We answer five of the most frequently asked questions about KTM dirtbikes...
KTM dirtbikes – ORANGE questions
1. MINERAL OR SYNTHETIC
On my earlier model KTM it says I have to use mineral oil in the hydraulic clutch system but on my new one it says I have to use DOT 4 brake fluid. Can I just use DOT 4 in both bikes?
The earlier model Magura hydraulic clutch systems used rubber seals that could only handle mineral oil. If synthetic brake fluid is used in these systems it will cause the rubbers to fail and the clutch system to stop working.
The later model Brembo clutch systems use rubbers that can handle brake fluid so it is recommended that they be filled with DOT 4 brake fluid.
2. SHEAR FORCE
I have seen many KTMs that have torn the rear sprocket clean off the alloy hub. This has always turned me off owning one. Is this a fault with the hubs or something to do with chain adjustment?
KTM has beefed up its rear hubs in the last few years so we rarely see this issue crop up. It was caused by excessive chain tension. If the chain was too tight then, as the long-travel rear suspension compressed, it would tear the sprocket straight off the hub. The trick was to adjust the chain so that you could fit three fingers loosely in between the chain and swingarm at the back of the chainguide. The chain might look slightly on the loose side with the suspension at full extension but you wouldn’t destroy a hub.
I own a KTM and when I spin the rear wheel with the bike on a stand and look at the countershaft bolt holding my sprocket on, it appears to be off-centre, like the bolt or the countershaft is bent. Is this a problem?
This is actually quite common and scares a lot of people. More than likely, your countershaft is not bent and neither is your sprocket bolt.
On many of these bikes the threaded countershaft bolt hole was actually drilled and tapped slightly off-centre in the countershaft.
If you remove your chain and front sprocket and spin the countershaft using the kickstarter (with the bike in gear) you will more than likely notice the shaft is dead straight.
The offset bolt hole will cause absolutely no harm to the performance of your bike and is common to many KTMs.
4. OVERFLOW DRAMA
I have a KTM 450 EXC and it is always sucking coolant. Every time I go for a ride I notice once it has cooled down that the coolant level has dropped in the radiator and it takes nearly half a litre to fill it back up.
Once I fill it up and start the bike the coolant starts pouring out of the radiator overflow hose almost instantly. Do I have a water pump problem?
It is common for these bikes to do head gaskets and, instead of the coolant leaking into the cylinder or out over the motor, it only leaks enough for the piston to pressurise the cooling system. Every time the piston comes up, combustion pressure goes past the head gasket and into the water jacket, pressurising the system. Once the cooling system is over-pressurised, coolant is pumped out through the radiator overflow hose. The only fix is to replace the head gasket and torque the head correctly.
5. PEDAL ADJUSTMENT
I have a 2014 KTM and I’m trying to adjust the rear brake but whenever I adjust the pushrod that goes into the master cylinder all that happens is the rear wheel locks up.
I have only owned Japanese bikes previously and I never had a problem adjusting the rear brakes on them. What am I doing wrong?
The rear brake on the KTMs have a level adjuster on the brake pedal that Japanese bikes do not have, which is more than likely what you are doing wrong.
To adjust the height of a KTM brake pedal we adjust the height adjuster bolt underneath (on the bottom rear of the brake pedal) to get the desired height.
Once you have the desired pedal height you lock that height adjuster bolt up and then adjust the pedal free play by adjusting the bolt and locknut on the master cylinder pushrod. Never remove all the free play.
Always have 2-4mm at the pedal, at the very least, or the rear brake will lock up when the fluid heats up and expands.
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