"Bogging" 250 WR

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#1
:o

Sorry for my bad English but I really need your help.
From the first day I noticed some bogging, mainly on pavment ,mainly at steady speed,...ok Ok do not say that WR is not for pavment.
I believed that it was just question of chain.
Now I am cetainthat my bike bogs.Just like some dirt is in the carb... I cleaned the carb ...no result. I do not think that this si an ignition problem...your advices are wellcom

RakO
 

LawManNv

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#2
My WR250F does the same thing if I run it on the pavement at a steady speed although I don't notice it off road. It wasn't really bogging but more of a surging feeling. I think it has something to do with the carb. Since I bought the bike I have been having a hard time with the jetting to get rid of the mid range bog. After changing to YZ timing and then leaning out the jetting I think I finally have it. The bike rips now with no bogging in the middle.
 
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#3
Originally posted by LawManNv
My WR250F does the same thing if I run it on the pavement at a steady speed although I don't notice it off road. It wasn't really bogging but more of a surging feeling. I think it has something to do with the carb. Since I bought the bike I have been having a hard time with the jetting to get rid of the mid range bog. After changing to YZ timing and then leaning out the jetting I think I finally have it. The bike rips now with no bogging in the middle.
Would the jetting alone solve this problem ??
RakO
 

LawManNv

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#4
I wasn't able to completely cure the bogging with just jetting. Going richer on the pilot, needle, and main all seemed to help a little but the bog was still there. Changing the timing to YZ specs did much more to cure the problem. After the timing change I had to go back and lean the jetting. As it is now I am running the stock pilot #42, the needle in the third clip, and a 180 main. This is at 4000ft above sea level and 60 to 70 degrees. The bog is gone and the bike rips now. I don't think that the timimg change hurt bottom power at all and is well worth the time.
 
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#5
I have done badically the same thing as law with similar results. I also changed the leak jet from a #60 to a #90. As soon as it warmed up (75+ in SC) the bike ran horrible just off idle. I talked with Randy Hawkins' mechanic and he advised me of the leak jet issue. On that particular jet increasing the number leans the circuit. The WR comes stock with a 60 (US anyway) and the YZ has a 105. I have tried the 90 with good success, but have not yet tried the 105. I raced yesterday with an air temp of about 75 and probably 50% humididty or better and the bike ran very good.

For reference:
Main 178
Pilot 42 (stock)
Leak 90
Needle (stock)
Needle clip Pos 3

Altitude approx 300'
105 Octane race gas (same stuff Ivan is using, he may have more details on the fuel)
 
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#6
I have also done the same thing as LawmanNV and bentbarz. My midrange bog didn't raise it's ugly head until I changed to an aftermarket exhaust, then a change to YZ timing fixed it for the most part. The bog is basically gone for now but there is still a somewhat flat spot just before hitting the main jet. I may explore another exhaust when someone else releases a quiet system that won't rob my power. I'm hoping Dubach will be successful with his new one.

bentbarz- What did the 90 leak jet do for you? I have a 90 leak jet that I ordered when I got my Big Gun exhaust, but I haven't installed it because my bike pulls hard off the bottom. Also, when you installed the leaner leak jet, did you have to adjust your fuel screw?
Coop
 

Humai

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#7
Rako,

Yours is no doubt a Euro spec bike. Does it still have the stock one piece muffler fitted?

I found with mine (also Euro spec) that in stock trim, it ran horribly rich until well into the mid to top end revs at which point it would clean up into a good top end rush.

Removal of the airbox lid made the single biggest difference, making the bike actually "jettable" from that point. The Euro WR250F seems very sensitive to airbox capacity and flow dynamics.

Leaning the needle two clip positions (from number 4 to number 2 position from top) cleaned up the partial throttle mixture and now it's pretty close, with just a leaner pilot required from stock to perfect it.

Another thing to consider: the US versions of the WR250F seem to benefit from retarding the exhaust cam one tooth (so-called "YZ timing") as per the suggestions above. I have not seen evidence to suggest that the Euro and US versions use the same timing and would double check before attempting this. It may be possible that the Euros use the YZ timing already.

- Grant
 

RakO

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#8
- Grant [/B][/QUOTE]

Hi Grant !
Did you change the timing to YZ specs ?

RakO
 
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#9
BCooper,
As soon as the weather started to warm up, I got a real bad stumble just off idle, which was the motivation for the leak jet change. I tried leaning the fuel screw before changing the LJ, but the bike wouldn't even start so I could try it. That was about the same time as the Big Buck GNCC, so I made it a point to visit the Hawkins camp (had some time since I ruined a radiator 3/4 of a lap in). I did not have to adjust fuel screw, but it is a tad harder to start (two kicks) so I may back it out a 1/8 turn.
 
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#10
bentbarz, Thanks for the info. I'm not going to swap the leak jets until I have a problem. Hopefully, that problem won't arise.
Coop
 
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#11
WR Jetting

Just got a new WR250F (2005) to go with my '05 YZ 125. The WR seems to bog or run 'lean' wide open with the revs way up. Any suggestion on jetting? I have cut the the grey wire, cut the throttle stop, removed the muffler restrictor and opened the airbox by cutting out the two holes on the side. I haven't put a pipe on it yet. Would stock YZF jetting work? How are you guys gettin the YZF timing? Thanks for any help.
 
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#12
You will need to go to a smaller leak jet. Something in the # 40 range. Also check that the AC squirt is timed and not hiiting the plate
 

ZKDX

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#13
thumperfaq.com
this will answer all your bogging questions.

Get a zipty fuel screw, check your ap timing. are you running any exhaust mods, #40 leak jet, really should invest in a tach to set the fuel screw properly.
again read the faq thoroughly, i promised you won't be disappointed.
 
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#14
RakO said:
:o
Now I am cetainthat my bike bogs.Just like some dirt is in the carb... I cleaned the carb ...no result. I do not think that this si an ignition problem...your advices are wellcom
RakO
RakO.

Check your accelerator pump rod adjustment. Make sure that the carb slide opens a little bit BEFORE the accelerator pump squirts fuel. Many people adjust this the wrong way figuring the sooner fuel squirts in to the carb, the better the throttle response will be. In reality, the systems in the carb do not begin to work until the slide opens. Adjust the rod by bending the little tab on the cable bellcrank. Refer to your manual.

Also, when you cleaned the carb, did you remove the little cover at the bottom of the float bowl and clean in there too? This is the accelerator pump and water and dirt can get in there causing the pump not to squirt fuel.