Engine Trouble Engine wont start? TROUBLESHOOTING GUIDE

Discussion in '2-Stroke Engines' started by fastboy9, Apr 7, 2008.

  1. fastboy9

    fastboy9 Member

    If your Happy Time engine isnt starting then work your way through this guide to identify and fix the problem. Still no hope? then just ask...
    With many thanks to BoltsMissing who compiled this great troubleshooting guide. Thanks to Lordoflightaz too for a few tips :)

    Firstly start off by checking that the fuel petcock is on and you have fuel. Check the wires to the CDI. Make sure that they are connected. The cheap connectors come loose

    1. Remove spark plug, check gap.
    2. Check for spark with lead on plug and earth spark plug on cylinder head fin.

    Lift the rear wheel, and give it one good hard pedal down as if you are
    kick-starting a bike. If plug sparks at the tip, re-install the spark plug. (just bear in mind that I have had plugs that fire under no compression(Not in engine)but had no spark under compression(In engine)This can be a pain if you Don't know this.You could pull your hair out with this problem,new plugs are cheap!)

    2a. If no spark, check Plug cap. I had to replace mine with a NGK Right Angle spark plug cap, (don't know the part No. though)
    2b. Repalce lead anyway with Copper wire lead.
    Check for spark again with new lead and plug cap
    That's the electrical done from start of lead to end of plug tip.

    If Spark, then go to Fuel.
    If No Spark, go to Magneto and CDI.
    But don't just replace the Magneto and CDI unless you do all the obove to.
    That way you have a clean sweep out of sight out of kind type of thing of the electrics.


    Remove Carby, AFTER Spark is all clear as explained above.
    Remove fuel bowl, see if it was full or any fuel was in there.
    If not, check fuel line and needle/seat where the fuel line plugs in.
    There may be some grit.
    If it had fuel in fuel bowl, re-fit carby.

    Fuel is OK up to fuel bowl end.

    Clutch adjustment, just go through the motions at the cable end. There should be no slack.
    Can't say much about whats behind the clutch cover, never had one with problems ,yet.

    By this time you probably flooded it trying to start and doing the other testings.

    Then as last resort as I mentioned earlier,
    Tow start,
    and this will "flush out" the remaining cob-webs, and it ought to go.
    Tow around the block or whatever until all reasonable doubt is undoubted if it still don't start. Be very careful though as this could be dangerous!

    Failing a tow start, then start the inspection process again the next day, so take a break, it's only a Happy Time (HT) engine.
    This time check for Head/Lower cylinder/Exhaust and Carby Gasket leaks etc.
    Point is, dwelve deeper into the problem.
    Tow again if all looks OK.

    Remember if an engine has compression, fuel (air and petrol) and a spark then it must fire, it doesnt have a choice! ;)
    Last edited: Mar 31, 2009

  2. Sockmonkey

    Sockmonkey Guest

    Sounds like the engines are junk.... Or...

    Back in the early 60's I helped my sister's husband get his BSA ready for a ride. We cleaned and polished that big single (I think it was 500 CCs) all morning. I was 14 or 15 at the time and this was going to be my first motorcycle ride so I was wound up tight when it came time to start the bike....

    Any of you who have been around British motor vehicles can see what came next, an afternoon of trouble shooting that ended with my brother in law being towed by his friend' truck. Never did get a ride that day, which was a big disapointment, but I learned that if I couldn't fix it I wouldn't own it.

    As for these little $150 engines, I was looking at electric bikes last week, but I would have to wait awhile before I could drop a grand and a half on a bike...

    Heck, last month I was in a bike shop where I saw a $4,000 bicycle! I can remember when a new Chevy cost less than that.
  3. Addicted

    Addicted New Member

    I would like to add that i have had plugs that fire under no compression(Not in engine)but had no spark under compression(In engine)This can be a pain if you Don't know this.You could pull your hair out with this problem,new plugs are cheap!
  4. KiDD

    KiDD Member

    I had a problem with my HT not starting. There were 2 problems. The first was the clutch was slipping and unable to turn the engine over. I adjusted the clutch until it could turn the engine over. The other was the kill switch dying. Remove kill switch from the equation and engine ran fine.
    Last edited: May 23, 2008
    Chuck lew likes this.
  5. fledge3

    fledge3 New Member

    wont start

    got my motor in an it ran for 10 seconds. Then wouldnt start no matter what I did. Had spark at the tip of plug. Got a new cdi an it started right up an been running good. Did a resistance check on both cdi an they were different. Like I said, I had spark but it wouldnt start.It was frustating.
  6. Ride Anything

    Ride Anything New Member


    Towed mine upto about 30 and couldn't get more than a slight tingle
    from the plug ( yes I did use the redneck plug tester and held on to it )
    I'm not sure how to find the information to test the mag or coil , can
    anyone help?
  7. MotorMac

