Was there ever another 125 like the 1984 KX125?

Bonecrush wrote:

Wondering if there was ever another a 125 from the late 80's or 90's that had a powerband like the 1984 KX125 ? Torque and grunt right off the bottom and ripped all the way to the top ? I know the CR125 engines from the 90's were legendary, but my understanding is they were mid and top with almost no bottom. Did anyone else ever recreate that 1984 KX125 magic ? (Or did Kawasaki in a later year)

All of that with a non PV engine? I don't remember mine being that way, but that was a long time ago too. My 85 was way better.

I rebuilt an 85' KX and a 87' CR at the same time a few years ago. While the 85' was similar to the 84' and had a quick revving snappy powerband with a light flywheel, the 87' CR had a wider powerband up top and would rev out way further. On a fast track, I preferred the CR. On a tight track, the KX. While the KX was a good engine, it required you to shift more than the CR. Great engine for its time, but yeah, 125 engines have gotten better.

My 84 “Klemm Research” KX125 was Money ? everywhere in the motor department. Problem was the frame was a POS and kept breaking, I remember my Dad learning how to weld because of that bike. My 85 KX 125 was still my favorite 80’s model 125 even over the 86 and 87 Honda’s.

I agree, the 85 KX125 was awesome in the engine (and suspension) department! -Of course I was coming off a 1984 RM125 at that time! But I remember the power being just amazing...Ahhh, to be 21 again!!

In 84 I was riding an 84 WR125 Husky and doing some mx in local trail bike class. Tried out an 84 KX125 and remember thinking what a better woods motor it would have been.

My brother had a pair of 84’s, and a pair of 85’s (all Kaws). He said they were all great, but the 85 didn’t quite pull as hard as the 84. Said the 84 was easier to go fast on

oldmxracer wrote:

In 84 I was riding an 84 WR125 Husky and doing some mx in local trail bike class. Tried out an 84 KX125 and remember thinking what a better woods motor it would have been.

I dont get the whole 450 thing for woods, I rip on a 125.

I had '83, '84 and '85 KX-125's before moving on to KX-250's.

I realize anything is going to be subjective, especially when it comes to preferences, riding styles, etc.

That being said- I always loved my '85 KX-125 over the '84.

The '84 definitely might have had a little more low end grunt compared to the '85, but the all round spread of power was much better on the '85... at least in my opinion.

Technically, I'm not sure what actual changes and differences were made between the model years. I recall the '84 having a little more of a gap in the mid-range compared to the '85.
I think that the best way to describe it would be that they gave up just a little bit of torque from the '84 to the '85 and stuck it in the middle. This equated to a smoother and broader spread of power, and less of the harder "snap" that the '84 had when working its way from low to high.

I somehow managed to get my '85 really early- maybe like in August of 1984- which seemed pretty early in those days. I held onto my '84 throughout the year, and rode it only in a couple mud races- not only to spare my new '85 from getting ground up from the mud, but also because the '84 was more like a tractor in the mud with that low end.

Both were really great bikes, but my favorite was the '85.
In my 40+ years of riding and racing, the '85 KX-125 would make my top 3 favorite bikes that I've ever owned.

Some great responses here, it seems I'm definitely not alone for how I remember the 84. My brother got a new 85 KX125 (I was already away in the Navy) he also had an 84 and liked them both. No one has offered another year, make or model yet on this topic, so it seems that 84/85 KX125 engine was never duplicated. I get how modern 125's make a lot more horsepower, but I'm talking about 125 power delivery here. I realize if you ride a 125 "properly" your not supposed to need low end, but for us mere mortals, and the popularity of the 84/85 KX125 it sure seems like Kawasaki did something right those years.

They KX 125's had strong motors back in the day. If any bike to have that kind of power band I would say the 97 YZ 125, that bike had great low end and much more mid and top then the older 84-85 KX's. Yamaha's first few year case reed motors had very strong low and mid range motors but nothing much after that. Anyone know what kind of rear wheel horsepower the 125's in that era put out? I'm restoring a 82 RM125 and I think the RWHP on that bike was around 22-23 which is weak, the 87 CR125 was around 29-30 with plenty over rev. It seems most 125's up to now were around 35 with the new KTM's 37-38.

there are only subtle changes between early KX125 engines. The difference in the 84 from the 2 years before are a different CDI and minor porting. I have an 83 but I wish I put my efforts into a 84. The 84 is my favorite looking bike. Somewhere I have a Kawasaki Wrench Report for strengthening the frame of the 84 KX

MaxPower- I'd love that info on the frame if you have it, I'm about to take my 84 down to the frame. Thanks Greg

My memory fails me sometimes, but didn't the 84s come with crank bearings that had some kind of polymor structure that held the balls in place that would just disappear if you ran the wrong 2 stroke oil,?

Had a buddy that ran belray and had a motor knocking and split the cases. Not a trace of the ball holders anywhere, just free rolling balls on both sides. Dealer said they were getting reports of similar failures due to some chemical reaction with some lubricants.

I know the crank bearings went out of my 82 KX125 really fast using Bel-Ray. I was at a LL qualifier, Mike Roths mechanic told me I screwed up. It took less than 10hours to ruin the bottom end. I am racing a 85 KX125 now on Yamalube at 32:1 seems to be ok in it.

