Top 20 2004 Yamaha YZ 250 Questions & Answers

If you have a rad on that unit you have a warped head and the water is leaking into the piston.... stop using immediately as this problem will lead to major engine problem as water does not compress and will either crack the head or blow the Rings.. if no rad then check to see if there is water in the gas.... if neither then it is probably oil burning but that smoke should be blueish...

internal gear selector bent. your need a manual to fix.

The seal will have alip that faces to one side of the seal body. Inside it you will find a small spring around the lip or edge This has to face to the inside of the engine as the sump pressure pushes the lip harder onto the crankshaft and so seals off the gas mixture. As with all lip seals the lip faces the oil/water or in you case teh compressesd fuel mixture in the sump.

sounds like either the pistons have gone or could be seized engine mate it happened to my cr 250,

The hole is a weep hole, designed to drain coolant from water pump seal leakage or oil from bearing seal leakage from contaminating either system. So one of the seals is leaking, and you should rebuild the pump.
Looking at the parts diagram it appears the impeller is threaded onto the shaft on the YZ250....hope that helps, heres the parts diagram
http://www.mrcycles.com/fiche_section_detail.asp?section=50188&category=Motorcycles&make=YAMAHA&year=2004&fveh=1236

Once it leaks through the fork seals you will need to replace the fork seals.

The timing doesnt just go out of time on its own.
At TDC there wil be a dot on the ex cam sprocket that lines up with the front gasket surface and another dot on the inlet sprocket that lines up at the back.
Check valve clearances while the cover is off it is the most common problem.

mixture is to rich not all the oil is being burnt inside the head when you are driving the bike try turning the air screw in by half a turn then try it again you may have to play with the screw to get it in the right place for you bike

Hope this helps

John

theres 2 adjustment screws for your clutch

1 is by your clutch lever
2 is by the crank case on the right hand side of the motor

good luck.

the back firing is normal on a fourstroke and try cleaning your carb the carbs on those bike are a regular maintenance item if they set for any period of time they need to be cleaned

undo the big allen bolt on the bottom.(a rattle gun helps)
remove the dust seal
remove the circlip
use the fork leg as a kind of slide hammer to separate the top and bottom, and this will pull the seal out.make sure its clean and some WD helps the seal move
It may help to put the axle in and clamp the axle in the vice to hold the bottom end

Standard coolant (Green) Use the pre-mix and you won't need to add distilled water, otherwise use a 50/50 mix with distilled water only.

springs and oil. if you want any more info let me know. Dont want your money.

25.3 fluid ounces

On these two stroke motors they are pretty simple. You need 4 things to make them run. You need Spark.. Which you have. That covers the whole electrical part. You need fuel. Which is the most common thing that is making the bike not run. All it takes is a spec of dirt in the main jet to keep the bike from running. Or like you mentioned, the float is stuck in the full position. And not letting fuel in. Take the carb off and clean it with carb cleaner and blow out the jets with an air compressor. Also it needs compression. If you have a lot of hours on the engine, you might want to check the compression. If it is hard to kick over then the compression is probably ok. If it kicks over real easy then you might need to re-ring it. And the final thing that it needs is air. Make sure that the air filter is clean.

not sure what you mean by cover. if you want to remove the cap that plugs onto it, simply pull straight up. Try to pullaround the base firmly but gently enough nthat you do not detrot the cap., if your talking about the head (motor cover) then that is a whole other issue that you should really at minimal buy a factory service manual to do

replace water pump seal and shaft

hi ,
Is your carby well fixed? If your air intake is too big ,the bike will not run properly .
Make sure the carby is not taking additional air or not enough .
Clean the air filter , tune the carby with the mixing screw air/fuel

well first try the choke if it runs good when you pull the choke even a little then you need less air, if it runs worse then you need less air, in is less air and out is more air thats the air mixture screw.
idle screw is self explanitory start turning it if it idles up then your turning it up if it idles down then you are idling down usually in is up.

if it has an adjustable coil shock on the back u should be able to turn the collar on the botom of the spring to tighten it up, somtime's there is a spetial too needed