Piston install/break in/jetting info HERE! >>>

[Lakeshore]

FYI - Here is the blurb we supply with all outgoing rebuilt cylinders. Hopefully this will help some of you....

IMPORTANT INSTRUCTIONS!!

Thank you for choosing Lakeshore Industries for the reconditioning of your cylinder! Below, you will find a list of procedures designed to maximize the potential of your newly reconditioned cylinder. Failure to follow these instructions voids the warranty. AND REMEMBER! – GAP THAT RING!

IMPORTANT: Prior to installing your cylinder, make sure your cylinder bore and surrounding areas are completely free from dirt & debris. If you have no powervalves or they are not installed, WASH your cylinder in warm, soapy water to remove any residual material otherwise, completely wipe down your cylinder with the rag supplied being as thorough as possible. The solvents and oil used in the reconditioning process leave a residue which helps prevent rust but can also pick up dirt and grit. Dirt is an engine’s worst enemy. Take your time when re-assembling… DO NOT force any screws, nuts or studs. Aluminum is a relatively ‘soft’ metal and can be damaged easily. If you encounter resistance, remove the stud/screw/nut and inspect and clean the threads or hole as necessary.

PISTON INSTALLATION

NOTE: If your cylinder has an exhaust bridge, it has been relieved for you. If you have an exhaust bridge, Wiseco recommends that the piston be ‘pre-drilled’ on the exhaust side to aid in lubricating the exhaust bridge. (See the paperwork in your piston kit.) Most pistons come ‘pre-drilled’ by the manufacturer. If yours is not, then you must follow the instructions provided with your piston kit.

1) Always use new gaskets for assembly. Clean all surfaces that are to be mated. CAUTION: No gasket material should be exposed in the cylinder bore.. We do not recommend gasket material for anything other than METAL head gaskets and even then it may not be necessary. If both surfaces are uncompromised then the gasket should suffice.
2) The single biggest mistake that is made during re-assembly is the failure to check ring gap! Check ring end gap by inserting each ring into the cylinder bore and measuring the gap with a feeler gage. A minimum of .012” or 0.3mm is recommended. This step is critical as with too tight a gap, ring seizure will occur.
3) Install piston with rings and circlips on the connecting rod with arrow on top of piston ALWAYS TOWARDS EXHAUST. It is highly recommended that you replace the wrist pin and top end bearing if either is showing signs of wear or discoloration.
4) Lower cylinder on to piston. If piston is pinned on the intake side, special precautions must be taken to avoid ring tip breakage or scarring of the bore. Remove reed cage and lower cylinder until you see rings through the intake port. With a wooden dowel, press against the ring tip. Lower the cylinder allowing the cylinder to slide easily to meet the crankcase.
5) Torque cylinder and head to factory specifications.
6) Use a new sparkplug and clean the air filter and intake system prior to break-in.

BREAK-IN PROCEDURES

1) Start your engine and let it 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 for five to seven minutes at a very easy pace. Vary the RPM and do not ride at one speed. Do not ride at more than 1/3 throttle or more than 1/3 RPM. Let the engine cool down and repeat the initial break-in ride. Let the engine cool down.
3) Check the cylinder base and head nuts for proper torque. Check the engine coolant level and add as necessary.
4) Ride the bike for five to ten minutes at a moderate pace. Very the RPM and do not ride at more than ¾ throttle or ¾ 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 thru the gears. Once the engine is up to operating temperature, you can make a jetting pass or ‘plug chop’. 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 the clutch and stop.
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 on the length of the porcelain to its base. There should be a dark chocolate colored smoke ring. There was not sufficient time to thoroughly color the entire 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.
7) Complete the break-in by riding at an aggressive pace for fifteen minutes. Vary the RPM and do not cruise at part throttle. Ride hard without revving the engine too hard or too high. At the end of this final break-in session do another jetting pass as described above. Check the spark plug for the correct dark/rich condition. Finally, ride at a recreational pace not revving the engine hard. Full throttle should only be used for very short periods. Fifth and sixth gears should only be used for cruising. Ride one tank of gas through your engine in this manner to complete the break-in.
Replace the spark plug with a new one. Ride the bike aggressively for eight minutes and do a jetting pass in fifth gear. If the porcelain color is still rich/dark, lean the main jet size one at a time until the smoke ring at the base of the cylinder is a light brown. If the porcelain base is white, do not run the engine and contact Lakeshore Industries for further assistance with your carb set up. 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. If you generally run your engine flat out in sixth gear, then make your jetting pass in sixth. Motocross jetting is generally checked in fifth gear, therefore it is not safe to run MX jetting in the desert wide open in sixth. Desert checking 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.

The best top-end overhaul, done by the most qualified mechanic, is only as good as your break-in procedure.