20 Most Recent 2003 Yamaha YZ 250 - Page 9 Questions & Answers

did you put the jet in correctly ?? are you sure it aint upside down ?

ALWAYS have a fire extinguisher on hand when working on carburetors.
Remove the water trap bowl at the bottom of the petcock, (gas valve). Is there any water or trash in the bowl? Drain a cup of gas from the tank. Is there any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ). Fill the tank and use only premium gas.

Drain the carburetor. There should be a screw on the lower side or bottom of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new stock NGK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the idle screw and the air screw on the outside throat of the carb and spray into the screw holes as well.
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Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two adjusters down. Only screw these in until they LIGHTLY seat. Now turn each adjuster one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. This process should get you back on the road.

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

Heres Yamaha's site for old owners manauals and service manuals
http://www.yamahapubs.com

I would check sthe spark plug gap. Set it to 0.9mm
If too close it won't ignite properly also is the exhaust pipe standard? If not the timing and mixture will need adjusting.
Hope that helps.

I think you can clean it up without splitting the cases, but I'd pull it from the frame so that it can be turned upside down and flushed out.

To flush it, I'd want to use a fairly heavy flow of solvent (mineral spirits, for example) but not a lot of pressure- you don't want to wedge a fragment in the crankcase anywhere, you just want to flow them out.

Just turn it upside down and flush it, turn it, flush it, take your time. Give it a final rinse with acetone to remove whatever you flushed with and reassemble.

Don't be afraid to stick a mirror on a wire and get your little Maglight and examine every bit of the crankcase. It's sort of a shortcut job and doing it to the best of your ability will help ensure that all turns out well.

lp

The site link below has exploded view diagrams and parts list with part numbers, for all sections of the bike You will need to view the transmission, shift cam fork and shift shaft sections.
Cheers.


http://www.cmsnl.com/yamaha-yz250r-2003_model11246/partslist/

check your trans.Oil. It my be getting in your engine if so you crank seals are leaking or you are low on compression may need a top end.

To find the year on the vin provideing what make you have honda ,yamaha,ext,most owner manuals cover more than one basic bike ,example-honda 100 ,125 250,will all be in one manual .In the section of identafacation will tell you what you need to know? These books can be obtained online at any Honda dealer,yamaha dealer ,ext.

The tenth digit in the VIN will give you your year.

1980-A, 1981-B, 1982-C, 1983-D, 1984-E, 1985-F, 1986-G, 1987-H, 1988-J, 1989-K, 1990-L, 1991-M, 1992-N, 1993-P, 1994-R, 1995-S, 1996-T, 1997-V, 1998-W, 1999-X, 2000-Y, 2001-1, 2002-2, 2003-3, 2004-4, 2005-5, 2006-6, 2007-7, 2008-8, 2009-9, 2010-A and it starts over again along the same lines.

hope this helps

John

Not likely. would cause it to not run. you if this is a 2 stroke you may need to adjust your oil mixture. manual says 30;1 But 40:1 is much better.

Methinks the speedo head is lazy. Defective. Verify cable and drive have adequate lubricant. - Ned

Here is a chart. Please rate my answer. Thanks.

Sounds like the spark plugs are not properly gapped, carb flooding from too many tries and ignition timing chain has moved away from specified point. Just try to check those components.
Start taking the spark plugs out, gap them properly according to factory specification, use air compressor air duster to blow excess fumes out of the combustion chamber. Remove the engine/valve cover. Check whether the ignition timing notched are still properly aligned. if not then use the timing adjuster to tighten the slack else if already maxxed out then need to replace it.
Hope this helped. Cheers

I believe the 2003 YZs were the single chamber design, therefore this answer is based on that assumption. The fill procedure for dual chamber forks is much different, but I think they twin chambers came in 2005.

Use a good quality 5Wt suspension oil (or 7Wt if you want more dampening but this will make it a little more stiff through the small stuff). I recently began using Amsoil and I am quite impressed with it because it will not fade during a moto - not even in the rear shock. I am referring to Amsoil Suspension Therapy (or Shock Therapy - I can't recall the exact name, sorry).

With the springs removed, fill the forks to the top, cycle the damper rod up and down until it has consistant and firm resistance, top the fluid off to the top, lift the outer tube up about 6" then set it back down, top off, then let it sit until you see no more bubbles. Stroke the damper rod again to ensure there is no air and then draw out fluid with an irrigation syringe (see below) until your level is between 110 and 150MM in each tube. Make sure each tube is filled to the same level. One quart per fork is enough to do the job but you might need three quarts to have both filled prior to sucking the excess back out. I usually start with three bottles.

For a firmer feel, use more oil (110MM). For a softer feel, use less fluid (150MM). This is measured from the top of each tube to the level of the oil.

Just use a piece of clear tubing and an irrigation syringe - you can get one from a local animal vet. Just mark the tubing with a sharpie at the level you desire.

My standard setting was 135MM from the top using 7Wt oil. I am 160lbs and a mid pack A class rider using essentially stock valving with stock springs racing MX in Virginia, North Carolina and sometimes Maryland.

I hope this has helped.

Tri-Z 250 ?

Yz 250 :

http://www.bikebandit.com/houseofmotorcycles/1986-yamaha-motorcycle-yz250s/o/m8883#sch222048

YTZ 250 :

http://www.bikebandit.com/houseofmotorcycles/1986-yamaha-motorcycle-ytz250s/o/m8800

no filter required if one of these.

Clymer manuals are by far the best in my opinion. I prefer the old fashioned paper manuals over the PDF formatted manuals.
http://www.themotorbookstore.com/1563926628.html
Here is the site I use to buy manuals. This directs you to the manual you need, I've already selected the proper manual for you. If this is helpful, please vote accordingly. Thanks, Astrawoid.

Could be a number of things...
Black ooze is due to being too rich. You need smaller jetting. (Pilot and main) You can read the spark plug for jetting, as you want it to burn chocolate brown.
Also, a carbon plugged exhaust power valve can cause poor high rpm performance.
A compression test will tell the condition of your rings.

Hi,

You need about 500cc. of oil in each fork.

May be CDI, but check all your grounds first. Make sure you have a clean metal to metal connection of the coil to frame. Disconnect the leads going to the kill switch also. you may have a high resistance to ground short. Also, did you replace the lead coming out of the coil going into the spark plug? did you reuse the old lead?

Check your clutch pack. Cheers

Check the frame tube, left hand side below engine.