Engine Assembly
Two Stroke Top End Rebuilding
# Start out with a clean workspace.
# First insert the piston rings into the cylinder about an inch down from the top, use the piston to center them into the cyl. Used a feeler gauge to check the ring end gap. check to see that the gap has the required end gap specs. Grinding of the ring ends may be necessary.
Installing Rings & Piston:
#Install the rings onto the piston making sure the end gaps line up with the locating pins on the piston. If there is a marking on the rings this needs to be facing upward.
# Next install the piston to the connecting rod, The arrow on the top of the piston usually points to the exhaust side. Always use a new wrist pin, bearing and clips. Put a little 2-stroke oil on the bearing & pin. When inserting the clips make sure that the clips are seated into the grove and the open end of the clip is at the top.
# Take a clean rag and wipe the cylinder wall with new 2 stroke oil until you can wipe the cylinder and have the rag stay clean. Oil has detergents in it and is the best thing to clean metal with. Also that is all the assembly oil you will need. do not sop the piston, ring & cyl. wall with oil. This will only cause you to foul a plug on start up, fill your garage with smoke & cause the cylinder & rings to glaze, giving you poor ring seating and performance.
Cylinder Installation:
#Before setting the cylinder on to the piston be sure the base gasket surface is free of any old gasket, dirt grease etc.
# Make sure all dowl pins, o-rings and a new gasket is in place on the engine block.
# Compress the rings using your finger tips or a ring compressor. I prefer not to us the ring compressor.
# A fork shaped tool made from wood can be used to hold the piston into place while sliding the cylinder over the piston.(See Picture)
# When placing the cylinder down over the piston and rings do not twist the cylinder or the rings end gaps may get caught in a port, snagging the rings and bend or break them.
# Do Not force the cylinder down to the gasket with the nuts if it doesn't go down by hand there usually is something wrong!
Head Installation:
#Make sure the gasket surface is clean. Make sure all dowl pins & o-rings are in place, install a new gasket making sure and "this side up" markings are facing up.
# Now torque all cylinder & head nuts with a criss cross pattern, starting at 10% of the recommended torque specs. Then going to 50% then your final torque.
# Now install all carbs,(Carbs jet should always be check for correct size and that they are clean) exh. head stays, motor mounts etc.
# Put new coolant in machine.
# If machine has set for more than a month I recommend putting a fresh gas\oil mix in tank. (see our lubrication page for recomended oils & mixtures.
# If machine is oil injected you must bleed all oil lines making sure there is no air bubbles in the lines. Mix the first tank of fuel with a 50:1 oil mix along with the oil injection in case there are air in oil lines. Be sure oil pump cables are connected and adjusted.
#Clean The Carb! E10 - Means 10% Alcohol in your gas! Soon maybe E15. Alcohol absorbs and hold water. Water enters your gas thru the tank or gas can vent. No you cant just plug the vent or the tank will bulge out or be sucked in and possibly split. When air is vented in, it also draws in water from humidity. The alcohol absorbs the water and separates " Phase Separation" Since the octane is boosted these days by alcohol, the octane level is lowered by as much a 3 points. Adding more alcohol such as dry gas will make matters worse. The water Alcohol mix will lay in the bottom of the tank and the engine will not run.
Storage - Gas stored as little as one month will separate. So now days use a smaller gas can and use it up. The gas in your motorcycle chainsaw Etc. tank should be drained and the tank will need to be fogged with oil so it doesn't rust. also the carburetor should be drained or run dry. Beware of Sta-bil and similar products, They Don't Work!
E10 will also loosen up gum, varnish and cause it to get logged in jets, causing a piston melt down from the too lean condition.
Fuel left in carbs for a long period of time will leave deposits in the carb that cannot be cleaned by soaking in carburetor cleaner. They will need to be clean in an Ultrasonic Cleaner. Ultrasonic cleaners are very expensive.
Avoid Seizure - In your two stroke do not use high octane from the pump, it contains more alcohol and runs leaner. Use reg grade and use a good octane booster such as Klotz. Also Always use a synthetic oil in the Injection System and an 1/2 ounce of oil per gallon in the tank as well. Ethanol is a solvent and washes away the layer of oil between parts. The above method will help avoid premature engine wear.
# Now you want to review our "Engine break in page" for initial engine start up and break in.
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