2001 Yamaha YZ 426 F - Answered Questions & Fixed issues

minha yz426f quando vou de terceira marcha devagar mas quando eu acelero a fundo ela engasga , mas ? so de terceira marcha de rewsto nao faz isso

On this model you measure oil height with the fork compressed and spring removed. Pour 5 weightfork oil in until itis 90 mm from the top. lift and lower the damper rod inside the tube a couple times and recheck your oil level.

2 1/2 quarts

Drain and replace the gas with fresh.
Remove the air cleaner and spray carb cleaner into the inlet. Work your throttle a little then put everything back together and try to start it.

2 to 3 clicks. Make sure you fire the bike up a couple of times to make sure is running good.

Time for a valve adjustment. You have done the right thing by replacing the spark plug and cleaning the carb. Check your valve cleareance and make sure is up to specs.

Some 426's have a decompression lever and some don't if there is been a cam job done.

Hi there,Have you checked your accelerator pump daiphram ? Could be old and needs replacing or dirty.

hold the decompression lever in and kick it slow then let go of the decompression lever and give it a good kick without using the decompression lever.

clean plug .. although new plug if old fuel or unbalanced carb it may quickly foul. if this works you may need help to work out whats causing plug to foul.

It is not normal, The oil is coming from the engine lubrication system and it sounds as if you have not renewed the rocker cover gasket when the engine was rebuilt. Check the torque settings on the head bolts and that no oil is getting into the coolant.

http://www.freepdfmanual.com/2008/08/08/2002-yamaha-wr426f-and-wr400f-p-service-manual

if its the one by the choke it is the "Hot start", if you have trouble starting in warm weather it should help the bike start....i am no mechanic but that is my understanding.

If it starts but won,t idle I would adjust low speed jet on carborator.

Right hand side right next to the water pump in between the big clutch cover and the water pump cover you will see a small cap about 6- 8cm has 3 bolts they will be 8ml bolts or maybe allen bolts on the older YZ
Tip drain all your sump oil first before opening and lean bike over to the left as much as you can to save big mess of oil coming out when you open this cover. Don't forget to smear some clean oil on the rubber on the end of new filter before installing it will help seal it and keeps in place a bit so you can install cap back on easier...

I would think head gasket due to the piston pushing compression out to your coolnat system.
Do a compression test

Things to check 1st. If it overheats after riding for a while, check the air filter. If the filter is not sealed properly, air will get in between the seal and the airbox causing the bike to overheat. Other possibilities on a bike that old would be clogged radiator tubes(replace), bad water pump(replace impeller)
Please comment

Either you got air in you cooling system or, you have wrong combination of air and gas in your motor. Good luck :P

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