Cycle Improvements

KTM Tech

Bought a KTM Motorcycle in the crate? Check out our PDI list before you ride.

Below is a list of our recommended modifications (mods) and tips for various models. Scroll down to find yours.

50CC Air-Cooled Minis
MOTOR
1998 to 2000
Under racing conditions the crankshafts can spread at the crankpin and go out of true - the fix is to have the crank trued and then tig welded on both sides of the crankpin. The centrifugal clutch can fail if you do not keep an eye on the 2 links and springs between the inner rotor and shoes. The links look like a chain master link and the clip can spread and fall off.

50CC Liquid-Cooled Minis
MOTOR
If you want to increase the bottom end power and throttle response on the 2003 50 LC SR, we recommend the following. We carry all the parts in stock:

pilot jet - #55 (48 stock) - part #45131007055
carb slide - #50 (60 stock) - part #9475-50
fuel screw - 3.0 turns out
stock needle - 3rd clip from the top
stock main - #85

2001
Some of these have incorrectly installed waterpump o-rings (pinched) that cause the cover to leak. We have replaced this with the gasket used on the 2002 model.

2001 to 2003
Engine Mods - We have developed a mono-petal carbon fibre reed to replace the stock bi-petal reed. This improves bottom end response with added top end as well. The mod involves removing the centre bridge of the reed cage for increased air flow and reduced turbulence. Part #MP-113LT-SPECIAL.

The waterpump bearings have to be watched closely as they do not run in an oil bath. Keep a eye on these a replace with a quality rubber-sealed bearing (2RS) when suspect. If you don't, the pump will seize up and destroy the shaft. Keeping the cover sealed and free of dirt and water will also extend the life of these bearings. The slot at the end of the water pump shaft is also prone to wear and should be checked every 30 hours. We use a moly-based grease on this, which helps longevity.

CLUTCHES
All 2002 to 2003 50CC juniors and seniors with the stock three-shoe clutches are often shimmed too tight as far as end float goes right from new. This can cause the engine to bog when warm. We recommend .007"-.010" end play. This can be changed with different shims, which we have in stock.

Clutch engagement for stock motors should be setup for this RPM range:

Junior models: 4,000 to 4500 rpm.
Senior models: 8,500 to 9,000 rpm.

This is set with the flat preload washers. One .5mm washer is equal to approx. 500 higher engagement speed. Overall stack height of the total washer stack should be .640" to .680" with the lower number usually better for lighter rides and visa versa.

SUSPENSION
All models that come with the WP shock:
We have a revalve modification that includes a remote reservoir that has adjustable compression dampening. This kit turns your stock emulsion unit into a decarbon type shock like the big bikes. Kit comes complete with a mount for the reservoir. Less fade and much better action. Part # MP-RRES-COMPADJ.

Rear shock sag on the Junior LC models should be 45mm and the Senior LC should be set at 50mm. This should require the shock spring preload be in the range of 5mm to 15mm. If it is outside this, then a lighter or heavier spring may be required.

The stock rear shock spring is good for a rider weight of 60 to 80lbs. If your rider is lighter than that, we recommend the 4.0kg spring part #WP-SW93010167. You should have 50mm of rider sag when the spring is preloaded 3mm to 7mm.

Common To All Minis
CLUTCHES
Clutch Theory and Setup

The 3-shoe clutch operates on the following principals:

Clutch Speed Engagement is determined by the following factors:

weight of the clutch shoes (which can vary shoe to shoe)
distance (clearance) between the clutch shoes and the drum
preload of the dished washers (initial force required to get the shoes to move)

Clutch hookup or engagement (fast or slow)
Spring rate of the dished washers, which is determined by how they are stacked. Washers stacked like this: )) have a heavier spring rate than washers that are stacked like this: () . A heavier spring rate will cause the clutch to smoother and take a longer period of time to totally lock up. This can be an advantage were track conditions and traction are poor. A lighter spring rate will allow the clutch to come in hard and fast and can be used effectively if the riders is good and traction ideal.

CHASSIS
We also have quick turn throttles in stock for the 2001-2003 50 air and liquid cooled bikes. This reduces the amount of turn required to open the throttle fully. Our throttle kit comes ready to bolt on with the only modification being to narrow the cable end slightly with a file. Part #EP-1005.

