Help!! - No spark on 48cc motor (brand new)

Discussion in '2-Stroke Engines' started by Watcher05, Jan 24, 2008.

  1. Watcher05

    Watcher05 Member

    HELP! :-/

    I have purchased a Chinese 48cc motor. Have fitted motor but getting NO spark. I can hold the plug and sometimes get a mild pulse/current but nothing to boot me off the bike.

    Have tested magneto: 363 ohms

    Have tested CDI unite black wire to plug lead/cap: 2.3 (testing at 200k).
    I've even held the blue and black wire coming out of motor/magneto and only a light pulsing.

    Any ideas before I start replacing parts etc. I'm assuming that to get a spark, it only takes a bit of speed on the bike to produce something (pedaling around the back yard while clutch is engaged).

    Thanks heaps.
    Last edited by a moderator: Dec 15, 2015

  2. Papasaun

    Papasaun Guest

    I would start by checking that the connections for the cdi are in fact good and tight, (this includes the spark plug lead at the cdi). That the spark plug does indeed fit into the spark plug boot securely. If you have already wired in the kill switch, you might consider taking it out of the system for the time being (until after testing). Other than that,,,read, read, read, all the searched posts on ,,, no spark or,,, wont start.

  3. ibdennyak

    ibdennyak Guest

    Sounds like a mag problem to me. On mine, they work at about 260-280 ohms. Past 300, and I get a weak or intermitent spark. I have 4 of them laying around right now that read 350 plus. In my case, I think it is moisture. When I get a new one it works fine, until a ride in a drenching downpour. After I shut it off, it will never start again. (I live in a rainforest, so moisture is unavoidable) My next plan is to add varnish, or repot the thing somehow when it is new. I believe Dax has a couple posts with specs on it.

    If you find a different solution, or figure out why they do this....keep us posted.
  4. Watcher05

    Watcher05 Member

    It is reading at 363 ohms & have phoned zbox australia and he's under the impression that it can only be the CDI box. He said its unusal but sometimes they can fail. But won't receive it until late next week to see if it does acutally fix the problem. :confused:
  5. ibdennyak

    ibdennyak Guest

    Yeah, on mine it seems like it takes the cdi with it when the mag is weak. I have three of them in the same box as the 4 mags. :smile: Some day I will have to take one apart to see what it in to understand how they work. When you checked your cdi did you notice the resistance slowly rising like a capacitor charging up?
  6. Watcher05

    Watcher05 Member

    As regards to checking the CDI; it just reads as 2.3, as I'm not exactly sure what the reading should be?? But the magneto was coming up as good! Not sure if a reading of 363ohms still means that the magneto can still play up??

    Also, I've managed to get some spark from it but seems to be intermittent.

    I've tried to eliminate if its a fuel problem by using wd40 but it still won't ignite.

    If the replacement CDI unit fails to fix the problem, I'll be sending the motor back. It seems like alot work, especially for a brand new motor!!
  7. Watcher05

    Watcher05 Member


    I have got the motor going, although its been a slow and laborious process. But now it has no power what so ever going up a very slight incline!! When I give it throttle it seems very sluggish.

    I've searched the forums for info but nothing obvious. However, I've cleaned carby out; adjusted needle up and down but still now power. Unless its still this electrical/CDI problem!!

    I'm not asking for some sort of high powered output, but I was advised before I bought the kit that it would go up hills reasonably easy (within reason). Certainly not doing that at the moment.

    Please, any feedback would be helpful.

    I didn't think the kits would be this much work :(
    Last edited: Jan 27, 2008
  8. Scottm

    Scottm Guest

    You are still in break in period. Be patient, it will gain power as it goes. Some of us here have changed spark plug wires to a higer grade copper core wire. I noticed the difference on my motor.

    Denny, I think I still have the CDI that melted on my muffler.( I'm a pack rat) . I suppose I could cut it open and post pics or mail it to you.
  9. alesterfeind

    alesterfeind Guest

    Also, check your clutch adjustment. Even though it might feel like it's engaging and disengaging correctly, it seems like it has to be in just the right spot for the engine to fire. I had the same problem with mine when I first put it on, and moving the clutch slightly seemed to do the trick.
  10. fetor56

    fetor56 Guest

    You said u got the motor's too early isn't it to have your replacement CDI.
    Warren from ZBOX is good and he'll stick by u but at this stage i think your lack of power is just cos it's new and TIGHT.It takes around 300Km to loosen up properly.
    You've adjusted your needle and i'm assuming you've o-ringed the carby and trimmed your intake/exhaust gaskets.
  11. Watcher05

    Watcher05 Member

    Thanks for the great replies!

