YZ 250, need help!

Hi, I just took apart my 2003 yz250 because it was not starting, cleaned out the carb, and air filter is fine, but it seems to not be getting fuel, we used an air compressor and put it where the gas hose connects to the carb, and it sprays gas out into the carb as if it was stuck in there, so we put it back on but when we open the throttle there is little, then absolutley no gas coming out, and also cleaned out the float bowl, could it be the power valve is shot?

Edited by ll5MAV9ll

Hi there

in IMO no as the bike should start with the powervalve closed. Maybe the exhaust is full.



start with spark, then check compression while you are there, timing and fuel are all that are left. timing is not going anywhere if you did not mess with it.....my money is spark or fuel.

forgot to say that yes, i am getting spark, but no fuel is being pushed through the carb, and when i kick it you can hear the engine turn over like its going to start, but it dosent fire up, and this thing has tons of compression, im almost out of breath after about 10-15 kicks

spark, gas, compression......which one is missing?

Just a hunch but My guess is compression........without high enough compression there is not enough vacuum to suck the gas from the carb. Compression is read in PSI with a compression gauge.

use the compressed air to blow out the jets they might be clogged up than take the air filter off and try to start it with out it

"cleaned out the Carb" - If the bike has been sitting for any lenght of time cleaning the carb properly will require complete dissassembly, spay/soak with carb cleaner and compressed air thru all of the passages. You may want to replace the main and pilot jets, some times is realy tough to get them completely cleaned out. . . . . Also did you drain and replace the fuel?

How do you know that no fuel is flowing through the carb? If you take the drain plug out and turn the fuel on will fuel flow out of it? Is your plug fouled? Is your air cleaner clean, is your exhaust free of obstructions?

As metalman says a thorough carb cleaning might be in order with carb cleaner. Make sure the float is functioning properly, all jets are free of clogs by spraying carb cleaner through them. etc

When I got my bike it had been sitting outside for a period of time and a dirt dobber had built a nest in the fuel inlet, and nothing was getting through. I had to put about 150 psi of compressed air against it to blow it out.

Might sound stupid but have you actually checked the hose that goes from the carb to the tank, or how about to tank itself? I was thinking that maybe the bike was starving for fuel...

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