99 yz250 weird fouling plug problem???

[08 BANSHEE]

Originally Posted by dan151

yeah im having the same problem with my 99' yz250, kinda ironic haha, i ride for about two hours then the plug goes. ive gone threw 3 plugs. i drained the gas thinking mabe the fuel mix was to rich and mixed at 40:1 with yamalube 2r and it runs fine with the chock up then with the choke down it bogs and then dies then wont start cuz the plug fouls.

it ran perfect when it was 50 degrees but now its 80 and it fouls like crazy.

ive got a pro circuit pipe with fmf silencer and the guy before me said it was jetted fine. should i try going a little leaner on the main? or move the needle clip to lean it out a little more?

its jetted to rich lean it out

[dan151]

what do u reccomend i do? move the needle clip to a leaner position or try a smaller main jet?

[jcyamablue81]

For Minitrucker83 i totally agree with dajogejr! For you dan151 i wouldnt trust the last guy with the jetting. Check it for yourself cause that might very well be your problem with it bogging. Oh and you want to match your pipe and silencer. Especially with pro circuit and FMF. i know it wouldnt make a huge difference and 99% sure it wont fix your bogging problem but it is still good to match them up.

[dan151]

Originally Posted by jcyamablue81

For Minitrucker83 i totally agree with dajogejr! For you dan151 i wouldnt trust the last guy with the jetting. Check it for yourself cause that might very well be your problem with it bogging. Oh and you want to match your pipe and silencer. Especially with pro circuit and FMF. i know it wouldnt make a huge difference and 99% sure it wont fix your bogging problem but it is still good to match them up.

yep fmf gnarly is on the way! im pumped! and i ordered a wide range of jetting that just arrived today and im gunna play around with my set up, will let u guys know what works for me when the pipe gets here!

[jcyamablue81]

very nice! i wish that they made the gnarly for my 125! thats a nice pipe!

[dan151]

okay got the fmf gnarly pipe on my yz, checked the needle, at the 2nd clip position, put in a 172 main jet and left the stock pilot in, mixing at 40:1 and its about 65 degrees here in massachusetts at sea level. took her for a spin around the block and it ran like a bat out of hell! had no resistance what so ever and idled perfect. barely any smoke and no oil smug out of the exhaust.

and the gnarly pipe and the fmf shorty gave it a TON of low end power without robbing to much of my top and over rev! i was having trouble keeping the front down lol

hope this helped!

[dan151]

[fastman69]

nice looking bike, glad you got it runnin again

[minitrucker83]

First off sorry about the long posts! I like details. lol

Well I finally tore into my bike. I decided to tear into the carb to see what jets were in it. Luckily for me I found a major potential problem before it happened. When I bought this bike the air filter looked pretty new and clean so I never touched it and have only rode it a few times since buying it. Well I removed the carb and kind of took a peek at the reeds without removing the block. At first I was like something doesnt look right Ill check them out before I put the carb back on. I found the washer for my air filter stud, laying flat in the reed assembly. WTF!!! Checked the Boyseen reeds out and they looked pretty much new so I reassembled everything without the extra washer bouncing around. LOL I also repacked the FMF silencer as it looked as if it had never been touched.

Now as far as the carb it looked pretty clean and the float height spec'ed out towards the high side of the specs. Installed was a 172 main, 55 pilot, and a N3vf needle on the 2nd from the top side clip setting. Stock is 175 main, 50 pilot, and N3cw needle. I cleaned everything up and installed a 52 pilot. Being new to all this I wanted to take baby steps at first. I also re-adjusted the pilot air screw and idle.

I dont have anywhere to ride unless I go to state parks but I store the bike at my parents house and they have a couple acres I can ride on but its small and lots of trees(Boring). I probabaly putted around out there for 3-4 hours in low gears taking quite a few breaks. The bike seems to run a lil better and the plug isnt getting wet like before but still fairly dark/black. It also seems to smoke quite a bit less. I know im heading in the right direction just unsure if I do change something else whether I should drop down to a 50 pilot or swap out needles. I keep reading, how people say not to run your needle at the top or bottom adjustment though? Another part of me says just ride it cause its not fouling plugs like before.

[dan151]

yeah i went down in the main jet and kept to the pilot stock but i have 48 just incase it randomly fouls again. but i would ride it for awhile and bring a few estra plugs with u and see how it rides. if its good and doesnt foul, leave it alone and if it runs like shit and fouls drop the pilot or lean it out more