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I am a super experienced 2 stroke guy and I have good news and bad news for you. The good news is that with a few tools and a bit more investment you can have a really good ride. The bad news is that as is, the new chinese two stroke (48cc and 66cc) are poorly designed and need some parts machined and some parts replaced.  Things you need to do: Enhancing the stock setup (do these before spending big money on parts and porting the engine) 1. If the engines head is separate from the cylinder then use sandpaper on glass to plane the head surface flat and increase its compression a little bit for more power. Press the head onto the sandpaper while moving it in a circular path. Also make your own head gasket out of high temp gasket material for it to seal properly. 2. If the engine vibrates then drill a bigger hole in the wrist pin with a 7mm carbide bit at a machine shop (using a lathe) for less vibration. Without this the engine will always be unrelible as it will shake loose nuts and bolts. Also a vibrating engine makes it uncomfortable to ride. If it still vibrates too much then you need to drill holes into the crank wheels with a 3/8" carbide bit which is explained on this page. 3. Take the screws off of the stator coil and clean off the shellac on those screw head contact areas. That is important because that screw to metal contact is the ground path for the high voltage coil and spark plug. The worse the contact is, the weaker the spark will be which reduces engine power. 4. Replace the stock nuts/bolts/studs with a replacement kit from Sick Bike Parts. The stock ones are too buttery and will strip threads and break off. Also apply medium strength thread lock to all threads. 5. Go to this page to read about the changes needed for the stock NT carb or the Speed carb if you have either of them. I prefer more professional carbs with a separate jet and air screw for the idle mixture but the NT is OK for beginners with the stock piston port only intake system, and the Speed Catb is good for reed valve engines. 6. Replace the no-good stock air filter with a bigger foam one that needs to be oiled with engine oil before installing. You can make your own out of carwash foam. Just use scissors to hollow it out and make it sized right to clamp it onto the carb intake. Also you can glue pieces together with silicone sealant but you can't ever clean it with gasoline or it will ruin the sealant. 7. Replace the stock spark plug with a NGK plug (#6 for cool/cold climates, #7 for moderate climates, #8 for hot climates). This gives a more consistent spark at a lower voltage for smoother more powerful running. Example: NGK BR7HS 8. Put a fuel filter on the fuel line because the filter inside the gas tank won't filter out the finer particles. Also there's usually trash inside the fuel tank that should be cleaned out before use. If not then that will partially block the filter and limit fuel flow. 9. Some fuel tank caps don't breath properly and will cause a vacuum in the tank after riding for a while which will stop the fuel flow and the engine will stop running. If that happens then drill a little hole in the top of the cap so air can enter to make up for the lowering fuel level as you ride. 10. Cut off the majority of the exit pipe inside the muffler so the engine will breath freer and run better. (actually even doing that is not enough. It really needs to be replaced with an expansion chamber.) Click here to read more. 11. Take off the top piston ring and place it inside the cylinder near the top and use a feeler gauge to find out how much the ring end gap is. If it is more than .4mm then replace them with JRL rings which have a smaller end gap. This is important because too much gap just allows pressure and power loss. 40mm dia. rings, 47mm dia. rings 12. Before using any ring you should take it off the piston and use a fine file or sandpaper to file the edges that will contact the cylinder at a 45 degree angle. This will prevent some loss of plating off the cylinder wall which is common. More professional rings alread have that edge angle. This also helps the rings ride on top of oil film instead of scraping it off the cylinder. 13. If the cylinder doesn't have fine scratches in it from a hone then you need to use medium grit sandpaper to rough up the cylinder surface. This helps the rings wear down to conform to the cylinder and in this process the sratches disappear to not continually wear down the rings. Having the rings conform perfectly to the cylinder prevents blowby which robs power and heats up the piston too much. 14. After all this, break in the engine using mineral oil to seat the rings properly. Read more Once you get these mods done and want the engine to start easier, run smoother, and have better top speed then think about the following possibilities: Making It The Best It Can Be 1. Get an exhaust pipe that is an expansion chamber. When its length is correct (16" centerline from piston to beginning of baffle) for a stock engine it will boost engine power for another 1300 RPM right when the engine by itself would poop out. Click here to read more. 2. Put a good carburetor on that is fully adjustable such as the Mikuni VM18 or Dellorto PHBG17. If you port the engine and balance the crank then you might consider the Oko 21mm carb. Click here to read more. 3. Put on a good aftermarket CDI that will help the engine rev out. The best one is my Performance CDI, and second best is the Lightning CDI. 4. The most technical mod you can do is buy a rotary tool with cutting discs and mod the cylinder ports for more power. You can widen the intake and exhaust ports and lower the intake port (or take some off the bottom of the pistons intake skirt) so that it has a bit longer open port duration (120 degrees) which gives it more power all around. Click here to read more. All of these mods are fully explained on this sites pages. Click the home link and start reading. |