    MotorMac Member

    hard starting

    Ride Anything, before you do anything else I suggest that you disconnect the wiring from the killswitch altogether.
    Connect the blue wire from CDI to blue from engine.( or green to green if thats what color it is)
    Connect the black from CDI to black from engine.
    Cap off the wire wire.
    Make sure that at no point anywhere that bare wire is touching any part of the frame.
    See if it starts now.
    If it does,then you can shut down the engine using the choke.
  8. Ride Anything

    Ride Anything New Member


    Wow , I love a fourm with quick responces :grin5:

    I tryed all the usual tricks with the wiring with no better results
    I was hoping somebody would tell me i forgot to remove a secret
    shipping spacer or something. As I ended up with 2 of these things
    I tried switching coils too.
    What should the plug gap be anyway ?
    thanks all.
  9. fastboy9

    fastboy9 Member

    yep its either the killswitch stealing your charge or if thats not it, then your going to need a new magneto, cos that redneck test should have sent you off your bike!
  10. Ride Anything

    Ride Anything New Member

    No kill switch so I'll have to check the mag. Does any thing like a shop manual or
    specifications even exist for these things ?
    I do have another engine I could throw in and try but where is the fun in that.
  11. fastboy9

    fastboy9 Member

    nope the speification only tells you what oil to use and the size of the engine (which is a lie anyway!!) its an electrical problem so you should first try the magneto off of the other engine and if that doesnt fix it then it must be the cdi.
  12. robin bird

    robin bird Member

    Help --engine fires wont stay running or go more than 1 minute--then quits--had no spark just put in new cdi--its a new engine
  13. arceeguy

    arceeguy Active Member

    If it runs for a minute before it quits, I would check the fuel flow to the carburetor. Sound as if the fuel bowl is emptying out, and not being replenished. After it sits for a while, fuel slowly trickles in and fills the bowl again - enough to run it for another minute or so. Could be a clogged screen, bad valve, etc.

    Good Luck!
    Archiwax likes this.
  14. lordoflightaz

    lordoflightaz Member

    Before Step 1. Check that the fuel petcock is on and you have fuel. Check the wires to the CDI. Make sure that they are connected. The cheap connectors come loose
  15. fastboy9

    fastboy9 Member

    Thanks lordoflightaz, ill add that to the guide! something so simple but often overlooked :)
  16. lordoflightaz

    lordoflightaz Member

    I am smart enough to turn off the fuel petcock, but a lot of times I am too stupid to turn it on.

    When I replace the CDI connections, I wire one backwards so I can't plug them in black to blue
  17. crazycrawler

    crazycrawler Member

    Won't Start

    I am having the same problem. Got spark, got gas but no go. I'm going to check the magnet next to see if it might be installed backwards. I don't know what else might be wrong. These things can drive you crazy.

    The Crawler
  18. preston

    preston New Member

    hope its alright i'm posting in an older thread, but just have a few questions...

    okay, so i shocked myself testing the spark plug (idiot), so i know thats working.

    the clutch works great, i can feel and hear it turning the piston when i try to start the engine, so thats not the problem either.

    what i have come to think is that it is a carb or throttle problem

    i get the engine to turn over, hear it start firing, but as soon as i pull in the clutch it cuts out.

    things i have already tried:
    the fuel line is 'on' at both the tank and the carb, i used the tickler button and could see gas flow down the line (an air bubble anyhow).

    PS, glad to be joining the MB community :D
  19. preston

    preston New Member

    never-mind... i managed to fix it.

    for anyone that has the same problem:

    use the in-line screws on the throttle cable to make sure it is tight. screw IN the idle adjustment screw, open the choke by pushing it DOWN.

    I don't know which was the problem, as i did them all, but i got it goin :D

    don't forget to push the primer button either.
  20. Sachs-rider

    Sachs-rider New Member

    check list - it can only be: FUEL/IGNITION/COMPRESSION/TIMING

    Quick check list on troublesome starting..
    1) Fuel, Oil --no fuel, too much oil.
    2) Fuel Pipe-blocked.
    3) Fuel filter-blocked.
    4) Carb stop cock/control cable-damaged, maladjusted.
    5) Carb choke/control cable-damaged, maladjusted.
    6) Carb needle valve - fouled, damaged, blocked
    7) Carb jets- fouled, damaged, blocked
    8) Blocked air filter
    9) Flooding carb - Fouled needle valve
    1) CDI wiring/connectors - connected wrong, disconnected, damaged CDI.
    2) Ignition coil/pickup/connectors-damaged coil, wires, loose screws on coil.
    3) Spark plug/cable/connector - Fouled, damaged plug, damaged cable or connector
    4) Carb Kill switch-stuck in Kill position inside carb, wire shorted to chassis, control plunger.
    1) Spark plug (Loose fit, gas escaping) ( make sure plug hole rim is clean, tighten plug with a torque wrench)
    2) Cylinder Gaskets, seals.
    1) Coil gap/flywheel - loose coil mounting, damaged flywheel, coil
    2) CDI UNIT-Damaged CDI, wires
    3) Reed valves

    Remember you can destroy your CDI by pulling off the spark plug with the engine running or even juct cranking the engine with the spark plug lead open circuit
    Last edited by a moderator: Dec 15, 2015