Top 20 2003 Yamaha YZ 250 Questions & Answers

Here is a site with good info about modifying your bike. Thread My wr400 street conversion

Its not supposed to work on your bike "BUT" I have a 2006 raptor 660 CDI on my 02 warrior 350 and it works better than stock and is supposedly "non-compatible" with the warrior the only thing different with your bike and the 03 is the TPS

just turn the gas off

Check the reeds pull the carb and take the 4 bolts from the intake and look at the reed cage and make sure they are closed

check your shifting drum.may have left a pin out of the shifting drum.

Without knowing all the variables here. How old is the clutch that is in the bike now? It may just be worn out, and need new fiber plates and discs put in it. Are all of the clutch springs the correct ones, or if they are old, might be time to replace them. When its slipping, what kind of riding are you doing ? in mud, sand, or on hard ground ? What size engine and bike do you have ? Is your clutch cable and adjuster the stock and correct pieces for your bike ? or aftermarket ? Have you had the clutch apart recently, and do you know for sure that you put it back together correctly ? ( See Service Manual ). Lots of variables to consider... without knowing, you might consider these things I have mentioned. Thanks.. Hopefully these will get you going again.

http://www.pdfmotomanual.com/index.php?r=site/page&view=manuales&order=t&key=Y&make=1752&lang=ENG Loads of downloadable manuals on the above link....all free. You might find what you are looking for amongst them.

Oil rings are worn inside the motor.pretty much engine on it's way out.

strip gear box and check all selector forks and cogs for wear etc ! check gear lever shaft etc ! P...

If its yz It is a 2 stroke and has on valves per say. It has a reed valve located between carb and head. Lots of times they need to be replaced or re-clearance (Make sure they are free of debri and flat on the housing.

As in all gears? Or just 1 spcific gear range? Might need to pull the transmission apart and have the gears "backcut" or just replace them entirely...

do you mean it sticks down after kicking ? if so the return spring or cog on the kicker are damaged ! remove side cover and you can see the problem ! P...

hi there this could be a bad spark plug or the carbie jet blocked or if you have a fuel filter it could be blocked ,if the motor is smoking then may need new rings,at the worst you could have a broken ring which is not letting the piston move properly , hope this helps

Check and fix there in order: check spark plug gap and colour - replace if it has any cracks in the insulator;check air cleaner and clean thoroughly if at all dirty;remove and clean carby float bowl - if there is any sediment, replace or fit fuel filter, if there is "paint-looking" coating on anything, clean entire carby.

I have always had great support from yamaha in regard to engine building assistance. If you goto yamahausa and use the contact us field with a request for the benchtop procedure for assembling your yz250, they are willing to send it to you at not cost if you are persistent

Repair manual

Hi mate this will be the oil & water seals the leak from weep hole is basically a warning light to tell you it needs replacing asap, you need to remove impellor, carefull not to lose the spacer washer behind it...then remove the water seal clean the surface it came from and replace with new seal. Now to do this 100% I would always replace the impeller shaft as the shaft wearing is usually what caused the seal to fail and I would also replace the oil seal which is the other side of case that you just changed the water seal (oil seal sits behind the small bearing) I would also consider replacing this bearing but maybe not critical? all up the impellor shaft the 2 seals and bearing last time I bought cost about $160... no special tools required just quite a bit of time required as you should really remove the outer engine case to access the impellor to undo it and to get to the oil seal and bearing, how ever I know guys do just open the water pump cover then rattle gun off the impellor only replace the water seal then install the impellor and cover back on then ride away! this will work and will fix the leak but is definitely the incorrect way to repair this and will be temporary fix but thought you may like to know this alternative as is very handy way to do it if your on a race meeting and just need to get through the last race or two. hope this help cheers... Moto X Parts online.com

Check the points for proper gap and clean. The old school bikes used more than just coil and plugs. Also, often overlooked, check the kill switch connection. Often this is the case on Yamahas.

Nevermind those other answers, if its running on all 4the cylinders but just real sluggish and missing top speed then listen up, let's first rule out the possibility of a damaged impeller, now locate your airfilter box and remove the filter, just throw it away because last I checked dirt really doesn't settle on top of water, now locate your throttle body and remove the intake tube from it, now take out the 4 bolts that hold it on and find your flame arrestor element. I've dealt with this problem many times only to find out that the geniuses at Yamaha had installed this screen right after the butterfly which accumulates airfilter material and clogs

Check the compression. It should have at least 100 psi,..if not,then its time to rebuild the top end..IE piston,rings,bore cylinder. If compression checks out,i would start with the power valve. Two stroke dirtbikes power valves are notorius for gumming up and sticking,causing them to not rev correctly.