Yamaha 2 stroke died and won't start

[Neodrivesageo]

Hi. I'm new to the dirtbike community. I recently found myself with a 125 CC 2 stroke Yamaha dirtbike. It's the first one I've ever had. I was riding it in an open field today, and it kept acting like it wanted to die. It started stalling out, but I popped the clutch and it started up again. This happened a few times, and finally it stalled and wouldn't crank. I checked the spark plug and the side electrode was broken off (I'm guessing it came out through the exaust.) I replaced the spark plug immediately, expecting it to start right up since it was still warm and I tried kicking it for a good 30 minutes to no avail.

Any idea what the problem could be?
Thanks
Louis

 

[_JOE_]

You need fuel, air, compression, spark and timing. If the ground starp broke of the plug there's a good chance you did some internal engine damage causing low compression and the no start condition. Is the spark plug wet after you kick it for a while?

 

[sharky243]

For the cost of gaskets, I would atleast take the top end apart to have a look inside. As Joe said, spark ?, compression (120 psi minimum) ? Fuel ? A broken reed can cause a no start aswell.

 

[Neodrivesageo]

Yes, the spark plug was wet. I am no mechanic, but a friend looked at the spark plug and told me he thought there may have been water on it. I took his advice with a grain of salt though, because he is a pill junky.

I do get spark, there is gas in it, and there appears to be compression. (I put my finger over the spark plug hole, and it did make my finger burp.) I don't now how to find out if it's getting air, or if the timing is correct.

 

[_JOE_]

It should have strong resistance at the lever when you try to kick it over. If it is very easy to kick chances are good you have low compression.

 

[mathd]

I am sure you will have to do a top end.
Dont kick it more, if there is internal damage this will make it worst.

I would check the reed first then take it apart if it was mine.(that is if there is spark/fuel)

The exact same problem happened to mine this summer, it did melt the piston/rings with the spark plug ground strap ;)

 

[Neodrivesageo]

Thanks for the help everyone. I'm pretty good with my hands, but I've never worked on a dirtbike before. Is there a thread on this site that will show me how to do a top end? I also did a search for reed but I couldn't find anything relevant to my problem.

The bike does have good compression, BTW.

 

[julien_d]

Google is your friend...

http://www.lmgtfy.com/?q=yz125+top+end+rebuild

A service manual is always a great help with such an undertaking as well. You can get one from your dealer, or many places on the internet in downloadable format.

 

[mathd]

Thanks for the help everyone. I'm pretty good with my hands, but I've never worked on a dirtbike before. Is there a thread on this site that will show me how to do a top end? I also did a search for reed but I couldn't find anything relevant to my problem.

The bike does have good compression, BTW.

Try and get the manual if you can, you will not regret it.

 

[rmc_olderthandirt]

Having the ground tang break off the sparkplug is really bad! It is possible that it blew out the exhaust without causing any damage but it is also possible that it wedged in between the piston and cylinder and has been digging a trench.

Did you ever look at the spark plug before then? What I find hard to believe is that a newbie in a field could ride the bike hard enough to result in the spark plug damage. That is something that I would associate with riding at high speeds, full throttle.

What grade of gasoline were you running? That bike probably needs premium pump gas and if it has been modified it might even need an even higher octane race gas. Running too low of an octane would result in detonation which could lead to spark plug damage.

What oil mix are you running?

If you never looked at the plug before then I would guess that it had been that way for a while and not related to your current problem. What is common with a newbie on a two stroke putting around in a field is to foul plugs. Two strokes need to be run hard enough to get the cylinder temperature high enough to burn the oil off the spark plug. A lot of slow riding can foul the plug and cause these problems.

Usually changing the plug for a new one (not another old fouled one) will get you going again.

If the spark plug looked wet then it is probably wet with gasoline and an indication that it is flooded. Another explanation to the stalling is that the carburetor is allowing raw gas to dump into the engine. If you end up with raw gas down in the bottom end the engine will cause it to be so rich that it simply won't run until that gas is gone. Try this: shut the gas off at the tank to make sure that no more gas can flow to the carburetor. Start with a clean dry plug and kick it over a bunch. Pull the plug and see if it is wet. Keep going until it either starts or the plug comes out dry.

If the plug was actually wet with water then you have a blown head gasket.

Two stroke top end rebuilds are easy. If you do the rebuild before the cylinder is damaged they are fairly inexpensive.


Rod

 

[Neodrivesageo]

Thanks rod. I was definitely not riding like a newbie. I know I probably should of went easy on it, but I was having too much fun. I was definitely riding it at full throttle. I didn't look at the spark plug before that day. It was actually my first day out riding it in the dirt (I putt putted it on the street to see how it ran, but nothing hard)

The oil mix is 32:1, and I'm pretty sure the guy I got it from would of put standard unleaded octane 87 in it. I put a brand new spark plug in it after it died on me, and it wouldn't start. I'm thinking it may just be flooded, because I've since had it sitting in a spare bedroom (I have no garage, and live in the ghetto) and the entire room smells like gas.

Thanks to everyone else as well. I downloaded a manual.

To the guy that told me to use google, how do you think I got here? ;)

 

[jayhedrick]

Dude buy a gasket set and rip into the top end.. That's really the only way your going 2 find out how much damaged you have cause by trying 2 run the bike with the metal in it.. Gasket set is cheap but your more than likely going 2 have 2 do a top end rebuild...

 

[Unregisteredd]

I need help I can't get my bike to start by kicking it and when I push start it

You need fuel, air, compression, spark and timing. If the ground starp broke of the plug there's a good chance you did some internal engine damage causing low compression and the no start condition. Is the spark plug wet after you kick it for a while?

 

[rmc_olderthandirt]

Unregistered Guest:

Instead of replying to a four year old thread start a new one!

Provide us with more information:

Year, make & model of your bike
What you have done to try and fix it
How long has this been happening
When did the bike run properly?
etc.

Rod