New (kind of) WR250F any hints.

[webbrace]

Well i found one and had to by it.2001 WR250F. It only has 100 miles on it. So any info on how to make this thing go a little faster?
I am looking into the throttle stop screw. I heard you shorten this to 20mm. And to cut the grey wire. I am not sure were that is? any help on that one would be great. I am looking into pipes/spark arrestors?
The bike will be used for desert racing in CA. Has anyone geared them up? Will they pull taller gearing?
Thanks for the info.

 

[Boozer]

webbrace, go to www.thumpertalk.com and conduct a search on all the questions you have asked. be prepared to spend a few hours looking through all the archives though!
i too have a WR250F, and have done all the free mods to it, and then some. They include: YZ cam timing and air-cut valve mod.
BK mod and HB mod to carby
usual air box lid and aftermarket filter
YZ needle and jetting
R4 pipe and so on.

if you are a bit disappointed with the kick your bike has now, don't worry because there is alot more where that came from. I have gone one tooth higher on the front sproket, and it pulls 130km/h, which is more than enogh for me (most of the time).

 

[webbrace]

Thanks for the info. Did you go for the same year YZ jetting? Also what is the BK mod? I am out in the garage trying to find the grey wire now.. and thanks for the hint. I will head on over to the Thumper talk site and check it out.

Has anyone put on a YZ front # plate? what year did you use?
Thanks again.:)

 

[Boozer]

i have put a 2001 YZ number plate on my WR. Fits right on. Even put a YZ fender on the back, and again it went right on.
Look at the wiring loom next to the CDI ignition box on the right hand side of the bike. The grey wire can be found there, where the socket for the loom is. You must disconnect it by cutting a small section out and then insulating the ends (similar to a vasectomy). Best free mod for you guys.
There is so much information about the BK mod that i would be foolhardy to explain it all in detail here, but generally: the acc. pump on the FC carb usually has a squirt duration that is far too long. This causes the bike to bog slightly when the throttle is hammered open. Most bikes come with a squirt that is about 2 seconds long. The founder of the BK mod suggestes a squirt duration of about 0.5 seconds for best pick up. You need to test the acc. pump before you do anything. To test, remove the carby boot from the intake section of the carby (air box). Remove the boot and wedge it behind the frame so you have a visual down the throat of the carby. Members on TT suggest to remove the air box and subframe, but this is a total waste of time in my opinion.
Once you have a visual on the acc. jet (the brass thing sticking out of the throat), crack open the throttle and see how long the fuel shoots for (You may need to use a flashlight to see inside). If it is a couple of seconds, then you need to do the BK mod which is easy. If it is way too short, like 0.1 seconds, then your'e in trouble and need to do the HB mod, which i needed to do. This is more complex to do, but made a big difference to my bike.
Basically, the BK mod is an adjustable stopper that limits the amount of travel on the acc. pump push rod lever (look at page 4-14 in your manual, and it can be seen on the bottom diagram, where the finger is pointing to).
The HB mod is a way of increasing the travel of the push rod, and it involves removing the factory stopper on the bottom of the acc. pump diaphram, and to shorten the lever that operates the acc. pump linkage arm (4-14 again, this time the middle diagram). If this is shortened, then it will increase the travel of the push rod lever.
i went to the equivilant YZ needle, a 40 pilot and a 172 main. Jetting will be different for everyone, but if it is jetted correctly, then starting will be very easy. This may be a good starting point for you, maby.
If you look at the left hand side of your bike, down near the gear lever, you will see two plugs. One for finding TDC and another to turn the crank. You must check these to see if they are lose. One member over at TT lost one plug, and a fair bit of engine oil. Obviously this can be engine threatening if it happens at the wrong time, so applying some loctite to these plugs would be a good idea. You may need to lean the bike over to its right hand side, so oil doesn't seep from the holes.
Another good idea is to re-grease your steering and swing arm bearings, as these came from the factory deprived of grease, for some reason.
Does you chain make alot of noise, even though it is adjusted to specs? your chain block (the front one that wraps around the swing arm) is lose and that is making the noise. Remove it and apply a strong sealant like Sikaflex to the block, and then re-install. If you don't, sand and dirt will be trapped under there, and the movement of the chain will cause it to cut a grove into the swing arm. Good one to do while re-greasing the swing arm linkages.
The oil drain plugs are easy to strip during oil changes, so its a good idea to use a torque wrench to tighten these, if your'e a bit heavy handed. 20nm for the sump drain bolt and 23nm for the frame drain bolt. That's all you need. Many people have gone too far, and it's just a big hassle to fix later.

 

[webbrace]

Boozer, You are the man:D Thanks for all the info. I will let you know how everything works. I think i may drop the rear sprocket down 2 teeth, to try and get a little more top end out of it. Again thanks for the tips.

 

[BUCKWHEAT]

The two plastic timing plugs can be secured by placing tape over them. I use a very strong shiny tape that is also used for sealing home a/c condenser units. The tape lasts about five rides before it gets tattered too much and needs replacing(this only takes fifteen seconds). It makes it very easy to glance at the screws to make sure they aren't working themselves out.

Thump on!