No spark

Discussion in 'Motorized Bicycle Trouble Shooting' started by George Tirebiter, Jun 22, 2015.

  1. George Tirebiter

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    I still can't get a spark after replacing the spark plug. These are the readings I get with the multi-tester: at 200k

    Mag test - Black to White =.3
    Blue to white = 0

    Blue+ to Black- =.3
    Black+ to Blue- =.3

    CDI test- Spark plug+ to Blue- = 133
    Spark plug to Black =7.2


    These readings imply a problem. Seems like both Mag and CDI might be bad? Any suggestions are much appreciated.
    George
     
  2. crassius

    crassius Well-Known Member

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    coil attached to blue wire is out (that one makes your spark) - check for 2 tiny wires at top of coil & see if both are soldered well to the armature
     
  3. Paddy

    Paddy New Member

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    Hi the coil on your magneto should be reading around 320-350 ohms so this is either a problem with the soldering as said above (Had this problem on my own bike) or a dodgey coil which is higley unlikely. Check the gasket for the cover on the magneto aswell cause if its allowing water in it will short out whats being produced by the magneto. Use some gasket maker when your putting the cover on aswell.
     
  4. George Tirebiter

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    Paddy, thanks for the reply. I must have got some false readings on my meter because it starts right up even though I couldn't seem to get a spark. Maybe just not enough RPM's?
    George
     
  5. George Tirebiter

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  6. Paddy

    Paddy New Member

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    Thats good news! You should be able to get a faint spark even when you rotate the wheel by hand when its off the ground. Did you earth the spark plug on the head? Maybe the spark plug wasnt earthing properly on the head if its painted or just dirty if you did try to earth it or maybe the room was to bright.
     
  7. Kioshk

    Kioshk Active Member

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    Paddy's right; RPMs ain't a problem. When I was first familiarizing myself with these engines, I used to remove the spark-plug, reconnect it to the CDI, and roll the bike a few feet in gear. This relieves compression so you can roll the bike easily, and with the plug resting on top of the head, you can easily see the sparks in the shade. I have NEVER lost a CDI (although I thought I had a couple of times), but I HAVE gone through about a dozen magneto-coils in 3-years; they're VERY finicky about moisture. I've learned to seal the magneto-compartment properly, but I ALWAYS carry a spare coil in my kit. When one blows, I immediately reorder. You don't want to be 10-miles from home when your coil blows.
     
  8. George Tirebiter

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    Paddy, I think you just solved the mystery. The engine is painted black, so that might explain the lack of spark. Thanks again,
    George
     
  9. George Tirebiter

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  10. Paddy

    Paddy New Member

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    I have a black engine too george i think we both have a good taste for engines haha. Im glad its solved and your welcome!
     
  11. Jmichaelg21

    Jmichaelg21 New Member

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    If im using the wrong spark plug could that fry out the cdi and magneto also can someone explain what the specific readings should be for both magneto and cdi and what setting on a multimeter is to be used. So heres whats going on when i do the spark plug check i lay it on the carburetor throttle body since my engine is black. When i roll bike forward i get 2-4 good sparks then nothing this is all based around either the spark plug gap or tickering with the magneto try again same thing 2-4 good sparks then nothing. Also does anyone know what the gap should be set at for the spark plug the book says .6 - .7 mm what would that be on a feeler gauge?
     
  12. Slogger

    Slogger Member

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    J Michael
    No spark plug will fry your CDI unless it's shorted out, in which case you'd see no spark at all.
    The carburetor body may not be grounded well to the engine case. There is a gasket between it and the cylinder. It's grounded through the screws, but it's not a good place to pick up a ground. I'd scrape a little spot of paint off of the head to hold the plug against.

    The gap should be between .024 and .028 as is often recommended around here.

    You're seeing some sparks, even grounded to the carb, so I would guess your mag coil and CDI are probably ok. The mag coil being open or shorted you wouldn't see a single spark. CDI? um, not sure.
     
