hey guys. i got a 2004 yz125 from a friend. its beens sitting for two years and wont start. i put fresh gas in, cleaned the carburetor, put a new spark plug in and it wont start. its got spark, and fuel. its my first yz and i dont know how the compression should be. the kickstart is real easy to kick. when i try and pop start it it just boggs down. what could the problem be? thanks!:thumbup

fuel, air, fire and squish.

check to see if it's actually getting fuel, ie. does it smell like gas when you kick it many times?

if you're breathing it has air.

it's got spark, you've tried that.

squish is the only thing remaining and it sounds dubious at best. They're not a gentle kick.

Been sitting for a couple years, check the exhaust to see if something has made a nest in it. Seen that multiple times on bikes that have set up over time.

oh good call. Bird/mice nests can bitch the air part.

fuel, air, fire and squish.

check to see if it's actually getting fuel, ie. does it smell like gas when you kick it many times?

if you're breathing it has air.

it's got spark, you've tried that.

squish is the only thing remaining and it sounds dubious at best. They're not a gentle kick.

whats squish?

I believe he's referring to compression. ;)

A 125 should kick over relatively easy. But, definitely not without resistance.

O right lol. No, it has compression and its good but i still dont understand why it wont start! Maybe advance the timing?

O right lol. No, it has compression and its good but i still dont understand why it wont start! Maybe advance the timing?

No I would not mess with the timing.
I would take the carb apart , replace parts as needed ( float, float valve-etc). Most people can't clean a carb properly with one try- lots of orifices and things a seasoned motercycle mechanic knows from doing it a thousand times.
Or it's compression issue or some other thing related to sitting.
What was the reason the bike was parked?
In what state,winterized with fuel unit?
What exactly have you done to it?

Agreed. I'd pull the carb apart again and clean it thoroughly.

Also, any chance a reed valve might be bad?

It was my friends dad. He was hitting fifth year with it, till his foot slipped and down shifted with no clutch, flew over the bars, cracked his head open, and broke his back. He justs wants me to fix it. Ever since then its just been sitting.

Agreed. I'd pull the carb apart again and clean it thoroughly.

Also, any chance a reed valve might be bad?

Lol whats a reed valve?:D

Lol whats a reed valve?:D

Reed Valve explained (http://en.wikipedia.org/wiki/Reed_valve)

still nothing! checked the reeds and there good. i took off the header, and a shit load of oil poured out of the pipe. and sometimes it backfires when im kicking, only once in a while. also when i try and pop start it, it just boggs down. any other help?

what ratio are you mixing the pre-mix at.

and

the reason I asked the questions about how the bike was stored:
if the fuel petcock was left on(when the bike was parked) the fuel can sometimes leak down into the crank over time the gasoline evaporates leaving two stroke oil
if the fuel was allowed to leak down you could have a crankcase full of old fuel as well as a transmission literally not allowing the atomization of the fuel or allowing the fuel to make its journey from the carb to the crank to the piston. yes the fuel goes thru the crank before it makes its to the combustion chamber.
the sludge that was once two stroke fuel may now be working its way out of your bike and ending in the expansion chamber.
change the trany fluid, change the spark plug , and then try again. eventually the fuel will wash out the gunk that has accumulated in the crank case. that is if my theory is correct.

Im mixing at 32:1 i believe. I think the petcock was left on. that could make sense! what tranny fluid do you recommend?

yamalube motor oil is sufficient , there are oils packaged under the pretense that 80/90 wt is better , but the truth is the two sets of numbers 20-40 yamalube oil and 80/90 two stroke trans oil are very similar .
doubtful gas made it all the way to the transmission but you should change the oil any way.
it will probably keep puking out the crud for a while . if you have spark and fuel eventually you will get it started. the oil in the pipe will not do any thing good for your muffler .
the trans oil is a specific amount usually a number is stamped on the crankcase near the fill hole followed by cm3 ... cm3 is another way of saying cc's

on the off chance this does not get any better you may have other problems like a sucked seal whereas you are bleeding trans oil into the crank case . highly unlikely but an example of possibilities

Ok i drained the oil. I took the exhaust back off, and kicked it a few times. Instead of it oil sputtering out of the head, its gas. Is this good or bad? It will putter like for a 1/4 of a second, but just a putter.

as long as you are running pre-mix and havent changed the jetting I dont see how you could be doing any damage. as far as why I is not running I don't know. are you sure you have spark?

100% positive about the spark. Should i try a new plug.

Come on someone has to know! Anyone?

Bump!

Are you sure you have the carb settings correctly? Meaning the choke is right, the slide is set correctly, etc? When it's trying to start and it sputters, is your hand completely off the throttle? Or, is it cracked open a little?

I think if it ran when they parked it you a screwing up pulling carb apart unless you a very familiar with it's operation and maintance. Are we sure when this bike "crashed" the throttle was not hung open during the crash leading to a piston problem. Also is the power valve functioning correctly. If it were me first thing I would do is pull the plug out put bike in gear push it around some and clear all the crap out of the cylnder. Put in a fresh plug kick it twice no throttle no choke the put on choke kick it no throttle and if nothing is seriously wrong should start. two strokes are also very suceptible to anything stopping up the pipe. In this area what we call mud dobbers a type of wasp will build nest in an opening like a muffler so make sure no stopped up exhaust.

i got your solution i had a 2002 suzuki 2 stroke quad that had been sitting for ages like yours and all you really have to do is rebuild the carb and put lucas oil fuel stabilizer in your gas tank fires right up!

u said this guy dropped gears at like 40 mph?? When u rock the bike back and forth when it's in gear can u feel the gears grabbing? Cuz If he that caused him to flip then it probbly fucked ur clutch up too. Try doin that In all gears... What year did you say the bike was?

Its been over a year he probably sold it

you got spark but is it good spark? i have a 2001 yamaha yz 125 i took the carb off cleaned it new plug kicked my ass off nothing and i was getting a yellow spark bought a new coil put it on got a nice blue spark bike started 2nd kick.

its blown up, top end is shot the wrist pin is hopefully blown out the exhaust, probably detonation damage done to the cylinder