JustMX wrote:

My memory fails me sometimes, but didn't the 84s come with crank bearings that had some kind of polymor structure that held the balls in place that would just disappear if you ran the wrong 2 stroke oil,?

Had a buddy that ran belray and had a motor knocking and split the cases. Not a trace of the ball holders anywhere, just free rolling balls on both sides. Dealer said they were getting reports of similar failures due to some chemical reaction with some lubricants.

That was the 86 kx 125 where the Bearing Cages Melted....

I had one and absolutely loved it. Made me feel like a much better rider than I actually was.
The powerband and handling suited me very well.....I have great memories of that bike.
Pretty sure I got my first (and only) top 5 in the 125 Novice class with it.
Sold it to my brother in 86 , and unfortunately it got stolen a few months later.
I had an 87 for a short time also which was nice, but the 84 was one of my favorites.

Ivery been searching for it Bone Crush. It was on a vintage Facebook page. I saved it. I know I have it somewhere. I'm not giving up yet
Do you have a front fender brace?
If you are going for new plastic go for Nightmare plastic. Although it still takes some tweaking. When building my 83 I took it down to the frame. I remember thinking how frail the frame looked. Remembering every one who raced an 83 KX back in the day had a 83 KX125 with a cracked or repaired frame I welded gussets all over the swing arm pivot area and also had a metal skid plate welded on. Looking at the Kawasaki Wrench report for the 84 I see I should have strengthened the steering head area a little more.

MaxPower, if you could post a copy of the frame strengthening article it would be greatly appreciated.

I've had my 84 125 for a few years now, but its just been sitting in the garage waiting for my time to get it race ready again. It's a relatively low hour bike. I just took the cylinder off tonight and a bit heartbroken to see the exhaust port bridge cracked right through. was this a common problem with this model? I guess its repairable... just thought i was through spending money on this beauty, i guess not. Took me the last two years to find all the original plastic pieces (bar front plate) nos, and a nice nos Answer silencer. Suspension all rebuilt. I was getting pretty excited about hitting the track soon but have to fix the engine now... these old KX's really are a labour of love, i've been temped to abort this one a few times, but i still think its just one of the greatest looking bikes Kawi ever made... my head says park it, my heart says build it up and rip it!

wr74 send the cylinder to Millenium, they can fix it and replate it and it will come back better than new. They have saved at least 6 vintage/post vintage cylinders for me over the last 4-5 years.

I will post it .I still haven't located it. I know I have the bulletin
Dr Greg is absolutely right about them fixing the cylinder. I sent a totally trashed ebay cylinder to them with a 1/8" gouge the length of the bore. It came back way better than new. The early electrofusion was junk. The new plating looks too nice to use.

Got it!

MaxPower, you 'da man !! That is awesome info you were kind enough to search out and post for us all. I've been hunting for this bulletin to no avail for a long time. Thank you !

Had a 80,81,82and the 84. Those 80 and 81 where some real turds! The 82 much better and that 84 was great. Looked so modern and had very few issues with it. Worked at local Kawasaki dealership and had team green rider Richie Halstead riding one. One time at millville his bro Bobby was a no show with his bike and let him ride mine. He beat the late great Donny Schmidt on it. Oh good times!!!

JustMX wrote:

My memory fails me sometimes, but didn't the 84s come with crank bearings that had some kind of polymor structure that held the balls in place that would just disappear if you ran the wrong 2 stroke oil,?

Had a buddy that ran belray and had a motor knocking and split the cases. Not a trace of the ball holders anywhere, just free rolling balls on both sides. Dealer said they were getting reports of similar failures due to some chemical reaction with some lubricants.

kx93rfo wrote:

That was the 86 kx 125 where the Bearing Cages Melted....

Thats odd, I had 2 '86 models and they were solid.I ran nothing but K2R premix @ 32:1.

I heard from someone that used to beat me on a 1980 and 81 KX125 that if you advanced the timing abs cut the intake skirt of the piston that it really helped those motors. I think the only thing that could help those bikes was a strong tailwind

MaxPower- do you know if these same frame mods apply to the 1984 KX250 ? I just picked one up and have been reading they had frame cracking issues as well ?

Bonecrush wrote:

Wondering if there was ever another a 125 from the late 80's or 90's that had a powerband like the 1984 KX125 ? Torque and grunt right off the bottom and ripped all the way to the top ? I know the CR125 engines from the 90's were legendary, but my understanding is they were mid and top with almost no bottom. Did anyone else ever recreate that 1984 KX125 magic ? (Or did Kawasaki in a later year)

I recall the 84 kx125 would hit hard down low right off the bat, then fall flat just as you'd wish it would pull. The 86 n 87 cr125 had a way better engine it pulled everywhere, not to mention it was better at everything. Those 84 125 KXs ..i.saw a few guys break their frames.

DrGreg wrote:

MaxPower- do you know if these same frame mods apply to the 1984 KX250 ? I just picked one up and have been reading they had frame cracking issues as well ?

I have no idea Dr Greg. If the frame has the same basic design I can only assume similar gussets would help. More is better just be certain your bike will fit back together and you don add steel in the way of parts that bolt back on

MaxPower wrote:

Got it!

max, do you know thick the reinforcement peices are? also that yamaha seal, is that for both sides of the case. thanks