20 Most Recent 2003 Yamaha YZ 250 - Page 8 Questions & Answers

1.8 gallons

Once full of fuel and gear oil it is virtually 100 Kilo (just under)

Did you bleed the air out of the rear master cylinder and brake line? Be sure the master cylinder has brake fluid and don't let it get too low while bleeding the brake. Bleed the master cylinder first, then the wheel caliper.

Ask yourself this questions?

1: How log has this been siiting?
2: Did I emptyout the carb bowl before i stored the bike?
3: When was the last time I had the carb cleanned?

Basically, you have a carb problem. It needs to be cleanned, and the jets in it are dirty. Always remember to empty lout the carb when not in use. Or use Stabil, a fuel stabalizer, it keeps your fuel from turning to a funky gel.

The other problem you have about full-throttle is probbaly a partially clogged primary Jet, a dirty fuel filter, or a simple fuel starvation problem. All of the following are simple remedies to eliminate as your problem.

1: Make sure that there are no kinks in the fuel line. That there is no obstructions in it.
2: Can't stress it enough, A clean fuel filter.
3: Make sure that your fuel tank has propper breathing, for fuel delivery to the carb.
4: A clean air filter, and that it get enough air for your bikes need.
5: Removal and inspection of the Carb.
6:Upon removal, make sure to take note of the neddle setting. You mentioned plug foulling, the neddle might be set too high, or something is impeeding it from propperly sitting to bootom (dirt). Or a kink in the throttle cable
7: choke! chec it it. It might not be returning back.
6: Also take into account elevation and tempertures. Ridding down in baja, at sea level in the heat. Is not the same as Moab, Utah, in the Fall.

If it presist? then its time to get deeper into the Carb.
let me know what happens?
Jerry gt

You dont. The flywheel is keyed to the crank, and the pickup, or stator that picks up the spark signal is bolt on, not adjustable.

Check a couple of things before going back to increasing jet size. First, it may sound a little strange but make sure the vent hose and gas cap are functioning properly. Yamaha has a check valve that allows air to come in but prevents gas from coming out if you tip it over. Just blow thru the end of the hose and make sure it's open. I've had this problem with my kids YZ, couldn't figure out why the jetting was all over the map and found the vent wasn't working. Bought a new gas cap and hose and problem solved. Also, check the e-clip setting on the jet needle. If someone set it towards the top, it could be lean no matter what jet size you run. Should be 1 position either side of the middle.
Also, quality of fuel and oil makes a huge difference. The book will tell you to run a minimum of 94 octane and a 24:1 mix of Y2R oil. While the oil mix is a little rich(32:1 is sufficient, and Y2R Yamaha oil is reaaly good) the octane is critical to 2-strokes. It's hard to find anything over 91 octane at the pump, and non-oxygenated fuel is critical(no ethanol!). Find a source for good race gas 102-110 octane, cut it half and half with pump 91 non oxy. and mix it 32:1 with Y2R. Once you jet for this combination, don't vary from it and you'll have no problem keeping it running strong!

Any thing over 200 psi is good - remember to hold throttle full open when kicking over to get an accuratre asesment and can take 10 - 20 kicks to get maximum reading on the guage

It can only be carbi more than like pilot jet and or air jet the simple answer is clean all jets but I personally would buy and replace all jets and throw the old ones in the bin if the bike has sat for years they would be rubbish by now
if your not confident with carbi just un install it and take to local bike shop they will service it pretty cheap would only take them 30 minutes ish?

These stators YZ 2003 you can replace for about $150 (ebay) truth is unless you have the meter to test i you cant test only guess from the symptom such as most common is engine dies once warm
then to take somewhere to be tested they no doubt will charge when ever I suspect it I just replace it and eliminate the possible problem especially on a older bike 05 or older.

The engine number will not give you what you need. The VIN is the key. You will find the VIN number stamped into the center steering stem that the forks attach to. Call a Yamaha dealer with the VIN and they can tell you what year and model of bike you have.

A “very helpful” rating for this answer? Thanks!

you just fill them right up, ride it for about 5 or 10 minutes not flat out just enough to heat the motor a little then check it again if its not full top it right up it'll find its own level

G'day. The torque specs for the 8mm head bolts is 18ft/lbs.the jug?(cylinder or barrell) is just tightened down even & firm, as there is no acess for a torque wrench.
OK. other things to note.
Clean the cylinder first in solvent(kero or fuel).Then in warm soapy water in a bucket. Dry-(compressed air is best for this-wear eye protection).once dry lubricate all power valves with oil.
Using a clean white rag-soak the end in your 2 stroke oil & wipe the inside of the cylinder surface untill the rag comes back clean(you will need to do it a couple of times-turn the rag over & do it again).Lube the new piston just before assembly-Also pour a little oil down the main bearing oil holes & over the big end too.
Other things to be sure of are-
Piston on the right way round-arrow to the exhaust.
Rings right way up. Some 2stroke dirtbike rings will only go one way up.Look CLOSELY at the ring ends-on the upper or lower surface there may be an etched dot or "T" or "N" or other marking. the mark goes facing up(on both rings unless single ring piston).
rings positioned with end gaps over the locating pins(the ring grooves have a pin in them to stop the ring turning)
Piston pin clips in correctly.
Powervalve moves freely.
Again-watch when you fit the cylinder-it can be tricky to keep the ring end gaps over the locating pins as you feed the cylinder over the piston.
Hope this all helps
Regards(done this a thousand times)Andrew Porrelli

2003 mate . . .last 2 diggits on chassis number

Sounds like you have a bent shift lever. It is expensive to fix but critical befor other problems occure

The frame number is the Vehicle Identification Number. If the engine is the original engine, then the engine is a 2004. If it is not the original engine, the engine numbers will not identify what year the engine is. The only identifier is the frame number. Engine numbers are useless.

Whether it is a four stroke or a two stroke, If you take the right crankcase cover off you should be able to access and replace the shift shaft. The mechanism is on the opposite side of the motor from the shift lever. You may have to remove the primary gear that contains the clutch pack to get the actual shift shaft assembly to slide out. The good news is you should not have to remove the engine from the frame or split the cases to do the job.

set the chain? you mean the timing? did you take the cams off. let me know what ya wanna do

Chances are that some trash has gotten into the float bowl and is intermittently plugging up the main jet. When the bike dies the suction on the jet dies, the trash is no longer blocking the jet and the bike starts right up.

check for any compression leak if no then change the piston rings.

Try tapping the carb with the wooden or plastic handle of a small hammer, or screwdriver, otherwise, you need to remove the bottom bowl, and then the float pin, to get the float out. (The needle is usually where the dirt gets, between the needle and seat.)