Bike starts up fine, bogs out after 100 ft , major pain to start up again

Discussion in 'Motorized Bicycle Trouble Shooting' started by Mr buenomoreno, Feb 13, 2017.

  1. Mr buenomoreno

    Mr buenomoreno New Member

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    Hey guys so this is my second build, I had a 80cc engine on a 90s mountain bike which ran perfectly no problems and did me well for about 3 months, the motor was fine but the bike itself had gave out, now I have transferred the same motor to a beach cruiser and to my dismay I can't get the damn thing to go for more than a minute without bogging out, ive already took apart and cleaned the carburetor installed brand new fuel lines Cleaned out the filter in the gas tank so fuel flow is probrabrly not the problem, I've cycled through different settings on the jet needle with no luck, I also am using a brand new spark plug , I checked the wiring on the spark plug cap and cdi they are ok, I'm really lost any help is greatly appreciated
     
  2. crassius

    crassius Well-Known Member

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    does it smoke a lot when it runs?

    is motor tight in frame and frame not cracked so carb doesn't shake?

    when it quite, is spark still there?

    had similar here a while back, turned out that rivets in armature weren't tight, so after a while spark stopped but came back as soon as it could cool just a bit - that doesn't seem likely tho if motor ran in other frame for 3 months
     
  3. Mr buenomoreno

    Mr buenomoreno New Member

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    it barley smokes
    The frame is somewhat tight so you culd be on to something with the vibrations
    once it dies I can hear the motor cranking but theres no spark for at least 5 to 10 minutes then the cycle continues runs like a champ for 1 min or so then dies , could this be an issue wth the magneto or cdi? Because those were giving me grief when I first did the build and had to replace them
     
  4. Chaz

    Chaz Active Member

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    There's a good "no start" thread here somewhere that may help. It sounds like a fuel delivery problem. Either too much or not enough. Check the float level, maybe the tang was installed upside down when you re-assembled the carb.

    my money is on the carb... mix, ratio, float level, blockage, choke issue, air filter clogged?
     
  5. crassius

    crassius Well-Known Member

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    could be bad mechanical ground in mag - you might want to file armature for shiny metal at contact points and be sure all 4 screws are tight - if wire soldered to armature from coil is loose, it sometimes makes contact just from its weight, but can lift off when motor vibrates
     
  6. Mr buenomoreno

    Mr buenomoreno New Member

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    Chaz I will take apart the carb again for good measure who knows maybe something is blocking the fuel flow that I didn't catch the first time
    And crassius I checked the soldering on the mag and come to find the blue wire connected by half of the original wires.....but still connected.... ,swapped it out for a older one will check it out tomorrow because it's almost midnight and I don't want my neighbors complaining about the noise, I will also post pictures of the bike before and after the frame swap maybe there's some answer hidden jn the pictures
     
  7. Mr buenomoreno

    Mr buenomoreno New Member

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    Also choke is working fine ,air filter clean, ratio is 20:1
     
  8. Chaz

    Chaz Active Member

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    Three months is enough time to break in your engine so you can thin your gas/oil mix to 32:1 Won't solve your problem but the thicker mix may be contributing to the problem.

    Do a little test, turn on the gas at the tank petcock and let the carb bowl fill up, about 10 seconds. Then turn off the tank petcock and try to start it up. See how long it runs and how it performs.
     
  9. xXNightRiderXx

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    I had this issue once. Thinned out the mixture and my motor ran just fine after.
     
  10. Mr buenomoreno

    Mr buenomoreno New Member

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    Ok so I replaced the magneto because the connections broke off and the bike runs for a bit longer but now it has very weak power and , it doesent idle , also when I was breaking the engine in the muffler broke off but the exhaust pipe is still there, this wasnt ever a problem before with the motor on the previous bike I just raised the jet needle to compensate for exhaust escaping more rapidly, since I've moved the motor to another bike I placed the clip on the jet needle on the second from the top ,could this be the reason for my loss of power
     
  11. Mr buenomoreno

    Mr buenomoreno New Member

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    Night rider are you talking about thinning the gas/oil mixture?
     
  12. Mr buenomoreno

    Mr buenomoreno New Member

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    Ok so far i replaced the cdi and mag because the bike was left out in the rain,
    Thinned the fuel mixture to 4oz per gallon
    and needle clip is on the line second from the bottom , I tried it out and it ran decent for about 5 minutes but it still won't idle so when I engaged the clutch it turned itself off and I tried to start it right after and wouldn't turn back on unless I pedaled ridiculously hard and long( before 2 good cranks would start it right up again) and when it did turn on it was very weak and bogged down minute later,once again not sure what it could be , does the carb have to be at a specific angle because mine is sitting fairly level right now?
     
  13. crassius

    crassius Well-Known Member

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    if it won't idle with screw turned all the way in, that often means you are too rich - try moving clip right to top of needle to see how it runs - if that helps, then try moving clip one notch at a time to find best spot
     
  14. Potato_In_Exhaust

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    Sounds like a fuel problem to me.
     
  15. xXNightRiderXx

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    I run my engine at 2.5oz per gallon, and it runs perfectly. This is about half what I was using when my engine started bogging down.
    Update: I have my needle now set to the top notch. She started bogging down at mid rpm, too rich im assuming. One notch above middle was still a bit too rich, but I got to higher rpm than middle. We will see what happens with the leanest setting. Perhaps these may be your issue.
     
    #15 xXNightRiderXx, Mar 7, 2017
    Last edited: Mar 8, 2017
  16. Cylon

    Cylon Member

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    check your jet and make sure the float needle is sealing. also use a o ring between the carb and intake.
     
  17. Mr buenomoreno

    Mr buenomoreno New Member

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    Update,I tried it out yesterday with the jet needle on the leanest setting , it still desent idle without throttle but i was able to start it after stopping at lights for almost 2 miles with decent power not close to what it was but it sufficed then it bogged down, after it bogged needed a huge hill to ride down so I could get it running again because pedal starting it was now working, and even then it would struggle to stay running on lever ground until it bogged down again
     
  18. Cylon

    Cylon Member

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    Test the cdi, pull the boot off put a plug in it and spin the wheel while you hold the plug you should be able to tell if its weak or not working properly. I've had a bike bog out and die once and it never started again. Engine was fine mag was fine carb was fine it turned out to be the CDI it was dead somehow it just quit.
     
  19. crassius

    crassius Well-Known Member

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    It sounds like you're saying that the motor won't idle even with idle screw all the way in. Did you try the next notch on the needle and get same?
     
  20. Mr buenomoreno

    Mr buenomoreno New Member

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    Yes I've tried all the clip settings , I tried the next notch down with pretty much the same results as before
     

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