Sluggish Then Dead 80 cc Motor

Discussion in '2-Stroke Engines' started by wrightmor, May 30, 2010.

  1. wrightmor

    wrightmor Member

    I am searching to find problem similar to mine. My bike was running just great and I was riding it every day. I had a little problem with the plug wire coming out of the little black box. The last time i rode, it came out three times. I super glued it. I also had to refuel. I poured 4 oz of oil (same oil I used in the first gallon that worked so great). Gave bike first run after these two things complete and bike was sluggish. had to work throttle back forrth to get engine running again at full speed. Finally bike completely quit. Looks like paint pealing off my muffler (this may not be new- I just noticed it after my last infamous ride. Could my oil not mixed enough with gas and my motor is burned up? Or could super glue be preventing good contact. Of course I didn't actually apply glue to end of cable but to sides where it was going into the hole. Somebody please tell me I haven't burned up my motor. I love this bike. It is the same motor featued on (80cc).

  2. AussieSteve

    AussieSteve Active Member

    I'd suggest that you cut 1cm off the end of the plug lead, then screw it firmly back into the CDI.
    It sounds like you're just pushing it in.
    (There's a screw thread in the CDI, so the HT lead must be screwed in, not pushed in.)

    Regarding 4oz of oil, was that in a gallon or a tankful?
    What sort of oil?
    And how many ounces are there in a gallon? (I only know metric.)

    I'm glad you started a new thread on this subject. When you posted in the other thread I was going to suggest that.
    You'll get more responses this way.
  3. wrightmor

    wrightmor Member

    regarding plug wire and ounces in gallon

    I'll have to try that trim on the plug wire. If you see the first or second post I made, when I put this bike together I put the carb together wrong and when I started the motor it was at full throttle. Panic struck and all I knew to do at the time was to yank that plug wire. I had to walk back later and find it. I put it back together, but never screwed it and never had prob until now.

    that's 4 oz to gallon. (128 oz in one gallon). The breakin for the first gallon was six. I went through that and now have gone through the second gallon of 4 oz mixture and just had a ball riding all over the place. Now this third gallon, the very first ride and it's caput. I sure hope it's nothing major.

    I so much appreciate your kind response and suggestion. Will try tomorrow. now it is almost 10 p.m. and raining cats and dogs here in central Florida.
  4. AussieSteve

    AussieSteve Active Member

    Hopefully that's all it is. If it still won't run, try a new plug.

    Those fuel/oil ratios equate to 21:1 during run-in, then 32:1 since then. That should be OK, although personally, I use 20:1. These engines are poorly manufactured and the higher oil ratio helps the piston ring to cylinder wall seal.

    (The factory recommendation for my ZBox 66cc engine was 16:1 during break-in, then 20:1 thereafter. I've stuck to that.)

    Let us know how you go.
    Last edited: May 30, 2010
  5. GearNut

    GearNut Active Member

  6. AussieSteve

    AussieSteve Active Member

    Yeah, I'm glad Australia changed from imperial to metric, (when I was about 12 yo).
    Much more logical and simple to learn.

    By the way, you shouldn't need a chart - it takes 2 seconds with a calculator.

    Was that the recommended ratio with your kit?
  7. wrightmor

    wrightmor Member


    25:1 was recommended after the breakin. I did the math. That does work out to the directions of the kit (4 oz per gallon of gas). I have undid my super glue job and screwed the wire into the block as you recommended, Steve. But still no go. The spark plug wire, itself, is still suspect in my mind. It is just resting on top of the spark plug. It doesn't snap and lock on. But seems like I still should get some kind of performance out of it, even if erratic. I actually tried to hold it down tighter while I released the clutch (not easy) but got not even a tingle of sting. That didn't make sense to me. Should I replace the plug wire, if it is not locking on or should that make that much of a diffence since gravity is holding it loosely onto the top of plug. Today, being Memorial Day not a good time to go shopping. It was riding just great with capital G last week. I hate this. Would plug be suspect if it was doing so good just last week? not even a sputter.
  8. GearNut

    GearNut Active Member

    I never have had an owner's manual to read a recommended break in ratio.
    25:1 has always worked well for me in the past, regardless of the manufacturer.
  9. AussieSteve

    AussieSteve Active Member

    GearNut, anything from 15:1 to 32:1 will work well, as you put it, but the less oil, the shorter will be the engine's life.
    Running 20:1, my plug is always light tan with no deposits.
    What do you run after break-in?

