June: Proper Engine Break-In
It is important that when breaking your motor in that you do so under load. - "Under load" means that the engine can't free-wind RPM - The best way is to bolt the engine on your kart just as you would to race it. Be sure the kart is sitting on the ground. NEVER attempt to run the engine on a kart stand --this is a quick way to destroy your engine. Turn the engine (kart) completely upside down for a second just prior to adding fuel and starting. This helps get oil to the top end of the engine before startup.
Be sure that the piston is at top dead center (that's where the PTO shaft keyway is at 12 o'clock straight up.) Turning the engine upside down now allows the oil to coat the lower end of cylinder walls, piston, rod and crank jouirnals as well as the top end parts like springs, valves, and valve guides. Use alcohol fuel as usual and fire it off. Let the motor idle for 2-3 minutes to gain some temperature. Do NOT use a hot (high heat range) plug to gain temperature quickly.
Keep the motor running - Don't let it stall. If it does, quickly turn the engine over two complete revolutions by hand and then refire. When engine is about 200 degrees and increasing, start driving the kart in a smooth large circle keeping steady RPM under 3500, always keeping the engine under moderate load. Be sure to use an old clutch (the old shoe style GE series Noram clutches are perfect for this use.) You can also use a large clutch gear to reduce the final gear ratio so to help keep engine rpms down. Run the engine for ten minutes in this manner, then take a couple cool down laps, just coasting.
After a couple of cool down laps, bring the kart in. Shut off the motor. Hand turn the crank over two revolutions and stop on the compression stroke at TDC; cap the exhaust off with a tennis ball, duct tape or whatever you choose - This allows the enigne to cool down slowly so as not to crack or warp valve stems, guides, etc. Turning the crank over to TDC also allows the valve springs to relax at full length rather than cool down while they are compressed. This will retain good spring tension which results in increased spring life. Now it is very important to drain all oil while the engine is still good and warm. There is a magnetic drain plug in the motor so the magnet picks up any metallic particles floating around or settling in the oil. Clean off the end of the magnetic drain plug every time you drain oil.
Re-torque bolts - New motors tend to shake loose any improperly tightened bolt as well as some that were just fine. Especially check carb-to-tank as they are affected by fuel swelling the gasket; and carb-to-block, as they loosen with vibration. Do NOT overtighten. We generally paint a stripe of oil based paint to bolt heads that typically come loose. You can simply check that the paint stripe matches up rather than recheck torque each time you run the engine. Due to improved gasket technology, head bolts usually do not lose torque. Do NOT re-torque hot. It is very important to do this after the motor has cooled. I generally check the spark plug for good combustion only after the engine has ben completely broken in and is race ready. Check for lean versus rich condition, etc., but replace plug with another quickly so that cool air doesn't rush in on top of the piston.
Refill crankcase with remaining 16 ounces of break-in oil. Refire engine, and repeat previous ten-minute break-in procedure.
As temperature increases start using more throttle coming off of turns and more or less coasting down straights. After just a few laps your engine should be to 360 or greater temperature; now go full throttle off the corners - really lugging the engine down and coasting with NO throttle down straights. With each lap, increase full throttle "on" time until you are nearly up to race speeds and braking. Take one or two more laps just coasting at moderate speed to cool the motor some - If temeprature becomes a problem, keep richening the carb adjustment to keep temps below 390 degrees for beak-in. Try to keep temperature between 385 and 400 degrees optimal. (This is generally the temp we race also.)
Drain alcohol and run the engine on gas for at least two minutes to clean alcohol out so carb pick-up tubes will not clog. Drain oil, and re-check / re-torque bolts if necessary. After all oil is drained, I like to slosh some fresh oil around in the crankcase and drain it as well. This helps get rid of any additional metal particles which did not drain with the hot used oil. Then put in your 14 ounces of Cool Power (Green Synthetic) or your favorite brand of oil. By putting it in NOW, you won't forget it. If you have any questions or concerns on the proper oil or amount, please contact us directly or consult our additional oil technical page found on this website.
This entire break-in oprocedure will take around 30 minutes total, so be sure to allow yourself sufficient time to break-in your engine as instructed.
THIS IS NOT SOMETHING TO BE DONE ON RACEDAY.
Proper engine break-in is essential for increased performance and durability.
bcarlson@CarlsonMotorsports.com