Trouble starting 66cc motorized bicycle!

Discussion in '2-Stroke Engines' started by Kallinikos, Jul 4, 2011.

  1. Kallinikos

    Kallinikos New Member

    Hii guyss, so i recently built a 66cc motorized bicycle and have some trouble starting it. My friends bike starts as soon as he drops the clutch but my bike take around 5 mins to get it to start. I ride up and down my street releasing the clutch trying to get it going. You can hear he motor trying to tick over but not getting there. My fuel mixture is 16:1 for initial run in. Any ideas why this is happening? :icon_cry:

  2. retromike3

    retromike3 Member

    fuel, air, compression, spark repeat

    These basic things you need to keep riding the bike up and down the street if you point the bike up in the air does gas drip out the exhaust pipe?he said been riding the bike for a bit, so it should have plenty gas.

    If it does that means it's got gas and I bet it's got air, so the next thing to do is to pop the the spark plug off lay it on top of the cylinder with the cable attached to it from the CDI. let out the clutch and look for spark. I usually do this when the bike is in a stand. I had a similar problem with the last motor I got. I tried riding it in riding it and nothing happened. I took the spark plug out laded on the top of the engine and tried the test. I did get a spark,but it turned out that it wasn't strong enough. When I replaced the CDI it took right off. Later I had problems with it because the connectors were not holding on very well so, I soldered the connections together and then wrapped them with electrical tape.

    Lucky for me I had an extra CDI Laying around,if yours is bad I would send it back to wherever you got the kit from and hopefully will give you another one and they might even pay for the shipping.

    Good luck.
    Last edited: Jul 4, 2011
  3. Skyliner70cc

    Skyliner70cc Active Member

    It'll start easier with 32:1 fuel to oil ratio and easier once it is broken in. Don't use full choke. As you are pedalling or running down hill to crank engine, use left hand and reach over to find that sweet spot that will cause engine to start. Mine is just below 1/2 choke.
    Last edited: Jul 4, 2011
  4. Big Red

    Big Red Active Member


    First things first. Get rid of that thing the chinese called a spark plug and go get a medium range NKG. Or a better brand if you know of one. Then check your spark. Next, Make sure it IS getting gas. The carbs arent always ajusted right when you get them. You can try dropping a LITTLE gas right down the carb throte. If it POPS then check out the carb. Get back to this site for info on carbs. I just saw one the other day by stan4d that was very good.
    If it don't POP then check out the CDI unit. They are good for being bad.
    That SHOULD do it. If not, again, get back here for more info. Most of these guys really know what their talking about.
    Big Red.
  5. Kallinikos

    Kallinikos New Member

    Thanks for all the help guys :) I found the problem in the end. Spark plug didn't have enough spark, replaced it with another and it works fine :)
  6. motorpsycho

    motorpsycho Active Member

    you should also consider getting rid of the stock spark plug wire because they are junk. they are nothing more than a peice of copper wire with so called insulation over it.
    you should get an automotive type spark plug wire with a rubber boot instead of the stock one. if you go this route, you will need to screw the top cap back onto the spark plug for the autromotive boot to snap onto it. the stock plug wire just unscrews from the cdi, and you can screw a new wire onto the cdi. just twist the plug wire off of the cdi (lefty loosey) and you will see a screw inside the cdi. now just screw the new wire onto the screw and you're done.
    make sure that you're spark plug gap is set right also.

    also, if you used the push together connectors for your wiring, you should cut them off and solder all of your wire connections together, and then heat shrink them.
    the stock push together connectors will fail over time because they will vibrate loose or break apart.
    make sure that the white wire is not connected to anything (like a headlight) and make sure that the end is cut off, and capped. make sure that there are no bare wires touching anything because this can give you headaches and have you chasing ghosts trying to figure out why the engine won't run.
    it's harder for an engine to start on 16:1, but it should still start up fairly quick. when you go to 32:1 it'll start even better and once the engine is broken in, it'll get even better.
    then you get to mess around tuning the carb, and modifying stuff to make it
  7. Huotalicus

    Huotalicus Member

    engine wont start FIXED

    guys check the magneto coil......... thats what happened to mine and it was frustrating for 2 months ........finally figured it out, you need a good spark and good CDI.... vibrationc can short them too...always take the white wire off...its a shorter for the engine..nota good idea...if it touches any part of the will short your enigne out... and if you dont know thids it can drive you crazy ..aso with plug,,makes ure strong spark not just a spark... diffrence between coil dead and cdi dead ...if your hand zaps with cdi in hand..itrs fried......
    AIR FUEL SPARK 1 ... 2.... 3... SIMPLE AS...HONESTLY.....YOUD KNOW IF A PISTON RING WERE GONE OR IF A GASKET BLEW, YOUD FEEL THE AIR LEAK...i must say one engine i had for 3 months non stop and it wouldnt fire....i changed spark plug..changed cdi and the coil but no go... then i used a cooil from a machine that wasnt working also...and that made it worse..thinking it was fine...those magneto coil can blow quite easily or shake right off