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How To Run In A 2 Stroke Engine

First 5 tanks of fuel (running in) 25:1 mix ratio at low to moderate RPM.

GRC reverse water cooled engines check gearbox oil level before starting engine.

A115 and GPA115 engines do not require gearbox oil

  • Please use 25:1 fuel/oil mix, use a standard 2 stroke oil DO NOT USE FULLY SYNTHETIC OILS for the run in process because full synthetic oils may glaze the bore or fail to remove the fine metal fragments that occur during the run in of new engines. 
  • Fuel, only use 95 to 98 unleaded, DO NOT USE  91 unleaded fuel as it contains higher levels of Toluene which can swell or damage the small rubber parts inside carburettors and fuel taps. DO NOT USE high octane race fuels or octane boosting fuel additives during the run in process.
  • In a well ventilated area,run the bike engine on idle with the bike on a centre stand, let it idle for 5 minutes, then stop the engine. Let the engine cool down fully for 30 minutes. Once the bike engine has cooled, idle again for another 5 minutes, let engine cool for 30 minutes.
  • Continue this process until the first tank of fuel has been used.
  • Next tank of 25:1, ride the bike but with only enough revs to get the bike rolling slowly for 10 minutes, keep bike rolling at low rpm. Allow the bike to cool down fully before continuing run in. Check chain tension is good (about 2-3mm play at tightest point of lower chain in the middle of front and rear sprockets) Continue to ride at low RPM until the fuel tank runs empty.
  • Next tank of 25:1, ride the bike with low rpm and every now and then increase rpm slightly DO NOT GO TO FULL RPM, continue low to medium rpm for 1 full tank of gas. Let the bike cool down fully, check chain tension. (If the bike is stopped at any point, let the engine cool down before continuing the run in process.)
  • Next tank of 25:1, ride the bike low to medium rpm and take the bike to full rpm for about 3 seconds, return to low medium for a few minutes, increase to full rpm for few seconds, continue this process until tank is empty. Check chain tension.
  • Next tank of 25:1, carry out a good ride test, allow the engine to travel through its full rev range but do not stay at maximum rpm for more than 10 seconds at a time.

Check chain tension every 30 minutes of ride time (as high RPM will stretch the new chain until the chain is fully run in). Once the fuel tank is empty, let the bike engine cool down. Check engine base bolts are tight.

  • On the A115 engines, remove each cylinder base bolt and apply High Strength Loctite, then re tighten. Do the same for the two long carburettor bolts that are in behind the air filter plastic adapter.
  • On the GPA115 engines, remove each cylinder head bolt, apply High Strength Loctite and re tighten. ( Re-torqueing the head )

If the engine makes a squeaking sound while running, it is more than likely a compression leak from the base or head gasket, so do not forget to re torque the bolts.

  • After this process of run in, the engine may be operated at normal track riding RPM. Once a full track run has been completed on at least 1 tank of 25:1 mix, you may lean the mixture to 33:1.
  • 40:1 and 50:1 fuel mixes are not recommended, testing has shown if fuels are too lean, spark plugs can melt and or damage to the piston can result.

While running in a new engine, do not allow the engine to create excessive heat due to long idle times, heavy rider weights, hill climbs or terrain that will cause stress to your engine like sand, mud or any other surface that will slow the wheel speed down requiring the engine to work harder to maintain movement.

It is important to keep the engines RPM to a low or mid range usage during the running in process (first 5 tanks of fuel) to keep engine heat to a minimum.

You MUST NOT use fully synthetic oil for the running in process, this may cause the bore to glaze and can result in permanent engine damage

Recommended oil for running in:

  • MOTUL 510T 2 Stroke Oil
  • Castrol 2T non synthetic