spark plug preventing movement

Discussion in 'General Questions' started by HadesBike05, Apr 2, 2016.

  1. HadesBike05

    HadesBike05 Member

    Hello everyone!
    I am coming to the end of my first build and I am running into this issue and I have no clue what to do. My MB will roll forward wether or not the clutch is in but will not roll at all if the spark plug is in the engine. It just refuses to roll forward at all. I am not sure what to adjust or fix.
    Has anyone run into this issue before?

    I have never run this mb before I am just finishing initial build. No fuel has gone into the engine yet either. (not sure if relevant, just setting the stage)
     

  2. crassius

    crassius Well-Known Member

    often, a new clutch will be stuck from sitting in the crate - open the cover and see if the pressure plate moves out when you pull the lever - if so, and the clutch is still engaged, tap large gear gently with a hammer while open till it frees up
     
  3. HadesBike05

    HadesBike05 Member

    Thanka il give it a try now
     
  4. HadesBike05

    HadesBike05 Member

  5. HadesBike05

    HadesBike05 Member

    Nothing happens when I move the clutch lever. The mb will roll freely back and forth whether or not the clutch is engaged. It stops rolling when I put tge spark plug in. I think its two different issues happening at the same tine
     
  6. HadesBike05

    HadesBike05 Member

    I believe it was just jammed. I completly removed the plate n cleaned out some chewed up bits in there then I reatached everything. There was a certain tension needed but after when I put the spark plug back in rolled the mb forward the clutch engages and disengages well. (in case anyone else has this issue
     
    Timbone likes this.
  7. crassius

    crassius Well-Known Member

    good, you should read about adjusting cable & clutch to get that tension just right
     
  8. HadesBike05

    HadesBike05 Member

    I have been, n very enlightening. And I have confirmed spark, but the engine just wont start up. There is some air in the fuel line n when I press the primer on the carb the top half goes dry but the bottom half still has fuel. Im not sure if the fuel is even getting to the motor.
    When I hit the primer sometimes fuel leaks out of the carb.
    Should I dissemble and reassemble the carb? When I pull the throttle it doesnt seem to respond at all. If it is mounted wrong how will I know ehen I have it right?
    Thanks for any tips.
     
  9. crassius

    crassius Well-Known Member

    fuel in line usually has air in it - if it moves when tickler button is pushed, it is OK

    twisting throttle should move carb slide easily and letting it down should make a little clicking sound when slide hits bottom
     
  10. HadesBike05

    HadesBike05 Member

    Oh. Mine does not do that. I'll try adjusting it now. I twist n it moves the line a little bit but theres definetly no sound.
     
  11. HadesBike05

    HadesBike05 Member

    Well I fixed my throttle. The cable now goes up and down n I tried starting again n still no go. Im starting to think that even though I see a spark when I test the plug outside of the engine the cdi may be faulty. How can i tell without a voltmeter?
     
  12. HadesBike05

    HadesBike05 Member

    Fuel has begun to leak out if the muffler so it must be getting into the engine
     
  13. crassius

    crassius Well-Known Member

    that may mean that your motor is full of fuel - you may have to pedal quite a bit to blow it all out to get it to start - it then may take a few minutes to run well even after it fires
     
  14. HadesBike05

    HadesBike05 Member

    Could be be. Its just isolated drips though not a steady flow or steady drips. I tried over and over to get it going but its not starting up. A buddy of mine that is a mechanic confirmed that the fuel was getting were it needed to be n he tried starting it too but it just turns over n then nothing. I tried a few times twisting the throttle n there was a slight change in the sound of the popping but it never actually starts. Maybe its too much compresion. Theres another thread about troubleshooting that suggests testing the electricals with a .07 gap to replicate the environment of the spark under pressure so im going to check that next. Im hoping I dont have a faulty cdi but that may be it. Or im in way over my head lmao
     
  15. HadesBike05

    HadesBike05 Member

    If the engine pops when the spark plug is out and you roll the bike does that confirm compression?
     
