on the shelf awaiting time to do major rebuilds on both of my bikes which should be happening this winter now.
Did you have to do much adjusting on the switches on the CDI to get it tailored to your needs? Did you keep it at the stock setting that it was shipped with? What setting are you running the switches in?

[Chuck78]

Did you by chance ever weigh the frame of your KX125 versus the original KDX frame?

I still am looking out for a 96-98 KX125 most likely for a hybrid build, slight chance I would go off on a tangent and do a 98-02 KX144 (more likely a 134cc) woods ported build with the cylinder base cut down to lower the ports for more torque as well as a major porting job.
The ability of the 220 engines to lug is something I rely heavily on though, a 144 would really need to rev out still to make anywhere near the same power at KDX 200 RPM ranges, the 220 torque is out of the question from a 144 cc...

I could probably find a '96 or '97 as an abandoned project as crank parts for the 94-97 are tough to come by versus 98 and up. I might run a 99-02 as a hybrid, they have nearly the same geometry, but I really like the styling and the seat on the 94-98 generation.

[Kx200x]

Try the jaguar cdi. The settings are east to do. It makes the bike faster and idle stronger. 1st switches left down and right up. Right switch middle up was my base then I played with it. Start there and you will notice an improvement right away.

[bufftester]

I don't remember the exact weights, but when I did my hybrid (2001 KDX220 and 2001 KX125) it wasn't as much of a difference as I thought it would be, something like 10 or 15 pounds on the entire build.

[Chuck78]

I don't remember the exact weights, but when I did my hybrid (2001 KDX220 and 2001 KX125) it wasn't as much of a difference as I thought it would be, something like 10 or 15 pounds on the entire build.

I had read some weights posted on here somewhere which stated one member's hybrid build only ended up being 5lbs lighter than their identically equipped KDX (skid plate, radiator guards, same pipe, hand guards, etc), but that the perceived weight, the feel of the bike, despite very similar geometries, was definitely more lightweight feeling - I will say it's almost certainly due to lower fuel tank and smaller fuel capacity, thinner seat foam shaving another bit of top-heavy weight off up high, as well as the atrociously heavy H-Series 43mm conventional forks (4lbs heavier than KYB inverted open chambers 2000's KX 48mm / 2004 YZ 48mm / KLX 300 43mm etc all being 4lbs +/- lighter than the OEM KDX forks 89-92/95-06.
The slightly more slender frame and shrouds configuration especially on the last gen KX125 2003+ also adds a significantly more nimble agile slender feel to the machine.

All that being said, I am still keeping my eyes out for a 96-98 KX125 (or a deal in a '99-'02) to either build a hybrid or try for a 134cc woods ported build (the KX 125 engine is 12lbs lighter, the biggest difference, or else just go for a 220 hybrid a 98-02.
At the same time, I've amassed a large pile of weight saving parts for my 220 rebuilds to where I may be dropping 13.5-16lbs off the stock weight of the KDX 220, so I'll see how that will do...the Showa or KYB closed chamber forks only shave about 2lbs maximum off the fork weight vs KYB open chamber 48's, so the OC 48's may be the best thing for a lightweight woods build unless closed chamber fade resistance is really truly needed for the rider & terrain. Knowing this a few years ago, I would have been collecting those instead of Showa Twin Chamber forks !

[Chuck78]

Has anyone else had an opportunity to weigh a bare KX125 frame with seat subframe yet???


At some point soon, I'll likely be buying a 95-98 KX125 frame, as I have been compiling a few parts already to fit it. First were some purple shrouds to fit this generation, & now what really set me off was finding a purple Acerbis oversized desert tank with integrated shrouds, fuel carried in the shrouds as well with the filler cap at basically the same height. Unlike the KDX or the other types of oversized KX tanks for the perimeter frame models (which expand downward towards the engine in a few small areas but largely carry all the extra weight up top including requiring modified (trimmed smaller) shrouds, this Acerbis integrated shroud desert tank carries the additional fuel weight at the same height as the stock 2.2 gallon KX tanks. It does, however, make it as wide as the KDX in the rear of the shrouds, so you lose that narrower feeling KX chassis perk in the knee area, as well as carrying a bit more of the fuel weight out to the sides slightly further. At least it keeps a good portion of the additional weight down low, however.

Also scored was an aluminum aftermarket AC Racing seat subframe, as the '94-'98 KX originals were steel, although this may actually be slightly heavier than stock - but is substantially stronger. Lastly, a NOS, still in box Acerbis 035 spark arrestor for 94-98 KX250, the application used in hybrid builds in conjunction with a KDX 200H/220 pipe.

Once I get a frame here, or a complete bike if I find a good blown up bike deal, I'll be sure and weigh things to compare to the posted KDX frame weight of 3 lbs in another post in this sub forum.

This time around I'm likely building a 220 hybrid, although I still am very fascinated with trying to maximize the power out of a '98-'02 134cc KX 125 engine, probably with a 99-02 cylinder and '99 head or aftermarket head with a squish/dome cut similar to the '99 or '95-'97, wide squish for combustion timing more conducive to bottom end and mid-range power output vs high end, as well as pushing about 195-200psi cranking compression / 90-95 octane required, to squeeze a little bit more power out of the small bore.

[Chuck78]

Has anyone weighed a KX125 frame (with seat subframe) to compare to the KDX200H frame weight?



I still haven't cracked into a full rebuild & major upgrade of my '99 KDX220 yet, but I'm still slightly considering picking up a '96-'98 KX125 chassis for a hybrid build,

Several people stated that the KDX200/220 hybrid builds only end up at around 5lbs lighter than the trail-ready KDX with the same parts (aftermarket exhaust, bark busters, skid plate, radiator/pipe guards, headlight, aftermarket handlebars, etc). I'm not certain if that's meaning a KDX with a newer fork swap upgrade or not.

