2004 Yamaha YZ 250 F - Page 9 - Answered Questions & Fixed issues

these bikes will loose water from the overflow if you sit and idle.Don't.Turn the motor off if you want to stop for more than 30 secs.They require air to go over the engine cooler to keep cool.Rule of the thumb is......turn the engine off if you are going to sit and have a chat or a look.This is important.Hope this helps

There is a sequence to follow when these bikes are hot to get them started.But first.Does the bike start easily when hot if it is push started? If the answer is yes,you need to use the hot start pull switch on the carby and the get the motor in compression before you pull in the small compression lever and slowly push on the kickstarter halfway down.Release lever and fully kick the motor over from the top of the kickstarter.Don't let these bikes sit around idling.They will overheat because they need air to get through the radiator.Hope this helps

milky oil is water mixed into the oil. Replacing the seals should fix the leak. Nothing special on the top end gasket.

The oil fill is on the top of the left crankcase cover. The dipstick is on the backside of the front frame down tube, just in front of the cylinder head.

there is no quantity that i can give you.....you have to fill that thing completely and make sure you have no air at all in it...maybe you can see this important step on you tube....otherwise the pressure of nitrogen is between 150-175 lbs depending on the way you like you're bike to absorb..make sur you place you're valving shim in right place if you change you seal....

you will have to remove the kickstart...drop oil...prestonne and then remove the big side case that finally will show you the back of you're impeler and then you can unlock it and take it off and change you're inner seal....

u shud hav a repair manual-lower end work is detailed n u need special tools n technique-the book explains this

simple just turn the idle screw in 1/4 of a turn mate and its done

hi buddy on the shock where the spring is on top you will see 2 nut big ones unscrew the top on and turn the spring or go on youtube and it tells you how to set up the shock for you using a tape measure

buddy sounds like your piston rings have wore or broken strip the barrel off and replace rings making sure you put oil on them when you install

You can buy pre-mix that is already to go in. Other wise 50/50 with distilled water. "Engine ice" also is a good alternative as a coolant that will actually help it run cooler.

ok, assuming you replaced the carb header and stator with aftermarket parts, then I would say you definitely have a jetting issue. that flat spot is coming from your engine starving for fuel. its taking the gas too long to get from the carb to the engine. you would fix this by adjusting the idle mixture on the carb. the first thing I would do is look for the fuel mixture screw on the carb. im not familiar with your specific model. but the screw is usually found facing down on the bottom of the carb, directly in front of the bowl. when you find it, turn it counter clockwise about 1/2 turn at a time until that flat spot fades away. if that doesnt work, then you will need to up the size of the pilot jet inside the carb. maybe 1 or 2 sizes would be enough. if you replaced the carb with a bigger carb, then you may not be able to fix this problem. in my experience, larger carbs will increase power, but usually throttle response, especially low end, suffers considerably. the reason for this is lower intake velocity and vacuum. basically, with a bigger carb it takes a second longer for the fuel to be drawn from the carb and properly atomize with the air. hope this helps.if I overlooked anything let me know! some more info on the engine/modifications and carb/jet sizes would help too. good luck.

That is a bit strange. Did the previous owner install stronger springs than the stock ones? Compare the effort to pull your clutch handle to what it takes on a new 125. Be sure you have clean 10w40 motor oil in the gearbox. No synthetics or special additives. Replace the rod and the lever assembly. The rod, lever and oil should eliminate the problem assuming the springs are stock.

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no buddy your mixture is too rich which means to much fuel is going in and not enough being burnt so the access fuel goes in the exhaust and then gets burnt in the exhaust which is a explosion so you get a back fire to cure this problem you need to screw the mixture screw in which is located on the carb a picture below will demonstrate turn this screw 1/4 of a turns in this will decrease the amount of fuel going in and stop backfiring good luck bud

From a YZ250F service manual >

Use 10w40 motor oil in the gear box. Don't use any synthetic oils, oil marked "EC", or oil with "special" additives. Stick with the major brands; Pennzoil, Quaker State, Mobil or Shell.

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check the carburator if there is a gas goes to it

HI.YOU KNOW I'M GOING TO TELL YOU A STORY ABOUT WHAT HAPPENED TO ME. THE SAME THING AND IT PISSES ME OFF EVERYTIME I THINK ABOUT.IT WAS A BAD OIL FILTER AND IT WAS NEW AND MY BIKE STARTED TO LOSS POWER AND THE KNOCKING THAN IT TIGHTENED UP. THERE WASN'T ENOUGH OIL GETTING TO THE TOP END. HA, I PRAY THATS NOT YOUR PROBLEM. JIMBO

Do a compression test.(Hold throttle wide open when doing this) Blow by normally is a sign of worn rings!

first try cleaning the jets sounds like pilot may have a blockage and its boggging down, as the bike been stood for a while ?
but also could be the crank seals

2 strokes should have a slight oil residue on them better running ruch than too lean

hi JT,

thank you for using fixya

below is a thread from thumpertalk on where to get the manual for yz250

http://store.payloadz.com/str-asp-id.106342-n.1992-2006_Yamaha_YZ250_Service_Manuals_Collection_247_74_MB_Other_Files_102-end-detail.html


YZ250 fork talk

http://www.thumpertalk.com/forum/archive/index.php/t-741170.html

hope this helps,

regards,

voodoo