The front chain guide that goes around the swingarm on the 2003 models does not sit parallel to the chain and needs to be fixed. Remove the guide and on the backside of the mount change the angle so that the very front of the guard is moved over to the right when you look at it sitting on the bike.

The swingarm bolt on these models is too short as far as the non-threaded length goes from stock. This means that the threaded portion wears away at the frame, which eventually can cause the bolt to loosen and break. We sell a heavy duty grade. 12.89 bolt that is the correct length. One of part #SN366-911 and 1 of #SN657-239.

The 2001 to 2002 use a very poor quality steering bearing head set that wears out quickly and prone to cracking. You can use the bearing set out of the 2003 model or better yet we sell a heavy duty kit that eliminates any further problems. Part # MP-140-2035.

The 2002 to 2003 models came with a banana-shaped chain slider at the front countershaft sprocket instead of a chain roller. This slider needs a hole drilled through it and a nylon zip tie put through this hole and around the chain guard. This prevents the slider from being pushed from out and over the locating tab on the cover, which secures it in place. The slider is then free to rest on the bottom of the carburetor bowl, which it then will promptly wear a hole through.

Watch the chain adjustment as these are different from the bigger bikes as the chain gets looser as the suspension compresses.

SUSPENSION
To make a dramatic improvement in the front forks, we recommend the following. This will improve action and bottoming resistance while also improving the rebound dampening which will improve turning.

Install the correct fork springs - call us (.20kg stock springs are good for 50lb rider wt) part #342822 or 342824. Install an emulator in the left fork (compression side). Use 5 turns of preload on the emulator spring. Set oil height in both forks to 110mm from the top of the tube with fork compressed and springs out using 15wt fork oil.

Fork oil height for non-modified stock forks on all 50 models should be 110mm from the top of the fork tube with the springs removed and the fork collapsed.

65SX Models
MOTOR
We recommend the following jetting changes:

main - 220 (stock is 200) part #4/042-220
pilot - 35.0 part #M28-1001-35

This gives the bike better throttle response off the bottom and improved upper rpm hp.

We have aluminum plugs to replace the glass sight lens on the side of the engine.

The 2003 model has a poor gas cap design which can cause a problem with venting of the tank. This is responsible for the motor dying and bogging that some people have experienced with this model. Use the gas cap off of the big bikes. Part #KMP59007008044.

We recommend running 400cc of gearbox oil in all 65 models instead of the 300cc called for. The extra oil helps with clutch longevity and fade. See below for specific clutch details.

The front countershaft sprockets on 2002 and 2003 models are on backwards right from the factory. The correct way is as follows - sprocket flange faces out away from motor against the circlip, which retains it.

CLUTCH
1999 to 2001
If you're having a problem with the clutch dragging and the rider doesn't have really short fingers, you can put on a clutch perch/lever assembly from a YZ80 Yamaha. This allows the clutch to disengage better.

We recommend running 400cc of gearbox oil in all 65 models instead of the 300cc called for. The extra oil helps with clutch longevity and fade. If you are burning out clutches more frequently than you should, note the following: We have found that some riders with small hands have the tendency to ride with the clutch lever pulled partially in all the time (disengaged). We sell a modified stock lever which brings the lever in closer to the handlebar, eliminating this problem.

SUSPENSION
We can revalve the rear shock with MX-Tech valving for improved action and bottoming resistance.

We have an awesome MX-Tech setup for the front fork on the 2002 and 2003 models. This is an extensive modification, which turns you old style fixed orifice fork into a fully functional cartridge fork with midvalve just like the big bikes. It generally requires a lighter spring rate for most rider under 100 lbs. We are the only people to be doing something with these forks that make a substantial improvement in action and control. Call for pricing!

Rear shock sag on the 65sx should be 85 to 90mm. This should require the shock spring preload be in the range of 5mm to 15mm. If it is outside this, then a lighter or heavier spring may be required.

