Motor not engaging, new to this, PLEASE HELP

serrath · Mar 4, 2014

I purchased a used 80cc bike over the weekend. It was a complete impulse purchase - I went out to buy a regular mountain bike and this is what I came back with. The owner showed me how to worked and everything seemed fine on it; it started okay and all the parts seem to work.

Two days later and I try to start it and it doesn't start. I'm really at a loss to describe what's wrong because I don't know a lot about motors; I tried to google the problem myself but not knowing what the different parts are or where they're located, I can't seem to figure out how to troubleshoot or diagnose my problem sufficient to even ask how to fix it.

Basically, I can pedal to speed, i release the clutch and it sounds like it's starting (like the motor turns a couple of times) but then the engine dies. It does this every time I try to start it.

A couple of things I did when I first purchased it; I filled the tank with petrol (it was nearly empty when I bought it). Also, on my first ride, the back tire blew and I had to replace the tube but I think I got the back wheel on okay. Regardless, the day after I did these two things, it started fine (not even a hint of a problem), it's now the day after it worked great and it's not working.

Are there common things for me to check? People on these forums have suggested I check the sparkplug but I don't know where the sparkplug is located and all the DIY guides I can find online tell you what to look for on the sparkplug but not where it's located or how to remove it.

Is it possible it's flooded? I don't know what the symptoms are for flooding or if it would cause <this> problem (i.e., the engine seems to turn over a couple of time when the clutch is released and then stops) or a different problem. How would I diagnose the problem and fix it if this is what's wrong?

For the life of me I can't understand how this problem could just suddenly appear after a day a working fine. I assumed if it would stop working, it would have done so immediately after I changed things about it like the back wheel or adding fuel...

If you could help me get the bike running, I would be so thankful. I'm a pretty fast learner and I intend to get a good working understanding of engines through this, I just need a bit of an introduction as to what parts do what, what to check, and what could be wrong as a start.

serrath · Mar 4, 2014

I should mention, I can take pictures of anything on the bike if it'll help diagnose my problem; I really am interested in learning, I just need some help identifying specifically what parts we're talking about if anyone has a followup question

Theon · Mar 4, 2014

What Oil Mix did you use when you refueled it?
Which Carby does it have (anything written on it)?
Photos are helpful.
Checked for spark?
Have you tried draining the fuel bowl?
I belive there are some problem solving threads here already, have you looked through them?

serrath · Mar 4, 2014

Oil mix was just regular petrol at the gas station. I was told to fill it with regular unleaded, does it require a special mixture?

I don't know what a carby is; it's a z box? engine; it has a "Z" on the side

Don't know how to check for spark; all the guides I've read concerning checking the spark plug don't mention where it is and how to extract it

Is the fuel bowl the fuel tank or something else? If you tell me how, that'll be the first thing I check

YES I've had a long look at several threads but I can't make sense of them without the basic knowledge

they all assume I know the names of the parts and I don't; feeling kinda lost

Theon · Mar 4, 2014

Mate, you got a lot to learn about 2 strokes.
But yeah the fuel was ment to have oil in it, likely you've damaged your motor already.
Maybe do some more reading.

serrath · Mar 4, 2014

Theon said:
Mate, you got a lot to learn about 2 strokes.
But yeah the fuel was ment to have oil in it, likely you've damaged your motor already.
Maybe do some more reading.

I'm on here now to do some reading but I appreciate the suggestion. Wasn't aware of the oil thing; I hope I haven't damaged my engine. Would this be the reason why my engine may not be working? If I swapped in the correct mixture, is it possible it would work then?

It had about 1/3 of a tank of the premix in when I filled it and I drove it maybe about 2km total... is it almost certainly damaged or is it possible that I had enough residual oil to make it work?

I'll try swapping out the oil tomorrow anyway, hopefully that'll work... What a rookie mistake

serrath · Mar 4, 2014

Also if you have some suggestions about where to start reading regarding this sort of engine; most of what I've found assumes some prior knowledge already

oylavabeer · Mar 4, 2014

where u at mate im near perth

serrath · Mar 4, 2014

oylavabeer said:
where u at mate im near perth

Pity, I moved from Perth literally a month ago now. I'm living on the Gold Coast now, could have really used some help to teach me a few things about how to maintain the engine so I wouldn't make mistakes like this

Live and learn, I guess

Theon · Mar 4, 2014

As fantastic as the internet can be, Your local library may be a good place to start.
Otherwise try and find a mate with a dirt bike, chances are he'll know a bit.
Very good chance you have damaged your motor, but without having a good look at it, I don't know how much damage.
But my experience with people running not enough oil in there wippersniper would lead me to at least taking the head off and having a look at the bore.
Again with a book infront of you, there's no need to be hunting through cyber space with grease covered fingers, But better still, find a mate with a Dirt Bike.
Chances are he'll have the right tools and a bit of knowledge.
These motors are better suited those with a little mechanical ability, otherwise can be a heart breaker.

bluegoatwoods · Mar 4, 2014

Okay, our new pal 'serrath' did operate his bike without knowing as much as he'd have liked. But he didn't know. We gotta be able to do more than just tell him this.