    wrightmor, you need to replace that lead, or at least the cap, so that it attaches properly to the spark plug. Gravity is not enough.
    Having said that, if you held it on firmly and still didn't get a spark, there's possibly something else going on.
    I'd recommend that you fix the plug lead properly, then remove the plug and fit it to the lead and lay it on the head with the plug body touching the fins, then spin over the engine and look for spark.
  10. wrightmor

    wrightmor Member

    after breakin I am running as suggested in the instructions that came with motor, 4 oz per gallon of gas. Prior to breakin it was 6 oz to gallon.
    It has been running so good. I went through one gallon of the pre-breakin which the manual suggested would be enough. Then the second gallon I just finished last week of 4 oz to gallon with no problems. Now when I am starting on the third gallon or 4 oz to gallon
    I have this. Don't really know if the gas ratio is even coming into play here. I did run pretty low before refueling. Maybe I got some kind of trash in the line (optimistic thinking, I guess).
    I will replace the plug wire and maybe even the plug tomorrow (though like I said, I have had no problems with plug last week - none. There is a place local here called Mopeds and More that sells motorized bikes. Could be I can get my parts there. Maybe even have them look at the bike if this doesn't get it. Just checked net. I can replace that exact motor for little over $100. I know, I know... you get what you pay for but I have had so much fun with this motor as cheap as it came (and that is with entire kit price!)
    I will try that plug on the fins of motor thing. I suppose I can turn the motor with the bike in neutral (clutch pulled in??) Otherwise I can't test it for spark.
  11. AussieSteve

    AussieSteve Active Member

    Sorry, we got off-track with the oil ratio. That is definitely not the problem.
    Stick with your current ratio, it's fine.

    Best way to test for spark is with the clutch out. Lay the plug on the head as described, then lift the rear of the bike and spin the wheel forwards.
    (You might need a helper. A centre-stand is great for this, or if you have a side-stand you can lean the bike over so that the wheel is off the ground.)

    Otherwise, with the clutch disengaged, (pulled in), remove the magneto cover and use a drill with a socket to spin the motor.

    Don't be too concerned, it won't be too hard to sort this out.
    Keep us informed.
  12. wrightmor

    wrightmor Member

    second reply here, lost my post

    Just a quick note of sincere thanks for all your helpful suggestions. As you probably have been able to discern, I am not a mechanic nor do I even play one on tv. I am just a guy that got lucky and managed to put my bike together and It worked - too good to start with. Went from stand still to a little dot in wife's vision as she was going to photo my maiden ride. Carb part put in backward. 0 to 35 in 5 seconds.

    I do intend to replace plug and cable assembly just as soon as I can purchase the parts this week. Hope I can find them at the local Mopeds and More shop. Might have to mailorder.
  13. AussieSteve

    AussieSteve Active Member

    No worries, glad to help. I have heaps of spare time these days.

    Try your local mower shop as well. The cap is irrelevant - any type will fit. The main thing is to get a plug lead the right size for the CDI. I think it's 7mm, but I'd advise you to measure your's.
    Note that some plug caps need the little screw cap on the plug, whereas with others such as the standard cap the plug's screw-cap must be removed.
  14. wrightmor

    wrightmor Member

    I'm back on the road.

    The good news is the bike is running. I replaced the spark plug cap. It now buttons down and snaps to lock on to top of plug.

    The bad news is it's idling a bit fast and still skips on the road. The idle is rough.
    Also, I think somehow I have messed my muffler up. seems louder now. The plug looked like it was very hot at the base of the porcelain and maybe a little damp or at least discolored

    But I had a fairly long ride. Just not sure why the idle is so rough. nor how I could have messed up my muffler.

    Another good news story, though, is I think I fixed a squeak I've had in the clutch ever since the original install. The clutch engaged even while I was rolling the bike (motor not running) to garage. So I pulled out pliers and readjusted clutch cable. did one more quick ride and no squeak.
  15. AussieSteve

    AussieSteve Active Member

    Check that the screw in the end of your muffler is tight. Also check the exhaust mounting nuts for tightness and the exhaust gasket visibly for signs of leaks. That would make it louder.