125SX Models
Watch for carbon build-up on the front of the exhaust valve as this can cause the powervalve to stick and in some cases will result in a squeak when revving the engine. The best motor mod (years 2000 to 2002 only) is to have the head modified. When using 104 octane race gas you can run .038" squish clearance with a decrease in combustion chamber volume to 8.6cc. The 2001 and 2002 125SX have a bottom/midrange biased-type cyl. head configuration. If you want better overrev you can modify the head to be like the 2000 model. Both Doma and Pro circuit pipes work well on this model as they help the throttle response in the mid with a slight increase in overrex horsepower.

The cyl. Head stays are prone to break on this model under hard usage such as Supercross. We have a stainless steel head stay that rectifies this. Part #EP1002.

We have Vortex ignitions in stock and have achieved good power gains in the upper midrange and top end overrev with an ignition map we have developed on our Dyno. These ignitions allow you to program two different curves which can be switched with the flick of a button. Please call for details. Part # VT-125SX.

The pipe sometimes cracks on this model starting usually at the first mounting tab. Check to make sure that the pipe is not mounted under tension. Also be careful if you have crashed on the pipe because it can bend in and rub on the rear shock spring. We have a mount for these that fixes both these problems. If your exhaust is rubbing against your shock spring, we have an aluminum exhaust mount which will solve that. A tab needs to be welded to your sub-frame. Part #TBA.

The stock engine reeds last usually about 40 hours before they start to fray as some of these engines are real revvers. We have found the Carbon Tech brand of reeds to offer good longevity and performance. A complete V-force reed valve along with jetting also gives good power gains on this model.

The clutch side gearbox drain screw will easily strip if overtightened as the case is very thin there.

This model uses 4 aluminum clutch plates which can wear rather quickly - keeping an eye on them will help to keep the clutch in good shape. For better durability you can replace them with 4 steel plates like the 2 already in there.

Jetting needs to be changed to this if you're at an elevation of approx. 1000 feet (years 2000 and 2001).

2000
Optional needle in clip 2 / stock main / up 1 size pilot jet and air screw at 1 turn out.

2001
Optional needle in clip 2 air screw at 1 turn out.

200 Models
Some of year 2000 models have a problem with the shift return spring located on the shift shaft disengaging from the tabs that hold the ends apart. The fix is to remove the shift shaft by taking off the big clutch cover and clutch basket. You need to remove this spring and bend the ends of the springs toward the tabs that hold it apart.

MOTOR
Jetting recommendations as follows:

pilot - #40
air screw 1.5 turns out
slide 7.0
needle R1468D, clip, 2nd from the top

These models respond strongly to a head mod for increased bottom end power. We change the squish, compression ratio and combustion chamber shape. Less fuel octane sensitive and nicer power.

2003 200 SX
Want the ultimate? Our 2mm over kit with porting, head mods, ignition timing and jetting setup gives you 250CC top end power with unbelievable bottom and midrange. Depress your buddies all day with this setup. Can be setup for pump or race gas. Phone for details.

250 Models
MOTOR
1999 and 2000
Head modification - reduce compression 1/2 point and squish clearance to .050" with a squish angle 1.5 degrees more than the piston dome angle. This along with welding up the exhaust port floor and increasing the exhaust port width below the transfers helps boost overall power considerably - best bang for the dollar. A Boyesen Rad valve helps with response and top end but needs to have the main dropped approx. 5 sizes to correct jetting. The best pipes we have found is the Doma or the FMF SST.

300/380 Models
MOTOR
2000 and 2001 - If you're not happy with the low end carburation try an R1366n carb needle. This along with main, pilot jet and sometimes a slide change is usually what we end up using when setting up the carburation on these models using our dyno. To improve low speed running on these bike they really need a head modification. The stock head has a very low maximum squish velocity and needs the squish clearance tightened up - you will find this along with the jetting is the best bang for the dollar.
We have noticed that the lower rad hose that links the two radiators and curves around the front of the cylinder head is sometimes pushed on the rad too far. This can cause the hose to come into contact with the cylinder head nuts. Thus rubbing the hose through and causing premature hose failure. Loosen the clamps and slide the hose down on the spigots. This will cause the hose to bow away from the cylinder head stopping it from wearing.

