how to change a piston on a 2 stroke dirtbike without running broke.?

Answer 1

They're incredibly easy to change and top shelf pistons ( JE ) aren't expencive either.

Remove the carb. and exhaust pipe(s). There are 4 screws securing the cylinder to the crankcase remove them and lift the cylinder off. The piston wrist pin has either an internal snap ring which you'll need a set of snap ring pliars to remove them with. Some wrist pins have a small cir-clip that can be removed with a fingernail or an eye glass screwdriver. Slide the wrist pin out and carefully check the needle bearings for damage and wear. If I were you replace the needle bering cage inside the rod when re-installing the piston. Check the surface of the cylinder sleeve for scoreing. you may need to have the cylinder re-honed for the next larger sized piston. Be careful who hones the cylinder. The piston maker will suggest the finish needed for the piston rings being used. Most engine speed shops will hone and triple check the ring end gap for you. Don't skimp here because the rings and finish inside the cylinder make a or break 2 cycle motors. Most pistons and rings come in .005 -.010 oversizes. Use a new crankcase gasket if equipped (some have no gasket). In any event use anerobic red spray where the cylinder meets the crankcase and carefully slide the 2 cycle oiled piston onto the cylinder. By squeezing the rings the piston slides all the way in the cylinder. Tighten up the 4 cylinder bolts and hook up the carb.

Good luck. You are ready to ride!

Answer 2

First off, running a 4 stroke without an exhaust will NOT burn an exhaust valve. Why should it, the exhaust has practically no resistance and can get away in a hurry. Too much resistance (back pressure) in the exhaust will cause an engine to overheat because the heat can't get away. Look at dragsters and you'll find they run straight pipes that provide very little back pressure at all. Maybe someone ought to do them a favor and tell them they don't know what they're doing. As far as a 2 stroke goes, the muffler or expansion chamber plays a vital role. An expansion chamber is tuned to the particular engine and the desired rpm for producing peak power. They don't function by creating back pressure, rather they reflect the exhaust wave back toward the engine and then back again towards the outlet. This second reflection at they exhaust port causes the wave to help pull the next exhaust pulse out of the cylinder, thereby improving scavenging. Expansion chambers can increase power at a certain rpm range, but will also reduce power at other rpm ranges. That's because at those particular rpms, after being reflected the first time, the wave hits the exhaust port too late and tries to push the next exhaust pulse back into the cylinder. Without a muffler or exhaust system, your engine will run badly or be totally unmanagable. I once took the muffler off of a chainsaw and it would run full throttle even with the throttle closed. Opening the throttle had absolutely no effect upon engine rpm. Incidently, reflected wave exhausts are used on 4 stroke engines as well. Look at a dyno chart and some engine will actually lose power at a certain rpm before increasing again. That's the rpm where the reflected wave is out of sync with the exhaust valve opening.

Answer 3

There is no way to do this without spending some money.

To do the job right, you need at least a new piston, rings, gaskets, and hone the cylinder bore.

Some 2 stroke engines have a special high strength plating on the bore surface that needs to be re-done too.

http://www.maxpower-engines.com/big-bore-kits/kits_125.htm

Answer 4

Just rid of it now to save money. Get yourself a 4 stroke in the future to combat this problem.