    It sounds like your fuel/air mixture is a bit lean. That would cause a fast, rough idle and overheating.
    First, what colour is the spark plug? It should be a tan colour. Black and oily indicates a rich mixture and grey or whitish indicates a lean mix.
    If it is lean, the most common cause is an air leak where the carb attaches to the inlet tube. Some sealant in the joint during assembly will fix that. You only need a tiny bit. Better still is to get an 'O' ring that just fits into the carb opening such that when the carb is pushed onto the intake, the end of the inlet seals against the 'O' ring. Best of all is to buy an alloy inlet tube and file an 'O' ring groove as close to the end as possible. That's what I did. See NT carby/inlet leaks - a reliable solution

    Have you adjusted the idle screw to try to slow the idle? (That's the screw on the LHS of the carb.) Screw it out to decrease the idle or in to increase.
    Did you fit a new spark plug? (NGK B6HS)
  16. wrightmor

    wrightmor Member

    tried to replace plug but could not find proper equivalent. He sold me a little midget type that is totally swallowed up by the cap. I bought it in case the new cap was not sufficient to get me started. When bike started w/o the new plug, I decided to wait and find a plug closer to recommended. The vendor said the little plug works great on motor bikes but still I am skeptical. May have to order the plug.

    I hate to sound dumb but color of plug? You did mean to take the plug out and look at gap area, right? I can see discoloration aound the bottom of porcelain w/o taking it out.

    Muffler screw. I looked up at bottom of muffler and saw the "guts" of the apparatus surrounded or encased in the hollow shell of the muffler body. Dead center of this 'gut' was a screw hole (I can see threads) but no screw. Would putting a screw in make a difference or was the missing (if there is a missing) screw holding something else together. I told you I'm not a mechanic.

    I haven't tried adjusting the carb screw yet. I did that when I first got the bike because I didn't have idle at all. Never got the idle that way. turning made no diff. I called the place I bought it from and he suggested adjusting the top of the carb where the cable goes in (to raise or lower it thereby causing more or less gas to carb). That got me my idle and it has worked great for couple of years now. I will try adjusting the screw this weekend.

    Carb reseat? Should I try this your were saying. If so I'll prob go the permatex route at least this first time.
  17. AussieSteve

    AussieSteve Active Member

    These things are a real learning curve, aren't they?

    You shouldn't need to order in a spark plug.
    Be skeptical - the vendor doesn't know what he's talking about. All motorbikes take different plugs, designed for different amounts of heat transfer and a particular thread length and overall reach, among other things.
    The best suitable plug for these engines is an NGK B6HS. They're sold by most auto-accessory shops.

    Yep, when I refer to plug colour, I'm talking about the colour in the gap area and on the porcelain tip, when the plug is removed. There's a pic showing the right plug colour several posts into this thread,
    NT Carb Tuning Basics , as well as a little more info on NT carbs.

    There are a couple of different muffler types. Mine has an end-cap that is held on by that screw. With either type, if the screw is missing it will be noisier because some exhaust gas bypasses the baffles and escapes directly out that hole. The end-cap and would fall out if the screw fell out of mine.

    The idle screw is the best way to set the idle, rather than by tightening the cable. The problem with using the cable is that it's always under pressure and so the idle will rise when you turn the handlebars. It's best to have about 2-3mm slack in the throttle cable, to allow for this.

    Virtually all[i/] NT carbs leak at the point where they join to the intake tube, making them hard to tune. Any sealing method is OK.

    I think I've covered everything.
    Have fun.
  18. Your muffler is missing the end cap and the screw that holds it on, it is much louder without this cap.
  19. AussieSteve

    AussieSteve Active Member

    You're most probably right. I pictured only the screw missing, but that wouldn't make it very much louder. And as I said, mine would fall apart almost immediately without the screw.

    wrightmor, the end cap, (which includes a short length of pipe that extends back into the muffler), is probably somewhere by the side of the road where you were riding when it got louder. Most likely flattened. You'll probably need to buy a new muffler in this case.
  20. wrightmor

    wrightmor Member

    muffler gone

    Y'all are both right. Muffler is shot. I have ridden several passes over my roads and didn't see it.
    I did get new plug. Made no difference. It is drivable. Just sluggish, especially when I try to throttle more. When I throttle it tends to cut back. If I slow down on throttle then re-throttle it will somtimes pick up the speed like it should but that doesn't last.
    I noticed when I got home from last ride there was a constant stream of bubbles going up my clear plastic gas line. the bubbles lasted about 4-5 minutes. When it stopped I wiggled the line down toward the carb and more bubbles appeared. Maybe this is normal. I just never noticed it before. I think when I wiggled it it let air in from the bottom of the tube where it slides onto the carb.

    Am I doing damage to bike riding it when it is responding like this? It rides ok and rides fairly fast but is slightly erratic. I tried adjusting the screw for idle. It works but I noticed when I had it about right (so I thot) and tried to pull up the choke to kill the motor, the choke actually served to reve motor.

    I am getting a new muffler soon. Should I try to re-fuel with fresh gas and oil mixture?