*KDX aftermarket exhaust (-4.5lbs+) (any trail-ready KDX is highly likely to be running full aftermarket exhaust at this point in the bike's 19-36 year history
*1999+ KX or other modern fork swap (1.1lbs - 2.8lbs on a closed chamber fork swap, 1lbs-4.8lbs savings on an open chamber KYB fork swap).
*aluminum KX brake pedal and shifter lever -1.1lbs vs stock KDX steel versions,
*Trail Tech Yamaha YZ kickstand mods to fit the KDX -1.25lbs

+KX seat subframe doesn't extend out as far in the rear, frames are slightly narrower than the KDX
+the '99+ seat is a typical modern seat that's not for full time sitting or all day riding comfort (half the thickness of foam, saves up to 1lb,),
+& far more of the KX bolts have dished out race spec heads to shave probably 0.50 lbs more off the bike...
+the KX triples all have aluminum steering stems, so shave another 0.50 lbs off,
+the 2.2 gallon fuel tank is slightly lighter and won't allow the KDX's 2.91 gallons capacity (0.60 gallons extra fuel weight all up high)....
+Also, the KX frames are missing the KDX's case saver frame hoops... I'd weld these onto a KX frame or fab my own
+the KX shocks weigh a bit more as they are longer and larger diameter at 46mm for older models and 50mm for newer models.

All the above total up to about a 5lbs difference or greater there... The slightly lower fuel tank, narrower frame, shorter rear subframe seem to make up a lot of that. The KX vs hefty '89-'92/'95-'06 KDX forks save more weight, 1lb 96-98, more weight savings on 99+ forks...
I believe the KX also squeezes the space down top to bottom a slight bit better (lower fuel tank / higher ground clearance), for a slight bit tighter mass centralization.
So if you're really looking to save every bit of weight while upgrading fork and shock as well as gaining ground clearance at the expense of a taller seat height, and a slightly longer swingarm for better hill climb stability, the hybrid will get you all these upgrades...

The '96-'02 KX125 geometry has a much higher ground clearance at 15"+ vs the KDX & 2003+ KX @ 13.75" or so, & the steering angle is even steeper on the '02 & earlier KX125 ('90-'02? definitely '94-'02) @ 26° which makes for a very excellent fast sharp steering for tight woods riding. The '97-'98 swingarms are slightly longer by an extra chain link 18mm extra length, and taller box section for more rigidity. That'll help by extending the short wheelbase on the steep hill climbs since that's the KDX200 & '96 & earlier KDX/KX125 hybrid's only weak point of the chassis geometry handling - steep hill climbs. Handling everywhere else in the woods is super crisp and responsive...[/size]

Well... I'll soon be able to provide a KX125 frame weight myself, after no one else has chimed in here or elsewhere on the big comparison question!




...after finding some rare aftermarket parts (purple Acerbis KX desert tank, AC Racing aluminum KX seat subframe, Acerbis 035 KX250 spark arrestor, and Works Connection '94-'02 KX125 frame guards, + an additional $183 later, I now have a '97 KX125 frame in transit.... so I'll finally be able to weigh the differences in frames, mid-period '95-02 KX125 vs perimeter frame '95-'06 KDX200/220... Building a hybrid from parts is a costly approach, however it will be built with the exact parts I choose, and all good condition vs buying a clapped out KX125 roller

Others have said that the KDX frame @ over 30.3 lbs is quite heavy, but the KX frames are constructed nearly the same as best as I can tell, and both are made of the same steel per the Kawasaki annual sales brochures. An E-Series KDX frame is likely lighter, but even lighter are the modern KTM frames built similar to a KDX200E or 1988 KX, but lighter... I've seen many examples of cracked KTM enduro bike frames, but never have I seen a cracked KDX frame... KTM builds things very light (i.e. thin metal) at the expense of longevity in many instances and areas... I've seen this firsthand as well as quite a lot on the forums / groups.

I'd take an educated guess that there is less than 1.95lbs difference between the '95-'06 KDX perimeter frame vs a '95-'02 KX125 frame, and I'd venture to say the '03-'05 KX125 frames aren't much lighter than the '95-'02, as the only major difference I'd think would be a very slight additional reduction in frame width.
'94 frames are similar to 95-98 KX, but had a reputation for cracking easily, so perhaps they're lighter? They were the last year KX of the KDX-style permanently welded on brake pedal pivot stud vs the 95+ larger diameter brake pedal pivot pin removable bolt with o-rings, a much better KX design and aluminum pedals as well to lighten things up. They also were revised in '95 to have more bracing around the shock mounting point.

One other thing, the '97-'98 and '99-'02 & last gen '03+ KX swingarms were significantly thicker box section height tubing, as well as a slight bit longer than the KDX and '95-'96 KX125 swingarms, so that in itself will add a bit of weight vs the KDX aluminum swingarm... And like I said, the longer larger diameter KX shocks will also add a bit of weight. There isn't any excess in the KDX shock, it's as minimalistic as they get and made of the same materials, just smaller than the MX and modern shocks....
Overall, this KDX220/'97 KX125 hybrid project should be a fun one that yields another amazing bike, and if I decide it's not different enough vs the KDX220 chassis with all the extensive mods I've done or am doing to it, I can seek out a '98-'02 or '03-'05+ KX125 engine to build a 134cc or 134cc woods ported build that'll drop 12lbs right away off the weight of a KDX hybrid.