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Author Topic: KX 125 L1 1999 Complete tuning  (Read 343 times)

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Offline MX3ME

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KX 125 L1 1999 Complete tuning
« on: July 16, 2020, 02:48:07 AM »
Hi guys.

I'm Eros and I'm Italian, I own a little dirtbike workshop and a race team near Milan and I am a two stroke addict since I'm 8 years old.

Back in the day, It was 1999, I fall in love with Torrontera's and Procircuit Kawy, so, i promise to myself to build a bike like that when i was grow up.
(Sorry for my horrible english skill, but I've learned to write by myself).

Three years ago i spot a relatively well used Kawy to my project, paid 1400 bucks, loocks pretty and works relatively well.




Unfortunately I've discovered that the bike looks amazing but has some critical engineering issue:
-the engine has a weird powerband, dead slow on low rpm, good hit on mid so I think "oh yes dude, it goes!", and no top, flat overrev that make useless to go on and need continuos shifting to keep the engine in the meat.
-clutch lever is relatively hard.
-front fork is weird, starts hard, then fall down for a little and after became really hard, smashing on the arms at every single bump.
-brakes were mushy and has no power.
-shock was decent when compared to the rest of the bike.
-rims are prone to crack on nipples hole.
-general bike quality is near to crap, footpegs have a terrible play, screws from tank pops out with the nut, triple clamps with no possibility to set the handlebar position (but on the same year 250 it is possible Whatta**ck???).

So i decided to rebuild entirely the bike to made it perfect in every aspect.






KX 98 to 02 engine are difficult to made fast, YZ or SX can have big improvement only with a couple of tweaks, kawy engine seems to refuse any kind of conventional tuning improvement such as porting, reeds exhaust or head machining.
I've modified my KX this way:

First I've create a mold of the transfer port (don't look to the piston, it isn't from kawy) to study where i can work, then i decided to leave it stock, except for the front scavenge port.
I have grinded it on crankcase side of about two mm on the perimeter to achieve more precision in reed control by the exhaust.





I've not grinded the other ports to prevent a lack of primary pressure, kawy transfers aren't perfect, but grinding material can cause the engine loss the bad low and the decent mid pull from stock configuration.

For build up more pressure I've put two plugs into the crankpin (made from a 7076 AL bar) and i switched the stock rod with a forged wossner rod.
I've tried to use many different piston on this bike, honda, KTM and even the old Husqvarna piston.
The only configuratio that was interesting is the KTM one but I've removed it before the ring being catch from a tranfer port, due of the different pin position.
So i bought a wossner piston for kawy and i made it flat by turning about 0,5 mm form dome.
I also machined the exhaust port, removing 1,5 mm on each side.
Because of the KIPS design i cannot made the exhaust port any higher so I've put 2 gasket instead of one under the cylinder, then i have turned the head down to match the right (0,9 mm) squish measure.
I've bolt on a KX 125 1993  reed valve with aktive reeds, a KX 250 PWK 38,5 (with powerjet and KTRICK) and a Messico Exhaust with a Bud silencer to let the engine breath properly.

Clutch, bearings, shift shaft and all the engine ruined parts was put on brand new from Partzilla.
125 Is the ultimate challenge for the rider and even for the technician...

Offline _X_

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Re: KX 125 L1 1999 Complete tuning
« Reply #1 on: July 16, 2020, 12:00:34 PM »
Firstly, welcome MX3ME!
 Very interesting procedure to create the power you desire. I am one for Pipe, silencer, reed valve and ride. I am interested in these Messico pipes you mention. You will find not many replies here sadly. I have a friend here in the states that followed the GP circuit in 1992 and hung around the Italian rider Giovanni Cavatorta as he tried to qualify, having that his father immigrate from Italy and speaking the language helped. Never did qualify, but made reserve a few times. he raced a national at Trentino. Thanks for sharing.   

