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Wr250f 03 Mods

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Posted by: barrie36---------------------

Hi all,my friends just bought a 03 wr250f,its got a fmf power bomb header and a fmf titanium silencer ,what other mods can be done to this bike.I read one of the other threads about the wr450f mods someone did,can these be done to the 250


Posted by: Rich Rohrich---------------------

What part of the powerband are you looking to change?


Posted by: ukdean---------------------

top end mainly,running 13t front and 52t rear, only had the bike a few weeks. been reading about the blue/grey wire mod but not sure if it applies to u.k bikes.Any help would be appreciated


Posted by: Humai---------------------

Quote:
Originally Posted by ukdean
top end mainly,running 13t front and 52t rear, only had the bike a few weeks. been reading about the blue/grey wire mod but not sure if it applies to u.k bikes.Any help would be appreciated


My experience with these bikes relates to the 01 model. Our bikes (AUS/NZ) did not use the grey wire (it was open circuit)and were therefore already "fixed" as delivered. I assume the UK/EURO bikes are more like ours than the USA's. Our bikes are delivered with a one piece shiny stainless muffler that has a non-removable baffle. As far as I can see, the US ones still have a black muffler with removable baffle.

The 03s and beyond use an auto decompressor which prevents the other popular mod for the 01s and 02s being done - retarding the exhaust cam one tooth. The solution for the 03s is to fit the 03 YZ250F exhaust cam, which is relatively inexpensive.

The YZ timing mod gives the bike a much stronger mid range which can in some cases allow the bike to be ridden a gear higher in comparison - it's definitely worth doing. Top end horsepower is not greatly enhanced but mid range is dramatically improved. On my bike, this mod required going two steps richer on the main jet.

Check your valve clearances while you're in there and remember to retorque the cam bearing caps carefully as per the workshop manual.

If you ever pull the head off, check the ports for a mismatch between the port casting and the valve seat insert - mine was a little mis-aligned and benefitted from a careful blending. Do not touch anything to do with the head and ports unless you are familiar with this type of work - it's a fantastic piece of work as it comes from the factory.

Also, the bike should be much easier to dial the jetting if you completely remove the airbox lid. Mine was a nightmare to jet until I did this mod.

They are a great off-road package. Good luck and let us know how it goes.


Posted by: ukdean---------------------

thanks for the advice.i stripped all the tank of last weekend to check on the grey wire and it had a male/female connector already on it so i've now re wired it to a switch,took it for a quick blast and it did feel a bit more responsive in the mid range.were waiting for dry weather this side of the pond so can't say for sure, and i don't know what difference it makes to u.s bikes but what i have read you notice straight away.My bike has also got the full stainless exhaust with built in baffle, again when i bought the bike it come with a fmf power bomb and titanium back box. The exhaust cam seems like the way to go so i am thinking of getting the motor rebuilt in the near future so i will find out how much the exhaust cam is going to cost but i suspect over in the u.k it will be a lot more than the u.s!!,thanks for the advice and i will let you Know soon as , Dean :thumb:



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