I'm not sure that printed material will be able to help you all that much. No doubt it'll have info about engines in general. But what you need is info about these particular engines. And you'll get more info like that searching this forum.

For your fuel you want to mix in oil that is actually meant for this use. You'll be able to find it at hardware stores, places that sell lawnmowers, etc. Just ask them for 2 stroke oil. They'll know what to give you. For breaking in an engine a mixture of 40 parts gasoline to 1 part oil is the most common mix. If I'm converting to metric properly, then you'll want 5 milliliters of oil mixed in 2 liters of petrol.

I've got one of these engines mounted on a stripped down frame in my basement. I'll come back and post a photo or two to show you where you can find that spark plug and the rest of the electrical system.

bluegoatwoods · Mar 4, 2014

Okay, here's a photo of where to find the spark plug.

The spark plug is what actually ignites the fuel mixture that is in the cylinder, pushing the piston down and generating the force that makes your motor propel your bike down the street. The energy for this spark is generated by a device called the 'magneto' that is mounted right next to the engine's crank-case. Here's a photo of it's location.

This bike/engine are not fully assembled yet. So there's something missing. The magneto is connected by wires to a black box called the CDI. They're usually mounted on the bike frame. That's probably where yours is. The CDI is connected to the spark plug by thick single wire.

The magneto generates a low voltage electrical current. The CDI takes this current, holds onto it for a moment, bumps it up to higher voltage and then lets it go to the spark plug at just the right moment.

You're going to want to start by figuring out if this system is working properly. When you're out buying that two stroke oil you might as well ask the store people for a cheap Ohm-meter. They can be had for about $10. (in the USA. Probably not greatly different in Aus) You're likely to want it. If not now, then sometime in the future.

Remove the spark plug from the head of the engine. You'll need to pull off the wire that runs from the CDI to the spark plug. Then un-thread the spark plug from the engine. Pop the wire from the CDI back onto the top of the spark plug.

Now prop up the bike so that the rear wheel can spin freely. Lay the spark plug down on the top of the engine so that the threads are making contact with the engine. Spin the rear wheel or push on the pedal. The piston should move up and down pretty easily. You should be able to hear air being pushed and pulled in and out of the spark plug hole.

And you should also be able to see a spark at the tip of the spark plug.

If the answer to that is yes, it still doesn't mean that there's nothing at all wrong electrically. But this'll be a good start.

Come back here with your results and we'll help you diagnose things from there.

maniac57 · Mar 4, 2014

I tend to agree with Theon, finding someone to help you in person will greatly speed your learning process. Teaching you the basics via computer will be much more difficult.
I'm sorry to say a certain level of knowledge is assumed on almost any forum, and a true beginner is likely to frustrate anyone trying to help. I feel your pain, but do not have the patience to try teaching you basic concepts online.
Find someone local to you with a dirtbike or with engine knowledge.
Maybe a local motorcycle repair shop with two stroke experience would be willing to help?
Even if they won't work on it for you, they should be able to help you learn what questions you need to ask.
Sad to say, from to sound of things, you ran straight gas and possibly damaged it. Running without oil in the fuel will lead to cylinder bore damage, galling, busted rings and possibly seizure. If it still turns over, it may not have enough compression to run due to damage from lack of oil.
Type terms into the search box at the top of the forum page. This will give you links to threads about whatever you type in and should help you learn about your engine.
Carb, sparkplug, oil mix, cylinder repair, cylinder inspection, etc. are some terms to start with.
As you learn more, keep posting and we will help as much as we can.

Theon · Mar 4, 2014

Thank you Maniac,
My patience is short at times,
But I have leant a lot from books!
Agreed though these motors are 'Different'.
Sad to say, but if it was running and now its not and you didn't touch anything else, it likely needs a rebuild, but I'd check for spark first.
But if I had done that to a motor, I'd be taking the head off and having a look, it's only 4 nuts, but get a hand to put it back together if your not confident.

serrath · Mar 4, 2014

Thanks so much for the suggestions. I'm at work over the day today but on my way home I'll pick up some oil, a gas can and put the proper mix of fuel. Thanks especially for the help on locating the spark plug and magneto too, that's exactly the type of advice I need

If I siphon out all the gas and replace it with the correct mixture, is it okay to test it then or should I check the spark plug at the same step? It sounds like these are two separate systems so there's nothing wrong with putting in the oil and testing it first, no?

