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Installation Instructions

Your cylinder has been sized to extract its maximum potential. Because it has been fitted with close tolerances, a very important break in procedure is required. This is critical to increase performance without sacrificing reliability. Follow these guidelines closely and use the checklist to ensure that break in is completed in full.

1) After receiving your cylinder from CT, inspect it for any freight damage, if there are any questions contact CT immediately.

2) With dish soap and hot water wash your cylinder and piston only , scrub the cylinder bore with a paper towel until the towel remains clean. Dry the parts immediately and spray the cylinder bore with a liberal amount of WD-40, use a dry paper towel to spread the oil evenly throughout the cylinder.

3) CT recommend that you install new reeds and a new wrist pin bearing at this time, don’t leave anything to chance, if a part is possibly worn out then replace it now. If you have a Suzuki LT250 or 500 always change the wrist pin thrust washers, they have a history of breaking and can do major damage to your engine.

4) Put a couple of drops of 2 stroke oil on the wrist pin and pin bearing and install the piston. The arrow on the piston crown faces the exhaust port. If there is no arrow, the ring locating pins will face the intake port. Double check that the circlips are firmly seated in their grooves. Install the piston rings with the numbers up. The numbers are located at the ring end gap, be sure the ring end gaps are aligned with their respective anti-rotation pins.

5) Assemble the cylinder with new gaskets, do not use any type of gasket sealer. Do not put any more oil on the piston or cylinder, the WD-40 left in the bore is enough lubricant. Compress the rings with one hand as you slide the cylinder down onto the piston, look through the intake window to check the alignment of the ring end gaps over the pins, adjust the rings now with a small screwdriver as necessary. If the ring end gaps are not centered over the pins you may break the rings if you force the cylinder down, take your time. Torque the base nuts to the factory specs, install the head, torque the nuts to the factory specs.

6) Install the intake and exhaust systems with new gaskets, we suggest using orange high temp silicone on the exhaust flange. Install the water hoses and fill the cooling system with glycol based coolant mixed 50/50 with distilled water.

7) Install a NGK spark plug of the exact type recommended by the factory.

8) Install a new Dura-Blue air filter for maximum engine life.

9) Richen the jetting in the carburetor, up two sizes on the main jet and one clip position on the needle.

10) CT cylinder kits are set up for 100 octane race gas, fill your tank accordingly. A mixture of 50/50- 110 octane racing gas and 92 octane pump gas will generally be fine for all CT engine kits unless other arrangements were made.

11) If you received a complete engine from CT it was shipped with no oil, check your gearbox or crankcase and fill it as necessary. 

Break In Procedures

1) Start your engine and let idle occasionally blipping the throttle for four to five minutes. Allow the engine to cool completely. Repeat this "heat cycle" process four more times.

2) Warm up the engine again and ride the bike for five to seven minutes at a very easy pace, vary the rpm, don’t ride at one speed. Don’t ride at more than 1/3 throttle or more than 1/3 rpm. Let the engine cool down completely and repeat the initial break in ride. Let the engine cool down.

3) Check the base nuts and head nuts for proper torque, check the coolant level and add coolant as necessary.

4) Ride the bike for five to ten minutes at a moderate pace, vary the rpm, don’t ride at more than 3/4 throttle or more than 3/4 rpm. Let the engine cool completely and repeat this secondary break in twice more.

5) Replace the spark plug with a new one. Ride the bike for five to eight minutes at a moderate pace, vary the rpm and shift up and down the gears. Once the engine is up to operating temperature you can make a jetting pass. Start in second gear and ride at full throttle through fourth gear, fully revving out fourth gear. With the throttle wide open in fourth hold the kill button down, pull in the clutch and stop. This is called a "plug chop"

6) Read the spark plug. With a pocket flashlight and a magnifying glass look at the porcelain part of the plug only, as you view the plug from the center electrode look down the length of the porcelain to its base, at this point there should be a dark chocolate colored smoke ring. There was not sufficient time to thoroughly color the whole plug, so the nose of the insulator may still be white, as long as there is a visible dark ring at the base everything is OK. Remember we want break in jetting so the plug should read rich/dark. Richen the jetting as necessary. If your having a hard time reading the spark plug, after the jet pass put the plug in a vice and hacksaw around the plug at the washer. Break the threads off with vise-grips, and the porcelain will be easy to read.

7) Complete the break in by riding at an aggressive pace for fifteen minutes, vary the rpm and donít cruise at part throttle, ride hard without revving the engine too high. At the end of this final break in session do another jetting pass/plug chop as described above. Check the spark plug for the correct dark/rich condition. Wiseco Piston equipped engines will require another one or two break in cycles, ride at a recreational pace not revving the engine hard, full throttle should only be used for very short periods, fifth and sixth gear should only be used to cruise, ride one tank of gas through the engine in this manner to complete the break in. We feel it take about two gallons of gas to break in a motor equipped with a cast piston and five gallons for a motor equipped with a Wiseco.

8) Replace the spark plug with a new one, ride the bike aggressively for eight minutes and do a jetting pass/ plug chop in fifth gear. If the porcelain color is still dark/rich, lean the main jet size one at a time until the smoke ring at the base of the porcelain is a light brown. If the porcelain base is white, donít run the engine and contact CT. If the plug color looks good, continue riding at a race pace for ten minutes. Stop and let the engine cool. Check the torque on the cylinder base and head nuts.

9) More on jetting. If you generally run your engine flat out in sixth gear then make your jet pass/ plug shop in sixth. Motocross jetting is checked in fifth gear, therefore it is not safe to run MX jetting in the desert or down a road wide open in top gear. Desert jetting is richer than MX jetting. When running an engine at full throttle for extended periods be sure to chop the throttle decisively to slow down, just rolling out a little can seize a well jetted engine.


CT racing 11805 E. Slauson Ave. Santa Fe Springs, Ca. 90670 ph. 562.945.2453 fx. 562.945.7006