    That's right fetor56, I haven't received the CDI yet but I was very persistent and being a long weekend and all I just kept adjusting things, although the spark was very intermittent. I did take strip the spark plug cap back re-adjusted the gap on plug to .30 (is this right??) and it eventually started firing after a lot of pedaling around the back yard.

    I've also adjusted needle up and down & have left it back on second notch (the way it came). Cleaned carby and placed inline petrol filter on.

    As far as putting and o-ring in and trimming intake/exhaust, I haven't. Didn't realise this was necessary!! As far as the exhaust manifold goes it blew itself out, so I need to replace it! Please explain about trimming gaskets (will do a search).

    Also, I'm running it at 16.1 fuel mix - is this too rich? Have read that 20:1 would be fine for breakin period?

    thanks so much for the replies.

    NB: to moderators. I know that we’re encouraged to search the forums to get info first. Believe me, I’ve searched and searched and have picked up some great info but I suppose that there are so many variables when a bike won’t start, that it won’t just be in the one spot. So apologies if this info is being repeated.
    Last edited: Jan 27, 2008
  12. fetor56

    fetor56 Guest

    I use SP gap .025" or .63mm.
    Here is the thread about o-ringing your's important:

    With ZBOX engines the actual engines intake/exhaust ports are oval while the carby intake manifold is round and so is the exhaust manifold.
    Both gaskets are round but they seal against an oval surface so u need to get a Stanley knife and gently trim them'll see what i mean.
    Block both ports with rag if your going to do this so u won't get any gasket material inside the engine.
    I also got a dremel and made the carby intake manifold and exhaust manifold oval shaped but that's not absolutely necessary....the main thing is to trim those oversized gaskets cos they restrict fuel vapor flow to the engine and exhaust gasses flow from the engine.
  13. Scottm

    Scottm Guest

    I admire you

    I'd stick with manufacturer's suggested fuel ratio for your engine and NO synthetics until the rings have seated. Don't worry after a while all the kinks will be worked out and you will be infinitely wiser about your motor and your bike. It's a pain now it seems, but it's part of the whole experience. Bike and rider bonding. MBc is the best tool in the tool box.
    And when people ask you can honestly say "Yeah! I built it".:cool:
    I admire your stick to it attitude. Don't over complicate things.
    You and Fetor will have to get togther soon and go ridin and tinker with each other's bikes.
    Keep up the good work.
  14. fetor56

    fetor56 Guest

    Not sure about "soon" Scott...Watcher is in Northern New South Wales(dunno exactly where) while i'm in Adelaide,South Australia.I'm guessing that's a distance of approx 1300Mls so i'll need more than a cut-lunch to drop over his place.
    Who knows,perhaps one day we'll meet...perhaps one day i'll meet some of my Northern Hemisphere friends. :)
  15. Scottm

    Scottm Guest

    Oops, I missed a few sparks in my cyclinder. I saw Australia and forgot about the NSW. That would like me riding from here to MBc central in Washington, except you'd have to cross the water.
    Sorry to go OT and I appreciate the geography lesson. Perhaps and equator rally in the pacific. We could rent a cruise line and ride around the deck as if it were a board track.
  16. Dockspa1

    Dockspa1 Guest

    Definately seal your exhaust pipe. 2 strokes require a little back pressure in order to run properly. I agree that you need to back your SP gap down to a max of .025.
    They really are skimpy on the copper when it comes to the pick up coil so if you can get your spark plug to a finer gap it should help. Mine runs good at about .022.
    Just some thoughts.
  17. Watcher05

    Watcher05 Member

    Okay, I suppose I should give a bit of an update since my last post.

    Yes, I did get my motor going......eventually. I'm not sure if I mentioned but when I previously had it going, I did blow the exhaust gasket. Fixed it and the next day do you think that I could get the motor going? No! :???:

    Believing that it was an intermittent electrical issue (which I think the original problem was) kept trying to get the little beast started. I was all out of ideas until I thought I'd take the exhaust right off. Low and behold, I'd forgot to cut the hole out of the freakin gasket!!!!! I hope I didn't blow any other gaskets in the process but she seems to be purring along now. Not sure why on earth I didn't but just obviously forgot. Doh! That's not to mention to get it started originally did take a fair bit of effort and I think it was a dodgy spark cap. Stripped it back and had some sort of success. :cool:

    I'm feeling a little bit sheepish and wasn't going to tell you guys but thought it maybe worth something for others starting out: check and recheck! :rolleyes:
    Last edited by a moderator: Dec 15, 2015
  18. fetor56

    fetor56 Guest

    You got it, "check and recheck!" ...and while your standing around sipping your coffee and smoking cigs recheck again.
    Anyways your upwardly mobile.....GOOD. :)
  19. Watcher05

    Watcher05 Member

    Hey Fetor, sent you a message.

  20. Scottm

    Scottm Guest