Yz125 throttle issue

I'm buying back my 2004 yz125, I went and looked at the bike, kid said he ran out of gas and hasn't used it for a while so it's been sitting, I put gas in it and tried starting it but it wouldn't start, it was about 32 degrees outside, I sprayed starting fluid in it and it started but it seems the throttle is stuck wide open but I can still pull the throttle all the way back and it seems the throttle is free. The bike would then die and it seems like it is not getting gas and is only running on starting fluid.

Hope your not paying the same price you sold it for, 

depending HOW he ran it out of gas (under load) could have been bad for the engine.

Don't spray starting fluid in a 2-stroke!

Hope your not paying the same price you sold it for, 
depending HOW he ran it out of gas (under load) could have been bad for the engine.
Don't spray starting fluid in a 2-stroke!

No in not paying the same price, what do you mean by under load? Why can't I spray starting fluid in a 2 stroke??

Starting fluid will rev up the engine quite high but contains no premix oil. (you're running the engine with no oil)

It also hammers bearings hard because it ignites very easily, sort of like detonation/pre-ignition.

 

A 2-stroke engine relies on premixed fuel for lubrication and also internal cooling (fuel moreso than the oil for cooling).

While riding it somewhat hard, if the fuel runs out the metering progressively gets leaner

making the engine run even hotter. With no fuel and oil, it can lead to a seizure.

 

If you decide to get the bike back, pull off the exhaust pipe and have a peak at the piston thru the port.

Look for scratches and any erosion at the edge of the piston's crown (top).

Edited by mlatour

Hows the compression on the bike? 

Sounds like a good case of WAY cheaper than you sold it for. 

And all the above is spot on. 

Should fire up on the choke. I assume you tried that? That's the first step in solving the no-fuel or not-enough fuel during cold start.

Should fire up on the choke. I assume you tried that? That's the first step in solving the no-fuel or not-enough fuel during cold start.

Tried the choke

Okay, cold start is no throttle and choke. If the bike has the throttle part-opened, it's not going to create enough vacuum to start. Need to fix/close throttle issue and then it should start on the choke. Check that throttle cable is routed correctly. Sometime if you put it on the wrong side of the number plate, the cable is too tight and you'll get a high idle. When you release the throttle, you should be able to feel the slide hit the stop. If it's not, it needs more slack in  the cable.

 

For no-fuel flow, you'll want to check that the tank cap is loose (no vapor lock), gas flows from the fuel line with the tap on, that there is no grit or crud in the carb drain plug that might be obstructing the jets. It should start and run (maybe not the best) with the choke on, even if it's been sitting a while without fuel moving through the small/pilot jet. That's assuming you can get the slide to close.

If it dies when you gas it, even once it's run on the choke for a minute, you've got blocked jets and will need to strip the carb and clean/replace the blocked jets.

Whole deal sounds more like it should be approached as "how much will he pay you to haul it off".. :rolleyes:

Whole deal sounds more like it should be approached as "how much will he pay you to haul it off".. :rolleyes:

I sold the bike to him for $2,000, I was asking $1,600 for it but when I went to go look at it, it had those problems, how much do you think I should ask for?

With the bike in basically non-running condition, there could be any one, or multiple things wrong with it. The non-running part is probably a carb clean (it's running like it's wide open because of the starting fluid you sprayed in it), but once it is running, other problems may start appearing. What does the bike look like in general? Plastics all good, tires good, chain and sprockets? If all else is good, just doesn't start, the afore mentioned carb clean could have you running again. If the bike is trashed on the outside, it's most likely trashed on the inside too. Either way, it doesn't run, the guy obviously isn't interested in it, I'd offer maybe $300 if it still looks decent. if it's obviously beat on, I wouldn't screw with it as it could quite easily become a $$ looser nightmare.

You may be sentimental to it because it's your old bike (have memories of when it ran better)

but by the sounds of it you're no doubt now buying someone else's problems. Price accordingly.

Edited by mlatour
With the bike in basically non-running condition, there could be any one, or multiple things wrong with it. The non-running part is probably a carb clean (it's running like it's wide open because of the starting fluid you sprayed in it), but once it is running, other problems may start appearing. What does the bike look like in general? Plastics all good, tires good, chain and sprockets? If all else is good, just doesn't start, the afore mentioned carb clean could have you running again. If the bike is trashed on the outside, it's most likely trashed on the inside too. Either way, it doesn't run, the guy obviously isn't interested in it, I'd offer maybe $300 if it still looks decent. if it's obviously beat on, I wouldn't screw with it as it could quite easily become a $$ looser nightmare.

Everything looks good on the bike except that it has some mud on it, he could of at least cleaned it up a bit, when he bought the bike from me I had it in prefect condition with no dirt on it, I think it just bay be the carb issue, I'm going to look to the bike again on Sunday.
Hows the compression on the bike? 
Sounds like a good case of WAY cheaper than you sold it for. 
And all the above is spot on. 

Compression is good

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