250 The 1999 YZ250

Trfsrfr

Trfsrfr

Put 2 hours into her at the track today. She's jetted wrong for our winter temps, and was "boogery" as I like to call it (rich) at WFO, but I dealt with it and re-learned how to ride a 2T. I think a smaller MJ will build some power and boost top speed, which she needs. If y'all remember not long ago I was complaining about needing another gear...well I added a 52 tooth rear sprocket, and she still needs another gear! I think this "competition" model bike was made for supercross.
All-in-all, a great day at the track, bike was very strong.
Bottomed the forks a bunch though, and have the clickers almost all the way up...but then If I'd just man up and hit those jumps full on, I bet the bottoming issue would go away. Of course, I cant hit those jumps full-on until I get the bike leaned out...
A great day nonetheless :-)
 
Trfsrfr

Trfsrfr

I forget when I last ran this bike before I got it replated, but I looked at the settings from ProCircuit that you gave me @Mihylo33, and my MJ is a 172s, but it ran good til about mid-throttle then started getting that boogery sound as I like to call it. But my plug (an Iridium br9exi) is black and sooty.
I was thinking it was rich cuz of that boogery sound, but now I'm 2nd guessing myself with that 172 MJ.
I'm guessing my float is off.
Took the slide out but cant get the needle out cuz I dont have a socket that fits. Not sure why cuz I'm pretty sure I've had it out before.
What size is that thing?
 
Last edited:
Mihylo33

Mihylo33

Trfsrfr:
I forget when I last ran this bike before I got it replated, but I looked at the settings from ProCircuit that you gave me @Mihylo33, and my MJ is a 172s, but it ran good til about mid-throttle then started getting that boogery sound as I like to call it. But my plug (an Iridium br9exi) is black and sooty.
I was thinking it was rich cuz of that boogery sound, but now I'm 2nd guessing myself with that 172 MJ.
I'm guessing my float is off.
Took the slide out but cant get the needle out cuz I dont have a socket that fits. Not sure why cuz I'm pretty sure I've had it out before.
What size is that thing?
Click to expand...

6mm I think.
You know the drill. Set the floats, check the jetting.
Post pics of that plug.
 
Trfsrfr

Trfsrfr

Dont need to post pics I dont think. Its black and sooty, just like you all have seen. You all know what it looks like.
Tearing the carb off now.
After I burnt down the kiddos CR80 I learned lots, especially in how it sounds when its way too lean (a $350.00 lesson). Since then I bought a float measuring tool, and its been a good purchase. (the kids 80 and 125 have been screaming since). No more eye-balling it. And if you read my post in the other thread you know my close-up vision is gone.
I'm sure I'll have it dialed soon enough.
When are you in AZ @myhylo33?
 
Mihylo33

Mihylo33

Trfsrfr:
Dont need to post pics I dont think. Its black and sooty, just like you all have seen. You all know what it looks like.
Tearing the carb off now.
After I burnt down the kiddos CR80 I learned lots, especially in how it sounds when its way too lean (a $350.00 lesson). Since then I bought a float measuring tool, and its been a good purchase. (the kids 80 and 125 have been screaming since). No more eye-balling it. And if you read my post in the other thread you know my close-up vision is gone.
I'm sure I'll have it dialed soon enough.
When are you in AZ @myhylo33?
Click to expand...

Just because it’s black and sooty doesn’t mean it isn’t lean or rich. Oils like Yamalube PJ1 and golden spectro can and will leave a plug looking sooty. Other oils make the plug appear wet and rich. It’s just how it burns. It could be black and sooty from lugging the motor. This happens a lot as well because a good portion of people don’t run the bike in the meat of the power band.


PALMER84ONE:
Probably around the same time I/we will be full time...
Click to expand...

I’m not ready yet. It all depends on when Lisa’s boss retires.
 
Trfsrfr

Trfsrfr

I remember this thing now. This POS carb, the PWM that nobody seems to like. I've never had this thing running correctly.
The float is at 7.5mm, needle position #2, 172MJ, #7 slide.
She gets all flubbery around mid to WOT. The plug isn't a good indicator cuz I remember I let it idle till the gas ran out.
 
Last edited:
Trfsrfr

Trfsrfr

Redordead89:
Post the pic!
Click to expand...
Okay okay already! I'm waiting for it to warm up out in the garage. I dont operate well under 75 degrees.

Edit - here you go, keep in mind this was after I shut the fuel valve and let it idle till the float bowl was empty;
Dec 2018 Plug.jpg
 
Last edited:
Trfsrfr

Trfsrfr

The only difference I have in the current setting is the float is set 1mm lower (at 7.5) than it should be. Everything else is bone stock settings. If I put the float at 6.5mm, thats gonna richen it, yes????

1999 YZ250 Carb Specs.png
 
Mihylo33

Mihylo33

Trfsrfr:
The only difference I have in the current setting is the float is set 1mm lower (at 7.5) than it should be. Everything else is bone stock settings. If I put the float at 6.5mm, thats gonna richen it, yes????

View attachment 32240
Click to expand...

No. After 5.5 mm it will richen. 6.5 is the mid point.
You could just end it all and get a JD jet kit. However I still found myself jetting through out the race day with my JD kit, but not too much. Mostly just air screw settings and pilots to crispen up the throttle response.
 
Trfsrfr

Trfsrfr

Good to know.
However, as much as I hear this carb (pwm) is a piece of shit, its not possible that Yamaha would continue to sell the YZ250 with a carb that didn't work. So therefore I believe I can make it work. I've read in many forums about guys switching to the PWK and that solved all their problems...I tend to think that they didn't know what they we're doing to start with, therefore I dont need to buy a different carb, but just learn how to tune mine. Tell me I'm wrong.

So here's what I did tonight - I raised the float to 6.5. Then I dropped the MJ to 168, like the ProCircuit rec's that @Mihylo33 linked to. I left the 50 PJ in it, as it seemed to idle and rev up to mid throttle just fine.

As of now it sounds pretty good on the back of my truck. We'll see what happens at the track this weekend.
It sure would be nice to hear this thing rip like she's supposed to. Even last weekend at the track she was way faster than she ever has been. I cant imagine what she'll be like when I get her dialed completely.
 
Top