History of the Kawasaki KX100 1994-2014 + Tuning tips, Flaws&Fixes /DirtBikeDudeZ

The History of the Kawasaki KX100 1994-2014
Engine tuning tips, Flaws&Fixes, Suspension tuning tips
SUBSCRIBE for more KX60 KX80 KX100 infos and tuning tips ;)
History:
The KX100 is a 2-stroke motocross bike made by Kawasaki.
The first real KX100 was introduced in 1994. Before that only the
KX80 big-wheel model was available.
The bike offers a good transition between the traditional 85cc
bikes and the 125cc bikes by having larger wheels (19inch front,
16inch rear, compared to 17/14 of normal 85´s).
It´s predecessor is the KX80 big-wheel, which is still sold under
the name "KX85-II". Longer travel suspension and larger bore
size are the main differences between these bikes which
otherwise are the same.
The KX100 can be raced in dedicated 100cc motocross classes,
or open minicycle classes, such as Supermini in Canada.
Which allows up to 150cc 4-strokes and 85cc-112cc 2-strokes
as of 2007. The KX100 can sometimes be raced in the 125cc
class. 100cc bikes are not very common.
1994-1997 KX100
Flaws: mismatched ports, soft forks, under carburetet
Fixes: port cylinder, stiffer springs and basevalve kit, 28mm carb
Best Value Mods: Engine: 28mm carb
Suspension: base valve kit
Engine:
The KX100 cylinder can be improved greatly. Kawasaki used the stock 80cc
cylinder casting and bored and plated it for a larger piston. The problem is,
they used a pipe designed for an 80cc engine, and the ports aren´t corrected
to suit the flow of a larger piston.One simple mod can be performed to the
cylinder for better throttle response. Drill two 6mm holes on each side of the
intake ports into the transfer ports. These are called Boyesen ports after the
prolific inventor. The KX80 allready has them. Also, use a file to widen each
exhaust port to a total of 27mm wide (measured with a thin plastic ruler
conformed to the bore). Set the height of the exhaust port 25mm from the
top of the cylinder. A simple bolt-on item that gives smoother power with
more top-end is a 28mm carb. Both Mikuni and Keihin have carb kits available.
A boost port can be added to the intake side of the piston; use a KX80 piston
as a model for duplication.
Hot Suspension Mods:
The big-wheel KX100, introduced to America in 1994, has
upside-down cartridge forks. The compression damping of these
forks can be greatly improved by installing the compression base
valve from the 1992 Yamaha YZ125. Pro Racing makes a tuned
aftermarket base valve for the KX big-wheel forks.
1998-2014 KX100
Flaws: sluggish powerband
Fixes: porting, bigger carb
Best Value Mods: Engine: porting, 28mm Flatslide Keihin PWK carb,
FMF pipe
Suspension: springs
Engine:
This latest generation of the KX100 featured a new exhaust valve system. That feature wasn´t well
received because it didn´t give significant performance gains. Plus the system was plagued with design
problems that included frequent breakage of the flapper part of the valve.
Cylinder Porting:
Since the 100 cylinder is just a bored out 82cc cylinder, the ports are too small for such a large piston.
Key areas like the transfer ports and exhaust outlet and bridge must be machined to let the gases flow through the cylinder. When i port a KX mini cylinder, i use an old exhaust pipe flange fitted to the exhaust outlet. This helps me cut the appropriate material out of the cylinder. the exhaust bridge can be narrowed to 2mm wide and the outer top corners of the port can be blended for better flow and less chance of ring scuffing. The exhaust port height can be raised to 25mm and the transfers to 35mm.
The rear transfer ports can also be widened 1,5mm towards the front transfers. The head doesn´t need any modifications unless you are building the engine for strictly low-end power.
Alternative Big Bores:
The Kx is a prime platform for a big bore because the crankshaft can be stroked easily and Wiseco makes piston kits 2mm larger than stock.
The maximum displacement possible from a KX100 is 121cc. RPM in Covina, California, offers bore and stroke engine mods for the KX. However, anytime the engine is modified for more displacement, the stress on the engine parts becomes significantly greater and the longevity compromised.
Aftermarket Carb:
The best choice of an aftermarket carb is the Keihin PWK 28mm Flatslide.
!!!KEEP ON BRAAAAPIN!!!
DirtBikeDudeZ

[@badboyjose71]

Good work

[@AdventureDaily]

Awesome video thanks for the information! My 2012 just blew up and I found a 98 for super cheap I'm just going to swap the engine and be done with it👍🏻

[@kainhall]

ive got an old 1974 kawi g5 100.... the kx 100 before 1994....same engine, same frame, same bike, different plastics.
its a rotary valve engine.... and im 180 pounds and 6 foot 5. gets my ass around just fine!
but this engine is a lot more street friendly... it is an enduro after all (the g5, not the kx 100)...but put it in first, wack open the go handle.... and stuff like this is totally possible.
i kinda want to find a differnet g5 or early kx100 with the rotary valve engines and just make one SCREAM. cut the rotary valve, mess with ports, figure out a better flow path for the carb.....go all out.
i love my g5.... just a handy little "run to the parts store" bike that KICKS ASS off road. it doesnt do it as fast or flashy as a CR 500... but it gets the job done!

[@kerm9807]

I have a chance of a kx100 1995
It has a black frame is this standard?
Are the wheels aluminium?

[@yaseenamin8056]

I have a 99 kx80 I’m thinking of swapping g cylinders but I need some solid proof that this will work but I think after this I’m going to buy a kx100 cylinder,head,and piston

[@DirtBikeDudeZ]

Yeah it fits, im doing the same swap

[@yaseenamin8056]

@@DirtBikeDudeZ thanks for the info very much appreciated!!

[@billjohn5957]

False i had a 1992 model kx 100

[@a.k.3811]

ik its 4 years later but that was more than likely a 80 big wheel or a Kawaski KE100 there's no possible wat to have the kx100 model before 1994