400 & 520 4-Stroke Models
MOTOR
2000 to 2002 400 SX
We recommend this jetting:

main - #168 - Part #WCKHH168
pilot - #45 - Part #WCKRPJ-45
fuel screw - 1¼ turns out
needle - OCEMN on clip 4. Part #MP-OCEMN
accelerator pump -adjust to 1-second duration

2000 to 2002 400 EXC
We recommend this jetting:

main - #162 - Part #WCKHH162
pilot - #42 - Part #WCKRPJ-42
fuel screw - 1¼ turns out
needle - OCEMN on clip 4. Part #MP-OCEMN
accelerator pump -adjust to 2-second duration

2000 to 2002 400 SX and EXC
We have a big bore kit which turns the 400 into a 450cc. It includes a 95mm bore piston, all gaskets and 95mm plated cylinder and is definitely a huge power gain (within 2 Hp of a 520). Combine this with a pipe and ignition and watch out. Part #EP1004

4-stroke electric start
Did you buy a KTM E-start for your 4-stroke SX, and find out the battery does not recharge? This is because a voltage regulator/rectifier needs to be wired into the stator wiring harness. We have a inexpensive regulator available. Part #MV001-15416 which includes wiring instructions.

CHASSIS
We mount the throttle assemblies so that the throttle cables exit from underneath the handlebar, as this location for the cables is much less prone to crash damage.

250 / 450 / 525 4-Stroke Models
MOTOR
2003
The 450 EXC is jetted very lean from the manufacturer. The following will greatly improve all-round performance. We recommend:

main - #152 - Part #WCKHH152
pilot - #48 - Part #WCKPJ-48
fuel screw - 1¼ turns out
needle - OCEMN, needle clip 4. Part #MP-OCEMN
accelerator pump - 1-second duration

The 525EXC is jetted very lean from the manufacturer. The following will greatly improve all round performance. We recommend:

main - #155 - Part #WCKHH155
pilot - #45 - Part #WCKPJ-45
fuel screw - 1¼ turns out
needle - OCEMP, needle clip 4. Part #MP-OCEMP
accelerator pump - 1-second duration

CHASSIS
We mount the throttle assemblies so that the throttle cables exit from underneath the handlebar, as this location for the cables is much less prone to crash damage.

NOTE: ALL ABOVE CARBURETOR JETTING SPECS ARE BASED ON APPROX.. 1000 FEET ELEVATION, HUMIDITY OF 50% AND 65 TO 80 DEGREE F TEMPERATURES.

Common To All Models Except Minis (see above for information on Minis)
Early 2000 models came with too short thread on the front axles and therefore it is easy to strip the aluminum nut. There is a special nut available to allow for more thread engagement. Later models come with a longer axle.

We have found that most models have 1 rate heavier fork springs stock then what is listed in the manual. Bottom line is don't buy a heavier spring unless you check your stock ones first. We can rate check them for you

On all bikes that we have checked it appears that the fork oil level is lower than the recommended stock oil level. This allows the fork to blow through the travel and bottom easier.

On early 2000 models the hydro stop/spring spacer in the front forks get damaged when the fork bottoms and this debris ends up in the valve stack. The hydro stop needs to be replaced with the updated unit and the valve stack disassembled and cleaned. These forks also need to have the valve stack retaining nuts loctited as well as the chrome fork tube where is threads in to the lower axle mount. This must be done as it is possible that these pieces can fall off with bad results.

The upper right subframe allen bolt is prone to loosen because of the proximity to the upper shock mount - blue loctite from new.

If you are rebuilding your wheels, please note the following: Front rim offset measured from the disc rotor surface is 25mm and rear is 35mm. The spoke nipples should be torqued to 50 inch-lbs.

PDS shock bearings
For maintenance of the bottom and top bearings we have found the following to be best - for motocross grease the seals only for the bottom - for muddy enduro use grease both the bearing and seals(use belray moly antiseize or equivalent) - grease the top bearing for all use.

Brake Calipers
Watch the pad guide pin as this will get a divot worn into it which will not allow the pad to move freely. You can increase its use by rotating it 180 degrees to an unworn spot. As well, we like to safety wire that pin instead of using the stock clip as we have seen these fall out. Check the sliding pins for grease as the rubber boots can let water and dirt in causing corrosion. If the rear brake is too sensitive try using EBC FA208R or FA208X pads. For the front, we recommend EBC MXS181 as they provide the best stopping power.