  13. Jmichaelg21

    Jmichaelg21 New Member

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    Update no spark at all no matter what i do just going to go to my guy get the parts for electrical and redo everything maybe some dust got in the mag housing through wire hole gonna use high temp silicone gasket maker on housing gasket and wire hole and upgrading to a better spark plug and cdi
     
  14. JoannaKeys

    JoannaKeys New Member

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    Hi Fellas! I could use a little of your expertise.

    My husband traded out some sign work last year for a Grubee Skyhawk GT-5 Rat 66cc mounted on a big beach cruiser that I have since swapped over to a smaller MB that I can actually touch the ground on. The guy he traded with put it together and only rode it once or twice so, so wasn't even broke in when I got it. (This is just to point out that the engine wasn't rode into the ground before I received it). Anyway, I broke it in according to Grubee instructions, have put around 500 miles on it; and, it has been running pretty well until last Tuesday.

    While at a stop, it died and I was unable to get it going again. When releasing the clutch there was only a very weak spark. I tried adjusting the clutch, cable and chain tension and still couldn't get it to go. Now, I don't even have any spark at all. I have compression, there is nothing wrong with the stock, 3 pt spark plug that the engine came with and inside the CDI MAG housing in clean, dry, grounded and, as far as I can tell without taking it apart, nothing has been melted.

    I don't know what else to look for. Any suggestions would be greatly appreciated. I'm having MB withdrawls. I miss my rides!
     
  15. Jmichaelg21

    Jmichaelg21 New Member

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    Try to find out what the readings should be for your cdi and mag on a multimeter im still pretty new but ive been through 2 cdi and 2 mags just upgraded to a high performance plug and dual boost bottle system replaced mag and cdi and now she fires right up but i know the first time i blew the mag was at stop light and bike just died would try to start but nothing replaced mag and was good as new but check the readings first check you tube if your unsure of how to check
     
  16. JoannaKeys

    JoannaKeys New Member

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    Thanks for that quick reply!

    I know that I need to get an ohm meter...and learn how to utilize it. My concern is that if I need a replacement, where will I find one? When I Google "Skyhawk GT-5 Rat CDI MAG" nothing matches what I have on my motor.
     
  17. crassius

    crassius Well-Known Member

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    my guess is that it is a super rat with the CDI & magneto all packed into the left side cover - try to google that & look at pics to see if that is it
     
  18. JoannaKeys

    JoannaKeys New Member

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    It must be the Super Rat because the CDI and Magneto is in the same housing together. I've tried every search term I can think of to no avail. This "CDI MAG", as Grubee calls it, is just not coming up in the search engine.

    I would certainly hate to have to buy an entire engine just because of one silly part. Could a different one be used instead?
     
  19. Davezilla

    Davezilla New Member

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    You can get super rat ignition parts from a few ebay sellers... I buy cylinders and a few other goodies from a seller named mzmiami and he carries Super Rat parts, I got a super rat bottom end a few months back and built it up for one of my bikes but not until I was sure I could get new ignition parts since these engines do have a rep for burning up the cdi units...
    This is the part you need to fix your bike... I would buy an extra as a spare too.... http://www.ebay.com/itm/MOTORIZED-BICYCLE-GT5-SR-SUPER-RAT-CDI-Coil-66-Cc-/281622700312

    Another tip would be to drill a hole over the center of the small fan on the mag rotor so the engine can pull fresh air into the cdi cover instead of swirling around the hot air that's trapped inside. Just a 3/8" to 1/2" hole in the cover plate right at the center of the small fan is enough to pull in plenty enough fresh air to keep the cdi cool, but that air needs to be able to go over the cdi so blocking off the little holes on the bottom of that cover and drilling a few (3 or 4) 3/16" holes at the front of the cover will direct the cooling air over the cdi unit and help keep it cool enough to survive.
     
  20. JoannaKeys

    JoannaKeys New Member

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    I found them. Thank you! I had a look a Grubee's website and found that MZ Miami is the only WD for Super Rat parts in the US.

    Based on your drilling advice, I'm guessing that the design failure is not in the CDI unit itself but rather the housing? If that is the case, would it be over kill to have a finned cover fabricated? Or, what about the heat shield material? I don't remember what it is called. I believe it is supposed to dampen the engine noise as well as protect from the heat created inside the housing.
     

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