49cc 2 Stroke engine gummed up

Discussion in '2-Stroke Engines' started by C.C.Rider, Aug 12, 2011.

  1. C.C.Rider

    C.C.Rider New Member

    Hi everyone,
    I just picked up a 26 inch mountain bike with a 49cc 2 stroke engine that has been sitting for awhile. The gas in the tank has turned, throttle doesn't want to move,top of plug is broke off.
    The broken sparkplug is why it was parked. Since this a 2 stroke engine, can I use carb cleaner to clean carburator, and gas tank? Or is there something specific to use only on 2 strokes engines? Also since 2 stroke gas goes stale after a short time, should I just mix the fuel directly in the tank on the bike?
    Many thanks,

  2. motorpsycho

    motorpsycho Active Member

    yeah you can use regular old carb cleaner to get all of the gunk cleaned out. take the carb all apart and soak everything that's gummed up in carb cleaner.
    Make sure to check ALL of the little holes iside the carb and run a thim peice of wire through them to make sure they are all unclogged. Run a wire through the main jet as well to make sure it's clean. I woudl also replace the fuel line and get a good inline filter.
    Drain the gas tank and make sure there's no chunks or rust inside of it. remove the petcock from the tank and if it has a screen on the end, take it off. Thise have been known to fall apart and clog up the petcock. when you put the petcock backn into the tank use teflon tape or a thread sealer on the threads but make sure it can withstand gasoline. you should also install a fiber washer on the threads where the petcock seals against the gas tank. If it has one and it's ok, just re-use it. but you can find fiber washers at the hardware store.

    if the throttle doesn't want to move it's quite possible that the carb slide is gummed up. when you take the carb slide out, pay close attention to how it came out and make sure you put it back in the same way (pay attention to the slots in the sides of the slide). the long slot goes to the right side (when looking down at the carb from the top) and it lines up with a pin that is pressed into the inside of the carb body. the short slot in the slide lines up with the idle screw on the left side. the slide can go back in 2 different ways, but only one way is correct. if it's put in wrong the slide can bind up and not move, or it can get stuck at wide open throttle.
    also, lube the throttle cable with penetrating oil (not wd-40) and work it back & forth to free it up. squirt some penetrating oil down into the cable between the sheath and the cable itself.
    you should also clean the air filter while you're at it.
    get an ngk b6hs spark plug, and you should also consider swapping out the stock spark plug wire for an automotive style one with a rubber boot on the end. the plug wire just unscrews from the black cdi box. (the stock spark plug wire is junk and isn't even a real spark plug wire to begin with). just twist the wire to the left to take it off (you will see a screw in the cdi box where the wire screws onto) screw a new wire onto the cdi but make sure that the screw goes into the center of the plug wire and not into the insulation or you won't get any spark.
    Mix up your oil-gas in a regular gas can and shake it up good.
    if you mix the oil-gas in the tank it may not get mixed up enough and the oil may settle to the bottom of the tank. this would cause too much oil to go into the carb and the engine will run terrible or not run at all.

    since you bought this bike already built, you should also take some time and go over the nuts & bolts on the engine mounts and the rear sprocket to make sure they are all tight and that none of them are broken. be careful tho because if all the stock kit supplied nuts and bolts were used, they can break easily because they are very low quality. The best thing to do(if it hasn't been done already) is to replace all of the nuts, bolts and washers with some better quality ones from the hardware store and use blue loc-tite on all of them.
    you should also check the grease in the wheel bearings, and the wheel bearing adjustment.
    If it were me, i would clean, re-grease and adjust all of the bearings on the bike itself (wheels, cranks, and headset) because you never know what the previous owner did and maybe he never even bothered to check any of the bearings.
    check and adjust the brakes to make sure they are working good before you even get the motor running.
    just be careful and give the entire bike a once over just to make sure everything is tight, adjusted right and that nothing is broken.
    Last edited: Aug 12, 2011