Engine Trouble M bike troubles

Discussion in '2-Stroke Engines' started by mrfman3, May 16, 2012.

  1. mrfman3

    mrfman3 New Member

    Posted this in 'introduce yourself section and got sent here:
    After sitting for the last couple of months I once again pulled out my motorized bike. Before taking a break from it cause I got fed up with working on it, I had put a new carb on it, just like the one that came with it. As well as replacing the piston rings, and the cdi. Troubleshooting and more troubleshooting. I've adjusted the clutch plate once again as the most recent problem has been that the clutch wouldn't turn at all. Upon taking a look at it the other day I force turned the gear that turns the chain. That freed up the clutch plate, I guess with the new piston rings on, it had just gotten stuck. So cool I tried to start it and whalla! it ran... for about half a mile. Then went back to its state before I put it away, it won't go. So back to basics. I made sure the carb jets were clear. Yesterday I used some gasket making material along with the grommet to make sure the carb is snugged up to the intake. As well as putting some gaskets between the metal plate that fits in the top cylinder head area since I figured maybe having taken it on and off had opened a gap somewhere. Yesterday I kept walking it up a hill and attempted starts down, after a few tries it would run a bit as long as the throttle was cranked and I was pedaling and going downhill, but would die immediately as I began to head up hill. I messed with the choke as well as the screw on the side of the carb, but that doesn't seem to be the problem. I'm in a corner here as to what the issue is so that's why I've come here to hopefully get some resolution as to why this thing won't stay running. It's a blast to ride, but it's been me bashing my head into the wall with one problem after another, pretty discouraging. The muffler blew into pieces one day last summer, that's replaced also, that was a good one. At least I shot a few feet in the air when that thing popped!

    that said it's a 80cc kit which is actually 60 from what I've read. I got it on ebay and don't know if it has a brand.

  2. motorpsycho

    motorpsycho Active Member

    the clutches on thes engines will stick when they sit for a long time. They sit in boxes on shipping docks or in shipping crates for months exposed to moisture.
    this alone will make the clutch stick.
    it has nothing to do with the new piston rings.

    the screw on the side of the carb is an idle speed adjustment screw (if you have the n.t. carb anyway).

    you need to make sure that you have fuel flowing out of the gas tank at a decent rate...not dripping. remove the gas line from the carb and put it into a can. Open the petcock on the tank and watch the flow of fuel. if it drips or comes out slow, the petcock or the screen in the carb (on the end of the petcock) may be clogged up. if you're running an in line fuel filter, make sure that it's not clogged up.

    Make sure that your throttle slide is installed the right way. It can go into the carb 2 different ways, but only one way is correct. the long slot in the slide goes to the right (while looking down at the carb) and it lines up with a pin inside the carb body.
    make sure that your choke is actually opening and closing...sometimes they will stick closed or not open all the way.

    so you're saying that you added gasket material between the cylinder head and the cylinder (as in head gasket?)
    what kind of material did you use?
    if you added more than the thickness of the stock head gasket, you just lowered the compression by quite a bit. a low compression engine will not want to run very well.
    all you need is the stock head gasket which is very thin.
    if you were peddling, the engine probably wasn't running on it's own. your peddling was making the engine run and it may not have even been running...you were just making it turn over and sound like it was running.
    unless you were able to ride it without peddling at all.

    check your wiring, make sure that there are no bare wires touching anything. if you used the kit supplied wire connectors, get rid of them...they are junk.
    solder all wire connections and cover them with heat shrink.

    turn on the gas and leave it on for a minute. then remove the carb and remove the float bowl. make sure that it's full of gas.
    make sure that your needle & seat isnt stuck closed, and make sure that the main jet isn't laying in the bottom of the float bowl.
    make sure that the hole in the main jet is clear because a TINY bit of dirt in the main jet can make it not run.

    Make sure you have good spark at the spark plug. If you have ANYTHING hooked to the white wire (like a headlight), cut the wire off, because it will steal power from the magneto and cause the engine not to run. make sure the end of the white wire is capped off so it can't touch anything.

    check the gap on your spark plug, it should be around 25 - 28 thouandths. if you're still using the china spark plug that came with the kit, get rid of it and put an ngk plug in it (b6hs works good for me).
    make sure that the plug wire is fully snapped onto the spark plug, and if you're still using the kit supplied spark plug wire...they are peices of junk as well.

    if you bought the engine off of e-bay, yes...it is a 66 c.c. they call them 80 c.c.'s but in reality they are only 66 c.c.'s.
    they also made a 49 c.c. but if you bought it as an 80/66 c.c. then chances are that's what you have.

    there are a ton of things that can cause these engines not to run, but cover the basics, and then go from there.
    Last edited: May 16, 2012
  3. mrfman3

    mrfman3 New Member

    Thanks very much for the informative reply. I'll be checking the gas flow and be doing some soldering right out of the gates as those both sound like current possible culprits. And then work through your recommendations and see what happens.