Two-stroke KTM motorcycles have a bleed screw on the cylinder head. This is to bleed the air from the cylinder and cylinder head so that the coolant will circulate through the engine correctly and disperse the heat from every part of the engine. If this is not done or is not done correctly then it can lead to serious engine failure. This is our tip on how to Here’s how to bleed a KTM two-stroke coolant system.

#1 CHECK WATER PUMP DRAIN (no photo?)

Firstly you need to make sure the drain bolt in the water pump is tight. This is the bolt at the bottom of the water pump hosing that is fitted with a copper washer.

#2 LITTLE BLEEDER

Then you will need to locate the bleed screw located in the top rear of the cylinder head. Once you locate this bleed screw you will need to crack it loose.

#3 TOP UP COOLANT

Remove the radiator cap and then fill the cooling system with coolant until the system is full. Take note that the system is completely full.

#4 MAKE BUBBLES

Now using your fingers, loosen the bleed screw in the cylinder head until coolant starts to bubble up from the threads. Do not completely remove the screw as coolant will spurt out.

#5 NO MORE BUBBLES

Once coolant starts to bubble out of the thread on the bleed screw. Tighten the bleed screw back up and then take note that the coolant level has dropped.

#6 TURN IT OVER

Top the coolant back up and then wind the engine over by hand a few times to circulate some coolant so that any trapped bubbles are worked out.

#7 FINAL FILL

Then top up any fluid if needed and fit the radiator cap back into position.

#8 KEEP IT CLEAN

Lastly clean up any spilt coolant with a clean rag.

DO’S

  • Use new coolant.
  • Replace any copper washers if damaged.
  • Remember to tighten the drain screw and bleed screw.

DON’TS

  • Over tighten the drain screw or bleed screw.
  • Reuse any old coolant.
  • Leave spilt coolant all over the engine.

TOOLS:

Clean rags, spanners, torx bit, fresh coolant.

WARNING:

If your coolant system is not bleed correctly then air can stay trapped in the coolant system.

What happens if air gets stuck in the cooling system?

If air gets trapped in the cooling system then it can do a few things. Firstly it can stop the coolant from circulating and cooling the engine correctly. Another thing it can do is cause an air bubble in the cylinder or cylinder head which will not be cooled correctly. This can cause a hot spot which can cause the piston to grab the cylinder wall in this area leading to engine failure.

 WORDS & PHOTOS | MAT BOYD