dont get me wrong if they put in the instructions that i could run in in just 50 miles i would coz i dont think anyone likes the running in period lol
if you think about it your crankshaft is doing somewhere near 9000 rpm on normal running. So your piston is going up and down 300 times a second. So it won't take long to run it in lol
Okay I'll tell my opinion about this subject, from my experience: The things you need: - Correct piston-cylinder clearance - Quality piston, not some cheap chinese - Use some smooth sandpaper on all the edges of all the rings - Lubricate, use 1:40 mixture on the first 100 miles If you got all these, running in shouldn't take longer than: - 70~80 miles if cylinder is cast iron - 2~3 miles if cylinder is alloy, with "nicasil" or hard-chrome coating Two heat cycles (get it up to 60°C, let it cool, do it again) applies to all kinds of cylinders.
the first few minutes are the most important, sorry if I'm telling folk to suck eggs here but would rather help someone who is new to rebuilds. Use lots of two stroke oil when rebuilding, especially the small end bearing. and coating the piston, piston rings, gudgeon pin and the inside of the barrel. When you have rebuilt the top end turn it over by hand with the ignition off and the spark plug out until you think things have settled, then use the starter motor with the plug out, about twenty cycles, 4 or 5 times, putting a drop of two stroke in the plughole a each time, then complete the rebuild. It might take some extra turns to get it started until the crankase gets the right mix, and you will get a lot of smoke and an oily plug, but completely worth the extra effort, then once started (as above) let it heat up on idle to running temperature then turn off, let cool then repeat at least three times letting it idle for a minute then turning off. For your first 5 miles on the road go as slow as possible, then retorque the cylinder head bolts and exhaust bolts when cold. once things have got near to getting back to your normal mix (as above) add a little extra 2 stroke to your first few litres of fuel. This will ensure you have a good basis for the rest of the run in period. treat it like a baby (lol). also always worth washing the crankcase out with a mix of petrol and two stroke (10:1) when the cylinder is off. don't overheat the engine, and keep it at low temperatures. the difference for motocrossers is some racers change rings every race, whereas if your like me you want to depend on your machine to get you home in the pissing rain in the winter (lol)
Some great info here! Saves me running in my new kit for 500 miles like my Ts50x Autisa kit!! Back in 1992 that was a pita. Wish I’d known this back then.