How to setup clutch and how to do regular Maintenance
The proper clutch is so important on all 50cc motocross race bikes that have the standard three
shoe clutch. Cobra King 50cc, Cobra CM50cc, Polini X1, X3 LEM R2, R3 or KTM50 Pro Jr, KTM 50
Pro Sr.All use the same type of clutch design. YES these bikes are very different, but the clutch
design and theory are all the same. Our specs, measurements and setups are used for our 50
liquid cooled 50cc engine.
However owners of other brands of bike may find some of these tips helpful.
Looking to put “maximum power to the ground” then, clutch adjusting procedures on your 50cc dirt bike
is maintenance and setup. In proper working order with clutch shoe engagement adjusted to optimum RPM
is your key to the best performance possible.
Is your bike purchased used? Is your bike over six months old?
Bikes with a clutch that's worn out or not adjusted correctly will make the bike feel slow,
sluggish, bogg or give it a slipping feel. If your bike is not brand new then think about replacing
the spring washers, clutch shoes and possibly the clutch basket with new parts. This will give you the
best performance possible because the clutch tolerances are very important to maintain. Also improperly
maintained clutch or worn clutch could confuse people in thinking that the need different size sprockets
carb jets or it may have bad ignition system but most of the time its due to a clutch not engaging correctly
maybe too-early or too-low in the working RPM range.
The three shoe clutch design seems to remain a mystery
to people who are afraid to maintain, clean, adjust or inspect them. With knowing a few basics these clutches
will not be so confusing or frustrating. The following is some basic advice received by a very experienced
racer dad that we would like to share with you…. If you have any tips or ideas please email us so we can post
them here for everyone to see. There are several things to consider when setting initial stack set for these KTM 3-shoe.
First and foremost: Skill and ability of the rider.
Second: Type of terrain, “motocross” hare scambles” “flat track” or recreational trail riding.
Third: How the bike is presently geared. You have to treat gearing and clutch set up
independently. Example: If you were to make a rear sprocket change to increase top end speed,
(Less teeth on rear sprocket) then you loose some bottom end power. Now with the clutch set up you
can change your power curve to compensate. Our advise is to buy a good dial/electronic caliper.
This is the most important tool in your toolbox. Next; for your initial stack setup go conservative.
I recommend the following as a base line setup for a beginner rider on flat terrain...
Legend for clutch washers: (HH) = head of clutch block bolt.
( = Bevel spring washer –notice direction.
/ = Flat washer in various thinknesses so all three of your stacks are within 0.003” of each other. Beginner setup is as follows. HH (( )) (( )) (( )) ( ) /
- add flat washer if needed to bring stack in tolerance. = 0.585” – 0.590”
Allow your child to ride the bike. Is he/she blipping throttle? If so allow child to ride bike longer
to see if child can adapt.
If your child is comfortable and riding more aggressive, this is my preferred stack...
HH (( )) (( )) (( )) ((( / = 0.610 This setup is more aggressive. The flat washer can be taken away or made
thinner or made thicker if needed for fine adjustment.
Again flat washer in stack up to adjust overall engagement speed.
Some basic pack thicknesses.
Motocross: anywhere from 0.590” – 0.670”
Hare Scrambles: anywhere from 0.590” – 0.640”
Recreational: anywhere from 0.580” – 0.610”
Remember change oil after every hard practice seesion and after every race. At motocross
races change between each moto. Use only Maxima MTL 75 wt Ultra light trans oil. Clean & inspect spring washers. The most important
advice to give is; Don't be afraid to experiment. Keep a notebook and record your findings. Some stacks work better then others
at different tracks, conditions, weather, sand, hard pack, mud, hills long starts etc… Got some ideas about KTM50 clutch in
o or set up you want to share with us? Please send us a
Email 50ccmoto@live.com or Call 239-566-9666