20 Most Recent 2001 Yamaha YZ 426 F - Page 4 Questions & Answers

get a leak down test it answers all questions gasket leaks or valve leaks piston leak down its the only way to tell answers with out tearing it down again you can do your self or your local shop can do it
My guess would be leaky intake valve giving blow by under compression and I have seen plenty come back from machinest still leaking when you assemble them back together
Leak down test is the answer then you will know where to start

Well bad news is yes to replace shaft you do need to split motor
But I have seen a few solutions that are a bit back yard mechanic jobs but they work !
you could tap and thread a small bolt into the the gear lever 90 degree's to the shaft then it has something to tighten down on the shaft
I have even seen guys put a spot or two of weld on the end so you can reach it to grind off if you need the lever off again at any stage
Some gasket glues can work also if you still get could tight grasp from just tightening the lever on the shaft then some good old gasket glue can be enough to increase diameter of the shaft to get even better grasp from the lock nut and when it sets also helps with securing the lever to the shaft and unlike glue it never sets rock hard so you can always get it off again if you need to

did you just get it?....do you have a manual for the bike....on the waterpump their is a coolant drain bolt....their should be 3 bolts, it is the bottom bolt, put a big drain pan under it remove the bottom bolt, then take off the radiator cap.and it should all come out.out.. i would use a 10w40 semi synthetic. also get a manual for that bike, you can get one on CD-ROM on ebay for about 4 bucks or if you google it you can download a pdf manual right on line for about 6 bucks...ya need to know how much oil your bike takes. i think it takes 1.2 liters, but i would make sure. hope this helps

I am speaking from my Yamaha XS1100, with 4 carburetors.It is a 1980 model, but the carburetors are always gunking up, especially if it sits over winter with gasoline in the tank. This also happens more frequently with the alcohol laced fuel that you have to buy now days. The alcohol causes it to absorb water that mixes with the gasoline and alcohol to form a sticky gunk that blocks up the orifices in the carburetors. The first thing that you can try is to get some Seafoam additive, or maybe Textron. Pour out all of the gasoline in your tank and change the inline filters if possible. Fill the tank with fresh gasoline and add the Seafoam in a generous amount. Allow the bike to sit over night and try to start it. You may get lucky and get the bike to fire up. If it runs rough and doesn't smooth out, you may have to clean your carburetor. See: http://www.bikebandit.com/houseofmotorcycles/2002-yamaha-yz426fp/o/m8901#sch252680

For a breakdown of your carb.

In the UK climate, I would use a 5W 40W semi synthetic. That will cover you if there was synthetic oil or Rock oil in the engine and allow you to upgrade to fully synthetic in the future, if you want to.

No. The engine oil and transmission are the same. Use recommended engine oil. (5w-30, Yamaha sells good semi-synthetic and synthetic)

Too much fuel. Adjust float level in carb.

There is no problem, that's how it works when the engine is not hot.

http://www.articlesbase.com/motorcycles-articles/how-to-adjust-dirt-bike-suspension-3944349.html This is way easier than the way I would have described it so I hope this helps you happy fixing

Bring it back .. work should be under warranty of some sort. Also if the engine is running but stalling due to fouled plug then maybe the oil injector is not adjusted properly or the oil/fuel mix is not right for some reason.

Get the thing running and warmed up. Turn the mixture screw in until it starts to stumble and wants to stall. Then start to turn the screw out until it starts to run good and pick up engine speed let it run for 30 secounds then turn the mixture screw in a 1/4 turn this the same on all carberators they baiscly work the same

Hehehe, you have cracked cylinder wall. Replace the engine or have it professionally sleeved. Best is just top replace it.

Hi, Its a 98 yz400f, body style is moto-cross. and was manufactured in japan.happy riding......yz-maniac.

WR F are 4 stroke.YZ are the 2 stroke models.If it is a wr,and you let them idle for more than about 1 minute,they all blow out coolant.They need to be moving to keep things cool.Hope this helps

OK do this. go to any auto parts store and get a bottle of a fuel tank additive called seafoam. follow the directions on the bottle regarding how much to add. After you add this and drive 5 miles your problem should be solved. Joe

I use 1800 cc which is almost 2 quarts

Massive oil consumption is not normal , unless you just have a leaking seal. Even the four stroke race bikes require a regular rebuild. Either is is over due or it was not done correctly. A new piston, ring set, gasket set with valve stem seals, and either a hone or bore should fix it right up.

you need a new top end

rectifyer or diode type

Your model should be yz426f thats what i went under mine as all the time and found parts. They might not have parts for that bike it is kind of hard finding parts for that bike i had a problem finding parts for mine.