WR jetting after YZ timing

[JWW]

I have been dealing with this for a couple weeks now. My bike is a Canadian Model 2001 WR250F with FMF Q and airbox lid removed. I have also unhooked the gray wire but it didnt go to anything anyways. Stock jetting was 170 main, 42 pilot, OBEHP needle and 60 leak jet. I am located in Southern California.

I first installed a FMF Q pipe and the bike ran great. One week later I pulled the valve cover and rotated my exhaust cam one tooth clockwise for YZ timing. Keep in mind the only change was to the cam.

I have changed my pilot jet from leaner (38) to richer (50). I did bump the main up to 175 and 180. I have also moved the needle clip up and down but never changed the needle.

After all these changes I can not get rid of my bog. On flat ground the bike is great. When I hit any incline it just starts bogging. It gets so bad that I need down shift until I can get the rpms up.

From midrange to top the bike is fine. I have totally cleaned the carb. There are no obstructions in any jets. No matter how I jet I end up with the same results. I also checked the timing and it is correct.

Could this be caused by the needle size?

Any thoughts?

 

[JasonJ]

Yup, guys usally switch to the YZ needel at the same time they change the timing. Check thumpertalk.com as I dont know the needel or PNs off hand, there are sevral jetting options available and some like Taffy jetting will give you plenty of power and save fuel, your PJ and main jet is on the pigish side, so are mine, Im at a 40 PJ I think and a 180 Main but Im on WR timing now and I get good milage and I have a 3.3 gallon tank so who cares anyway :) . A 50 PJ sounds kinda fat though.

 

[Humai]

My WR, an NZ spec one probably quite similar to the CAN one in that the grey wire mod is already done, is running YZ timing and a YZ250F OEM muffler. I also removed the airbox lid, which was upsetting the carburation no end.

I went down one size on the pilot and dropped the stock needle two clip positions to get rid of the richness at lower throttle settings. I went from 170 stock main when in WR timing mode to between 175 and 180 depending on conditions with YZ timing.

The bike runs spot on now and is very strong in the lower mid range.

I agree with JasonJ in that your pilot seems too big.

 

[scarem]

Your settings sound way off.
Try this..
Purchase a OBELN needle from your local dealer. (YZ250F Option needle)

OBELN-3rd clip
40 pilot
75 pilot air (Stock)
160 main
162 main air
fuel screw- 1.5 to 2 turns out

Or

OBELN-3
42 Pilot (Stock)
75 Pilot Air (Stock)
165 or 168 Main
200 Main Air (Stock)

 

[Jonny426]

Just for the fun of it, take your valve cover off and re-inspect the cam timing. Sometimes the intake cam slips a tooth while you set up the ex. cam. Everything looks cool until you release the tensioner and recheck TDC/cam timing marks. I have used the OBELN in my 426 and a friend's WR450-great midpower. I run stock pilot jet ,pilot air jet,main air jets,but up10to15 on the main jet. When i tried larger pilot jets my bike needed the hot start every time warm, and idled very rich no matter where the screw was set.

 

[JWW]

Update - I rechecked the timing and everything ok. I did rejet it leaner and things are getting better. I think I need to drop one more on the pilot.