Clutch Master Cylinder
Keep the area behind the piston dust boot clean as dirt entering here can damage the nickel plating inside the bore causing the piston rubber seal to become damaged and leak. You then have 2 options - replace the cylinder or glass bead out the nickel plating and replace the piston assembly.

All models with hydraulic clutches may use regular 5wt fork oil.

If you want to make a dramatic improvement in your suspension contact us as Mx-Tech has THE setup for the forks and shock. The difference is dramatic!

Be careful if you have removed the caps on your front forks! When reinstalling you need to make sure that you turn the black hydro stop all the way down on the cartridge BEFORE you thread on the fork cap. If you do not do this there is a good possibility that the cap won't bottom on the cartridge rod first. What will then happen is you will have a problem with your rebound adjuster or you might find the adjuster just spins and does nothing.

If you have drained the coolant you must bleed the air at the bleed bolts (if equipped) and on the right radiator. Trust me, if you don't you'll be sorry, as you will have air in the system causing the engine to overheat.

To sharpen and improve the cornering on all models equipped with 20mm triple clamps, switch to the 18mm offset triple clamps. The bike cornering is then dramatically improved and the bike will carve a inside line like never before.

Fork Oil Level Adjustment
To set the oil level correctly there are two ways. Use the KTM specification and adjust level as follows. A: fill the fork to the very top of the outer tube.. B: pump the inner cartridge rod up and down to displace all air bubbles. C: Refill fork to the very top again and let the fork stand for 15 minutes if possible to let any air rise to the surface. D: use a fork oil suction tool to pull oil out to the level specified in your KTM manual.

The other way is to A: fill the fork with oil to within 1 inch of the top. B: pump the cartridge rod up and down to displace any air bubbles. C: refill the fork to 1 inch from the top and pull the outer tube (grey fork tube) up until it stops then back down D: set the oil level to the KTM specification as in method 1 less 40mm (e.g. if book spec is 140mm then you would use 100mm. The reason these methods are different is because the first method allows oil to stay between the inner and outer tubes. The second method pulls the oil from the inner tube to the outer tube therefore giving you a higher oil level (smaller number).

Rebuilding the PDS Rear Shock
To properly rebuild and bleed the air out of the PDS shock, you need to use a very expensive pressure bleed pump which very few dealers have invested in. However, we have invested in one to give you a factory quality rebuild - Don't accept anything less!

1999 50mm Forks
To help keep the fork seals from leaking you can use the 49mm Suzuki RM dust seals (results in some increased friction but worth it) or we have had good success with those Acerbis neoprene fork cover.

Lowering
We can professionally lower any model that has rebuildable suspension components to get your feet on the ground for those smaller riders without any negative effects on handling or suspension. The maximum we can lower effectively is 2¼'. This mod can be changed relatively easily back to stock height anytime in the future. Call for details

Adjusting Spoke Tension
*It is very important to only turn your nipples a half of a revolution, or two flats at a time on a newly laced wheel. If you find yourself having to turn more than a half of a turn go to the next spoke in the pattern, and gradually bring the nipples up to torque by working the pattern. Once you have all your spokes close to the torque range this will no longer be necessary. If you turn the nipple more than 180 degrees to bring it up to torque you will pull the offset of the wheel off to one side or the other.
1. Start at the spoke next to the rim lock. Call it spoke #1
2. Back off spoke #1 until it turns freely, then tighten until spoke torque wrench clicks. Go to spoke #4 - repeat step #2. It will come from the other side of the wheel.
3. Go to spoke #7 - repeat step #2.
4. Go to spoke #10 - repeat step #2.
5. Continue around the wheel torquing every third spoke, until coming back to spoke #1 (on a 36-spoke wheel). Move to spoke #2 and repeat step #2.
6. Go to spoke #5, then #8, then #11, continuing this pattern all the way back to spoke #2.
7. Move to #3 and use the same procedure on spokes #6, #9, and #12 and so on around the wheel.
8. It will take 3 revolutions of the wheel to complete the torquing process. You will torque 12 spokes per revolution.

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