Since it has run without oil, do I need to do anything extra to oil it or is it enough to just put in the correct mixture now?

bluegoatwoods · Mar 4, 2014

You should be able to test-start after merely putting in the new fuel mixture.

You won't even need to siphon. Simply pull the fuel line off the carburetor, put a fuel can under the loose end of the line and then open the fuel valve and drain.

By the way, the others are probably right in guessing that this engine has been damaged by running without oil.

But the good news is that a new engine is not really all that expensive at all.

serrath · Mar 5, 2014

bluegoatwoods said:
Okay, here's a photo of where to find the spark plug.
View attachment 68398

....
Remove the spark plug from the head of the engine. You'll need to pull off the wire that runs from the CDI to the spark plug. Then un-thread the spark plug from the engine. Pop the wire from the CDI back onto the top of the spark plug. ...
Come back here with your results and we'll help you diagnose things from there.

First of all, thank you so much for such an informative response. this was very helpful and I got onto it as soon as I got home. I spent the day googling 2 stroke engines and the consequences of not having the correct mixture and I've learned a lot about that.

When I got home today, I first drained the fuel, mixed 2L with 50mL of 2 stroke oil (40:1 ratio, as was suggested earlier in this thread) and tried it out - still had the same problem. I'm not sure about the choke, though; should it be "up" or "down"? The labels on the choke are in japanese so I don't know if up is "open" or "closed"; I tried starting the bike when the choke was up, down, and in the middle and none of those options worked.

So I will try to check the sparkplug next. I removed the wire connecting the magneto to the sparkplug however I ran into a bit of a problem and I wanted to get some advice before proceeding.

I've taken a picture of the sparkplug which I've attached below. The sparkplug is this white thing, right? How do I get it out, do I need to turn the sparkplug independent of this gold bolt below it or is it attached to the gold bolt and I need to turn the gold bolt to remove it?

I tried turning the gold bolt and it is really stuck; if I'm going to remove it, I need to purchase a sparkplug wrench or something; I have a ratchet set but the bits won't fit over the sparkplug to get at the bolt. Is there a standard size for these sorts of motors for a spark plug for purchasing a spark plug wrench or will I need to measure it for my bike?

Before I do this, can you confirm if I'm on the right track here? Should the bolt be this tight? I tried removing it with pliers and I couldn't budge it but I also didn't want to force it

And thanks again for your help. I know you have better things to do than take pictures of your own bike to help me out and the effort isn't lost on me.

If the engine has been irreparably damaged, is it possible to purchase just the engine independent of the chain, sprocket, sparkplug, gas tank etc and just bolt the new engine where the old one sits? I looked on ebay and could only find "complete" kits but it seems that, if I damaged my engine, it's just the engine that's broken and I can't think of a reason why a new one wouldn't be able to work with the existing infrastructure on the bike frame.

Theon · Mar 5, 2014

If you think that your really going to enjoy this bike, my advice is get a whole new kit, then you will have all the spare parts you need,
That's if you can't get it to run.
You may learn a lot from a new kit, and then you can pul your old motor apart, and learn to fix it.
Just a suggestion, I have 5 motors now lol.

bluegoatwoods · Mar 5, 2014

Theon is right about that. An engine only can be bought, but a new kit is not a whole lot more expensive. And then you have spare parts. That's how I've done it. After building a bike I order a new kit. It goes in the attic waiting until needed.

Anyway...yes...that 'gold nut' is what you want to turn, counter-clockwise, to get that spark plug out.

I'm a bit worried about the fact that you couldn't get it out with just pliers. Though that should be done only very carefully when needed. Still, it should have done the trick.

It could be that that engine got so hot that those threads are 'welded' in place.

Still, it's worth trying to get that out of there. When you do try turning your pedals and see if the piston goes up and down easily. If the answer is no, then that'll be a good indication that there's been damage in there.

sboricic123 · Mar 6, 2014

This link explain a bit how a 2 stroke works and may have some information for you in the future. It may not be the same brand name of engine you have, but most work the same.
http://www.grubeeinc.com/USA/Magneto Mystery.html

Motor not engaging, new to this, PLEASE HELP

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