Engine wont start

Discussion in '2-Stroke Engines' started by postysteve, May 3, 2009.

  1. postysteve

    postysteve Member

    Hi Guys, hope this is the right forum for my question ??

    i've got a completely built 49cc 2 stroke bike my problem is like this :- i have only rode it a 2 or 3 times on my street and made some small adjustments to make it run and tick over better and was running good till i took apart one of the wire connectors on HT to stop engine instead of stalling it as it does not have a kill switch.

    well now it wont start at all it seems like it's not firing or trying to fire ??

    i have taken spark plug out and put it on a fin let clutch out and turned peddle to see if it will spark and it did,i have checked fuel and it's getting thro i undid screw on bottom of carb and gas comes out so fuel is getting thro to carb ok

    cant understand this as it was ok before i took the wire apart thats all i did ??

    i have gone thro the post by fastboy9 Engine wont start "TROUBLESHOOTING GUIDE" and it still wont start.

    i cant believe i'm having this trouble after just uncoupling a HT wire ?
    the connections must be ok as the spark plug is sparking out of the engine?

    it's got me puzzled ??



  2. crazeehorse

    crazeehorse Member

    if it looks like a good strong spark, i'd look to the fuel system, even though you have gas in the bowl, it may not be making it into the cylinder. is there any gas on the plug, after trying to start it. if it's wet it could be flooding, or if it's dry your carb jet could be plugged. also check to see if the pin is sheared in the magneto shaft.
  3. postysteve

    postysteve Member

    Hi Guys, Well i got it started,after doing nothing to the bike except uncoupling an HT wire i would have not thought :dunce: it would be the clutch cable that was causing the problem?

    i had check everything yesterday,then all i've done today was move the brass barrel about 1/4" inch (sorry too old for this metric stuff) and hey presto she started up so i'm well please she's running again.:grin5:

    There's just one thing i'd like to ask is wen the engine start's up and you twist the throttle it tends to lose power instead of taking off ? do you think it might be that it needs more adjustment of the clutch or is this normal while running in I.E. lack of power?

    i do know you get more power as it's running in but this does not seem right somehow or it might be just me ?

    Regards Steve.
  4. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Is the clutch slipping?
    Does the engine rev up?

    Your carb jet may be unscrewed
    Take off the float bowl and check that the brass cylinder is
    screwed in tightly
  5. Pablo

    Pablo Motored Bikes Sponsor

    Good questions - does it rev OK with the clutch disengaged (pulled in)? If not suspect a fuel flow or more likely an air leak.

    OR If it revs OK, it's just gutless from a start?
  6. postysteve

    postysteve Member

    Hi yes it does rev up wen disengaged ? wot do u mean by "gutless from a start" ?? please explain ? thanks Steve.

    Attached Files:

  7. Pablo

    Pablo Motored Bikes Sponsor

    By gutless I mean lacks any power. You start pedalling, let the clutch out and twist the throttle and it does nothing? Does it bog....as in make a "boaoaoaoag" sound and nearly dies? OR does it want to go and the engine doesn't have the power you think it should.
    Could just need to be broken in.
    From a cold engine start, the motor has no power? (cold blooded beast)
    Can you run it for a good while, ride it a good bit, then check the spark plug appearance?
    I'm trying to see if you have an air leak (too little fuel) or if you are running too rich (too much fuel)
    Last edited by a moderator: Dec 15, 2015
  8. postysteve

    postysteve Member

    Hi Thanks for your reply, in reply to your Quote above i'd say YES

    So i'm asking you don't think the clutch needs more adjustment? just need to give it more time to break in YES ??

    Regards Steve.
  9. crazeehorse

    crazeehorse Member

    what gas/oil mix are you using ?
  10. Pablo

    Pablo Motored Bikes Sponsor

    Do you feel the clutch slip? (when starting for example)

    Yes your engine probably needs some more break in time.
  11. postysteve

    postysteve Member

    Don't really know if clutch is slipping ? how do you tell ? to be honest i dont think it is sorry i'm not very mechanical, it's not been run much by previous owner or me so will have to give more runs (now i've got it going again) till it get's broken in . Thanks Steve.

    TO (Crazeehorse the mix ix 16-1 for new engines)
  12. Pablo

    Pablo Motored Bikes Sponsor

    Basically if the bike rolls with the clutch lever out and the engine is not turning over strongly, your clutch is slipping. Somewhere posted are the clutch adjustment details.
  13. postysteve

    postysteve Member

    Hi, gave it a good run today and it's a lot better today, i've taken spark plug out like you said and have taken a pic wi my moby so you can have a look at it? see attachment. pics not very good colour is like a browny/grey?

    when i got home i noticed tiny little air bubbles rising up the fuel pipe from carby wots that all about ?

    regards Steve

    Attached Files:

    Last edited: May 5, 2009
  14. Pablo

    Pablo Motored Bikes Sponsor

    Color looks sorta OK but, but it's so fuzzy, hard to tell.

    Air bubbles usually are from crappy fuel flow. Have you put an inline fuel filter in and got rid of the in tank screen (and got a better valve)?
  15. postysteve

    postysteve Member

    Hi Pablo, ya i think sparky is ok it's running ok so...... but just to go back on the tiny bubbles?? they are coming "UP THE CLEAR FUEL PIPE FROM CARBY" while engines running not down from the tank ?? just seems weird ??

    Regards Steve.
  16. Pablo

    Pablo Motored Bikes Sponsor

    Kinda tells me your tank is not venting or your flow is impeded.

    Whilst engine is running and you are watching the bubbles, loosen/remove the fuel tank cap.
  17. postysteve

    postysteve Member

    Hi Paul, well did wot u said took cap off but seems only bubbles up pipe wen i rev up ? not too bothered really as long as it runs i was just curious as to why it was happening ??

    I read somewhere in this forum that someone drilled the hole a bit bigger in the choke as they were having problems starting?

    Wen i hav got engine started i have to quickly move the choke slightly open (but only slightly)to stop it stalling do you think i should drill the hole a bit bigger maybe then it might run better wot do you think? or should i just leave it for now with it been still sort of newish ? and see how it goes on in time ?

    regards Steve.
  18. Pablo

    Pablo Motored Bikes Sponsor

    You should not have bubbles. Something isn't right. Your screen in the tank or the valve itself is impeding fuel flow.

    Never heard this. Waste of time. Just open the choke a bit more.

    This sounds normal. These engines are not at their best when cold.