  16. Nanonevol

    Nanonevol Member

    What makes you think you have too much compresssion?
     
  17. HadesBike05

    HadesBike05 Member

    Too much compression for the spark. Im starting to think the electricals are weak. Mainly because at first I couldnt get the bike to roll at all when the spark plug was in. When I let the clutch go it will roll and pop almost sounding like its on then stop hard and I am unable to pedal further. Is that compression or is my clutch adjusted wrong. Im not sure if I should tighten or loosen the flower nut
     
  18. crassius

    crassius Well-Known Member

    a compression gauge is only good way to confirm compression - too little won;t run - too much usually mean motor full of fuel - gauge can be borrowed free at many auto parts stores
     
  19. butre

    butre Well-Known Member

    quick lesson on compression ratios since from what I gather most here don't know much about it

    compression is supposed to be ambient air pressure * compression ratio (more on that later). so for example at sea level a compression ratio of 10:1 would be 147 PSI. you said in your intro that you're from south texas, so figuring you're at 500 feet (14.44 PSI) with the straight plug head (11 cc) on a 66cc that's about 86 PSI, with a slant head closer to 105, with a 7cc billet head around 135, a 6cc billet head is 158, a 5.3 is 179, and anything smaller is weirdo with a race bike territory that most vendors don't sell because they know the average consumer won't know where to buy race gas and will blame it on the vendor when the detonation they didn't notice blows a hole in the piston

    and then there's me, the weirdo with a race bike who knows where to get race gas. I'm running a shaved down fred head with a 4.8cc combustion chamber on a 69cc factory stroker, and since I'm at sea level I'm running a theoretical 211.68 PSI compression.

    now it's time to tell you to ignore everything I said completely, because it's all used static compression ratios when dynamic is what really matters.

    I assume you know what static compression ratio is, but if not it's the ratio between the volume of your cylinder and the volume of your cylinder head. dynamic compression ratio is a little more complicated, it's your static compression ratio minus the compressible fluid lost out of your ports or past your rings or head gasket if they're not sealing.

    people don't realize that the reason expansion chambers work so well is because they effectively increase the dynamic compression closer to the usually very high theoretical compression through a particular RPM band by shoving what compressible fluid gets lost out the ports on the compression stroke back in.

    dynamic compression ratio is always way lower than static. I would never be able to get away with my 14.4:1 compression ratio in a 4 stroke gasoline engine, 14.4:1 is on the low end of what you see in diesel engines.

    the easy way to find your dynamic compression ratio is to measure your stroke minus however far the exhaust port is opened. so my actual dynamic compression ratio is around 8.95:1, which in a 4 stroke would equate to 131.6 PSI.

    then after that crankcase compression throws another wrench into the system and I cannot remember how to calculate at this point because I never bother calculating dynamic compression.

    now I told you all this to maybe save you a few bucks on a compression tester because in this case if it's lower than calculated it doesn't matter, it still eliminates your compression too strong for the spark theory. if your compression tests or calculates at less than 197.4 PSI then either the ignition system is actually broken or something else is wrong. you know the drill for checking the ignition, spark plug in hand with the threads touching a fin on the motor. if it doesn't light you up something is dead between the magnet and your hand.

    instead of buying a compression tester right off the bat, because compression isn't your issue, buy a multimeter. as much as I like my $300 fluke, the $6 one from harbor freight does the job. they usually have a coupon for a free one with any purchase going around too. maybe you can get one when you buy the compression tester, that would work fine
     
    Last edited: Apr 7, 2016
  20. HadesBike05

    HadesBike05 Member

    Im sorry if I was unclear. I do not think my compression is abnormally great I believe my electricals are weak based on another thread on non starting that stated it is easier to get a spark when the plug is out of the engine then it is for a spark to be created under compression. I have confirmed the fuel is getting into the engine n I am still fiddling with the clutch n carb to try and get it working. When I emailed the distributor they agreed to send me a new cdi so it could mean otger people have had a similar issue or they dont want to bother argueing the point. Either way that could be a back up to an otherwise bumming experience
     
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