Electrical connections are fine, but spark is weak.

Discussion in 'Motorized Bicycle Trouble Shooting' started by ballinchestr, May 20, 2014.

  1. ballinchestr

    ballinchestr Member

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    My kit is new, and the engine's never been run. I wasn't getting spark, so I replaced the stock spark plug with a Champion one. I still didn't see a spark, but this time, I just touched the end of the plug while cranking, and it gave me some good consistent shocks. The only thing is that I can't see or hear them, so I don't think they could ignite the fuel-air mixture.
    I already disconnected the kill switch, and trimmed and reconnected the spark plug wire from the cdi. What's causing the lack of power?
     
  2. crassius

    crassius Well-Known Member

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    sometimes the gearing on a bike will make the spark seem weak just because you aren't turning the motor fast enough (usually happens with one speed cruisers)

    have you tried riding it fast to get it to start?
     
  3. 2door

    2door Moderator
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    First question would be, how fast are you rotating the crankshaft? In other words are you pedaling the bike (rear wheel) up to at least 10 mph? Just slowly rotating the crankshaft might produce enough current that you can feel it but not enough to generate a sufficient spark.

    Raise the rear wheel off the floor, clutch engaged and pedal or spin the rear wheel. You'll want the spark plug resting firmly against the engine and watch for a spark at the plug's electrode end. These little magnetos don't produce a spark like you'll see on an automotive engine so unless they are spun over faster you might not see a visible spark.

    Tom
     
  4. CTripps

    CTripps Active Member

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    You might also want to grab a large towel (you know where your towel is, don't you?) or something similar and drape it over the top bar to make a 'tent' over the motor.. it's often easier to see the spark in a shaded/shadowy area.
     
  5. crassius

    crassius Well-Known Member

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    sure, keep it right next to my 'no tea'
     
  6. CTripps

    CTripps Active Member

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    Excellent. Then if needed, no doubt anyone you encounter will happily lend you anything else you may need or have misplaced in your travels. ;)
     
  7. ballinchestr

    ballinchestr Member

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    Okay, it was the CDI, I replaced it, and now there's a good, consistent spark. The only problem is it won't start. When I ride it, I hear a couple thuds or pops from the engine, as if about to start, but they stop after about 60 feet of riding. I drain the carb after each try. Should I hit it with some good ole starting fluid?

    Edit: Oh yeah, when I put it away, I noticed a drop of gasoline out of the muffler, what does that mean?
     
  8. crassius

    crassius Well-Known Member

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    first thought would be that the motor is full of fuel - try riding with spark plug out to blow it out inside

    second thought would be clogged muffler - try loosening it about 1/4 inch at the mounting studs
     
  9. CTripps

    CTripps Active Member

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    Pull the plug, pedal up to speed, take (and hold) a deep breath and drop the clutch. If the engine's flooded, you'll surround yourself in a cloud of fuel.. resume breathing when you come out the other side, and get ready to do some laundry. (I was nearly handed my bathrobe while on the porch last time I did that.) ;)
     
  10. ballinchestr

    ballinchestr Member

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    thanks everyone, got it running today (aw yiss). Any way to reduce muffler vibration? the thing looks like the welds will break after an hour of riding
     
  11. crassius

    crassius Well-Known Member

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    if you don't have the muffler hanger on it tight, it will also rip the studs out of your motor - if your hanger isn't working, make a stronger one
     
  12. ballinchestr

    ballinchestr Member

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    I wasn't aware of a hanger... maybe it wasn't included?
    How can I make one? I have some scrap aluminum
     
  13. crassius

    crassius Well-Known Member

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    should have been included, but kind of crappy

    you can wrap a length of coat hanger wire around the outlet of the muffler, then bring it around the bottom of frame and back to muffler outlet - then stick a screwdriver between the two wires and twist them until tight - check tension after first several rides until it stays tight

    you want it to hold the weight without pulling hard on the studs
     
  14. CTripps

    CTripps Active Member

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    The latest kits I'm working from include a flat strip of metal with a hole drilled in each end.. as it's the last thing in the box, I have to assume that's what it's for. I've also used the black metal strapping that is used to hold product on pallets/skids for shipping to make an exhaust hanger. If I remember correctly (my worksheet is up in the garage), the diameter of the 'stock' muffler is 6.25".. plus 1/2" to make a tab to drill a hole through. You'll need to measure the diameter of your down tube, and how far from the tube the muffler is.

    So, for the one I just did up yesterday, here's how it goes.... You'll need a strip of metal about 1/2" wide and close to 14" long (the ones I'm playing with now are 13.75" long). [Yeah, I'm going to over-explain it.. I'm bad for that ;)]

    • Mark 1/2" from the end (let's call it muffler end)
    • Mark 6.25" from the first mark
    • From the other end (frame end) mark 1/2"
    • Measure the diameter of the frame tube and mark that off
    • In both 1/2" tabs, drill a hole 3/16" or a hair bigger than the size bolt going through it (centered)
    • Just past the marks for tube and muffler diameter, make 2 more holes, centered - these need to line up with the holes at the end of the strap.
    • Bend the strap to a right angle at each mark (keep the same side of the strip facing you, all bends in the same direction)
    • Wrap around and fasten together on the frame first, then the muffler.
     
  15. ballinchestr

    ballinchestr Member

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    I found that metal piece with the holes. I bent it around the 'neck' part of the pipe, right before the actual 'barrel'. I wasn't sure where to go from there, so I tried cable ties. I drove it around a bit, and it didn't melt. Should I keep it on, or try something with a little more heat tolerance?
     
  16. crassius

    crassius Well-Known Member

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    that piece you found *should* attach to a round piece that fits around the muffler - can't find a pic right now, but there are two types one looks like a lollipop & other looks like a barbell
     
  17. ballinchestr

    ballinchestr Member

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    There isn't any more hardware in the kit. Oh well, I'll see if it will hold up.
     
  18. crassius

    crassius Well-Known Member

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    closer to the bottom is better that near the top
     
  19. BobbyT

    BobbyT Member

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    You should find a couple of bolt's for your hanger. Stock mufflers need all the help they can get. It can be dangerous going back to get a hot peice of metal in the middle of the road..xx.
     
  20. CTripps

    CTripps Active Member

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    The cable ties are probably going to melt (at least the one closest to the exhaust will).. best bet is to grab a couple of bolts, nuts etc to hold it together with. You should support the muffler itself, around 2/3rds to 3/4's of the way to the end of it is usually good.

    Next time I bend one from flat stock I'll try to remember to take pics.

    The one on the red frame is the flat strip I bent to shape a couple of days ago, the one with the spring with loops made from metal strapping is on my beast (and it has held solidly for over 2 years like that).
     

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