20 Most Recent 2004 Yamaha YZ 450 F - Page 6 Questions & Answers

u have put the impeller seals in the wrong way round .they must face each other .sidecover seal faces out waterpump seal faces in

how do u do you do timing on yz450f i put a new crank in pro with lining up marks

You will need to clean the carb, and maybe buy a new float needle jet,
It is also critical to check valve clearances regularly

Sounds Like Spark Knock. Go To 93 Octane Gas And Select The Right Gear For Conditions. Do Not Lug The Engine. Lugging Will Damage This Engine Quicker Than Over Revving Will.

If it gets hot quick, could have a problem with the cooling system, blocked radiator,leaks?
Pressure test radiator and cooling system.
They will backfire if they get too hot.
If its just been rebuilt, check head bolts, valve clearances

all u got to do is clean the carb and if u find anything broken or worn, replace it. inside the carb theres a little cylinder were the small needle shape piece of metal connected to the floats,it goes up and down in the little cylinder and can possibly have some dirt, sand, grit lodged in there. if u have a manual thats fine, if not, u can be like me and use common sense cause u have to carefully unconnect all the wires connecting to the carb, then get a smaller size screw driver and unscrew the 4 screws connecting the float bowl to the carb, then turn the carb upside down and slowly watch 4 a little white piece of plastic, roughtly a 1 square piece, all it does is help prevent the gas in the bowl from slosthing around, i mean i lost it a million times and it did affect ****. only the best **** talkers and littles boys that think there the **** or RC4 will need that piece. but back to it, just carefully remove the float then unscrew the floats and clean them. if u got a air compresser thats great cause u can blow the air out of the tight spots, u can grab one for 40-50 bucks. then unscrew the cap were the throttle cable enters the carb, pull it out and clean it. make sure to clean out the entire float bowl. real quick u got to unscrew the accelerater pump cover and clean it out,oh and the little brass insert on the left side part of your carb if your looking at it from the back. thats your hot start. follow the hot start cable from the handle to the carb, then unscrew it if it is not already seized, u need to take it out and put a very small amount of grease on it. and remember if u get stuck just think of the situation and use mad common sense and youl be alrite. and since your asking a question that is easly fixed i no u aint a pro so just dont take anything off that i didnt tell u to and youl be just fine

You might want to check the rubber intake & exhaust manifolds for cracks. with the engine running, spray some carb cleaner around both rubber manifolds (Sparingly, short blasts, don\'t soak out of it) and listen for a change in the engines RPMs. if it goes up, or down, that could be your problem bro.......

there is a coller on either side of the wheel, they will really only fit in their correct side, as they locate in the seals before the wheel goes in the swing arm, there is a thin washer with the nut, checy the adjusting blocks are the right way, with the adjusting bolt heads touching the edge with the step

How much oil does the air filter have in it? If it's over oiled, it will drip into the box and fill up the drain plug. The foam filter that comes with our atv requires oil to trap dirt. Some people unknowingly will apply too much oil and it will drip, especially when it's hot out. Take the filter off, clean it with Dawn Dishwashing liquid. be sure he filter is dry, then re oil. I like Uni oil in he aerosol can. Spray it evenly but not too much, then rub it in with your hands, have a rag ready.

you might be running it to lean adjust the carburetor or raise the needles to let more fuel throughyou might be using the wrong type of fuel

I have this same problem did you find the solutinon?

FYI to tombones49, you suggested a 32/1 gas oil mix, this bike, however, is a 4 stroke, thus rrequiring no such mixture. Maybe some sleep woulde wise...

sounds like maybe a coil issue

It must not have any spark, check it and repair as nessasary

Headgasket leak?If you have not done so already try filling up the rad(when cold) and run the engine with the rad cap off and look for air bubbles, or you could go to a radiator service centre to check for carbon monoxide in the rad.

Please get back to me if you require further asssistance.

When you have difficulties starting do you get fuel to the cylinder and sparks on the plugs when you pull out the hi tension wire from the engine?

Hi,Did you tried replacing the CDi for your bike?Tell me what happen when you replace or borrow a CDi from your friend, just to check if it is the real culprit......

Sounds like you need to service the carbs as it sounds like your bike is starved of fuel with the choke off and some of your jets may be blocked.

Slightly warm the engine remove oil filler cap remove sump drain bolt and allow to drain
remove oil filter cover and remove oil filter wipe out excess oil with clean rag
install new filter and bolt on cover install sump drain plug
refill with 1100ml oil of your choice - Your Done!
Additionally you can remove the oil strainer basket from the frame but no one does this too often if at all
regards Jamie

With setting the cams it can only be right or wrong there is not really any way to be a little out unless the cam chain itself is severely over stretched...
set (I) mark on fly wheel to be visible within the marks on the inspection hole of ignition cover (always a good idea to cross reference TDC by probing the piston through spark plug hole as I have seen many flywheels shear their woodruff keys and give incorrect TDC readings) any how, once at TDC set the cams ( lobes facing outwards with the dots on each cam aligning best you can with the head. with your finger take out the slack of the cam chain through the tensioner hole and double check all dots and (I) mark on fly wheel still all line up correctly - if so then your good to button all back up... Don't be alarmed if takes a few goes it's perfectly normal to have at least couple of attempts to get all correct.
You want your valve clearances to be 0.20 on the exhaust and 0.10 on the intake side a tiny amount bigger gap is kind of OK but never smaller or you will do damage !
Backfire although can be caused by timing out or valves clearance incorrect in my experience is nearly always due to lean on fuel, could be worth double checking your pilot jet and circuit is all clear - compressed air cleaning them is best or stick new pilot jet in to be fool proof ! and air clean the hole the pilot jet screws into..
Happy to elaborate on any points if needs be, just let me know
good luck regards Jamie