Offline MX3ME

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Re: KX 125 L1 1999 Complete tuning
« Reply #2 on: July 16, 2020, 11:45:51 PM »
Thank you X

I Know that it can sound strange to work as hard to build up a serious powerband on a engine, but if you read the follow article or you ride a KX 125 model L1 you can discover what i mean.
The powerband of the stock bike is poor and particular, you must shift till death to keep the engine boiling and made speed.

https://motocrossactionmag.com/we-test-the-1999-kawasaki-kx250/

The 98-02 KX 125 engine was a cheap improvement made to try to revamp an old bottom end with few R&D dollars, it si not a surprise that the engine became so good when it was completely redesigned in 2003.
Here Pipes, Silencers and reeds can only make the enginge hard to ride, loosing the poor bottom pull and midrange without a significative gain on top.
Kawy engineers know about this problem and they try to made a distinctive powerband through years without any significative result.
In 00 they moved the ports around and they added a heavier flywheel to help torque and overrev. They only gain 1 Hp but the bike were still slow.
In 01 they removed the heavy flywheel, moved the ports (another time), modified the reed valve and manifold and replace the shorty PWK 36 with a more powerful TMX 36. The bike gain another 1 hp but, becoming a little fun to ride, but YZ and SX powerband of the same year are another story, even the RM in 2001 is faster than Kawy, only Honda have made worst than the green this year.
In 02 they also moved a little bit the porting, something changed but the bike remain globally the same.

Someone could say: "Why if making the bike fast is possible they didn't made it?".
This is an easy answer... Money... Because to transform a L series KX from an anhemic chainsaw engine to an Apollo rocket it needs serious modification to crankcase, cylinder and piston.
This mean new molds, new molds means a large amount of money.
Kawy wouldn't throw any R&D dollars for an old engine because they are working on the all new engine they present in 2003.
So this is the story.
I've seen that Messico pipes are not so much famous out of italy, it was designed from a techinician near florence that worked several times on world championship YZ with Rinaldi and became the official supplier for YRRD pipes and silencer in the mid of the 90's.
This pipe are developed to gain the maximum pull from every engine, they requires a skilled rider to keep it working well but they sounds amazing and they put on the table serious speed and torque at higher RPM, letting you to use big carbs without problem.
And they looks like "Hey, I am the most mad and skilled badass on this track!"  : ;D





After this explanation I'll show you how the bike finally looks, i have choosed the color pattern of Mike Brown's simple green Kawy.
-Full suspension work from poletti suspension, revalving, DLC, and a complete rebuild and spring sobstituion.
-Full Galfer Oversize brakes, new lines, new pumps and calipers.
-New SDG seat with custom seat cover.
-New excel rims with tusk spoke and nipples.
-New triple clamp machined from billet.
-New titanium footpegs
-Complete renthal final drive (12-48) With DID MXA520 gold chain.
-Renthal bar mounts with WRP America series 28 mm handlebar.
-Domino fast throttle with WRP reinforced throttle cable.
-Boyesen covers.
-NGK special plug cap for R7282-10 kart plug.
-All bolts and screw are titanium for structural parts and ergal for plastics and bodywork.
« Last Edit: July 17, 2020, 03:04:48 AM by MX3ME »
125 Is the ultimate challenge for the rider and even for the technician...

Offline _X_

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Re: KX 125 L1 1999 Complete tuning
« Reply #3 on: July 17, 2020, 03:05:43 AM »
Bravo MX3ME! Bravo! Bike and knowledge is top notch, would be an honor to ride with you. Unfortunately, there is a massive ocean between us lol. Maybe one day we ride.   

Offline MX3ME

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Re: KX 125 L1 1999 Complete tuning
« Reply #4 on: July 17, 2020, 03:11:53 AM »
Many many thanks, but I'm not a top technicia, I love my work and my sport and I put several sweat on my bikes tuning and set up, but I do also a lot of mistakes sometimes (for example when i have tried to put a longer rod into the RM  ::) ) anyway if you came to Italy and you come to Mantova it would be nice to ride togheter.

Ps: I made a Carbonara that could awaken the dead  ;D
125 Is the ultimate challenge for the rider and even for the technician...

Offline MX3ME

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Re: KX 125 L1 1999 Complete tuning
« Reply #5 on: July 17, 2020, 06:13:10 AM »
Some shots of bike details





Here a little video of bike after engine rebuild, it is lean on top, carb in this video was stock, but the exhaust sounds nicely  8)

https://www.facebook.com/Eros.lui/videos/10215808623000169/

with some tweaks added but still anhemic

https://www.youtube.com/watch?v=3I5fL0M0v0g&feature=youtu.be

A little video of the second evolution of the bike, Honda piston on it, still slow, but a lot faster from stock, track is Mantova last year, before i broke my wrist due of stuck throttle cable  >:(

https://www.youtube.com/watch?v=Y0Wok-3tvCQ&feature=youtu.be
125 Is the ultimate challenge for the rider and even for the technician...