I have a 04 yz 125 and it keeps fouling plugs one will last about an hour or two at max.they seem to be covered in oil which means that its to rich but is that the the problem that i have to lean my bike settings or what do i do im so confused do i re jet my bike was never jetted and where at 6500 ft above sea level.or could it be to much oil in the gas. so can anyone help me please.I almost had a heat stroke tying to push my bike back from 110 deggrees when my plug fouled.I would really like to ride my bike again.
Fouling plugs help yz 125
- Thread starter YZ125jk
- Start date
Be patient. Most of work all day and don't have the luxury of sitting glued to the computer screen all day waiting to answer your question.
Your bike is running way to rich. Sounds hot there. The hotter it gets, the more you need to lean out your jetting. Try looking up some jetting discussions in the 2 stroke forum. http://dirtrider.net/forums3/showthread.php?t=42618 They are very thorough in thier explanation and diagnosis of jetting related problems.
Good luck
Your bike is running way to rich. Sounds hot there. The hotter it gets, the more you need to lean out your jetting. Try looking up some jetting discussions in the 2 stroke forum. http://dirtrider.net/forums3/showthread.php?t=42618 They are very thorough in thier explanation and diagnosis of jetting related problems.
Good luck
- Thread starter
- #7
usaully my bike takes about 20 kicks till it starts then i just went and twisted my pilot screw all the way closed and turned it twice.when i was closing the screw it took about 4 or 5 twists I think my dad set it was to rich thats why it was fouling and not starting.then after that i kicked it once with no throttle and it started right up.And do u think that i have to re-jet my bike.were at 6500 ft abs and its set at stock.The problem is im only 14 and im not sure if I could do that by myself.But then i dont feel like taking it to the shop and paying $100 to get it jetted when i know how but scared to do it.Im just scared im really gonna mess somthing up.
I know the feeling well bud. It is in your best interest to spend the money on a repair manual for your bike. It will go into extreme detail about how to do a lot of this stuff. Make sure you get the manufactors repair n rebuild manual. I have found that it's worth the extra 10 bucks than buying an aftermarket one. And yes. I think at 14, a rejet is within your capabilities. It's really not that hard when you got the manual beside you with the pics and instructions. Don't forget to read the jetting stickys on the 2stroke forum for some members experiences.
nikki
Moto Junkie
- Apr 21, 2000
- 5,802
- 1
I know this seems simple... but what plug are you running? The stock BR9EG? Try a BR8ES. It's a hotter plug.... for some reason, YZ125's seem to do better with 8 heat range plugs.
Now back to your air screw... when you turned the screw all the way in, how far did you turn it out to get the bike to idle/run/rev nicely? One full turn = 4 clicks = the flat part of the screw where you put your screwdriver doing a full turn. If it's more that 2 full turns out, you can go to a smaller pilot jet (leaner) as the bike runs better with more air. Because of your altitude, the air is thicker and it's harder for the bike to get air compared to fuel, so that's why it's running rich.
I'm pretty sure your stock pilot jet is a Mikuni 25. You can loosen the screws on the two clamps on the carb and twist your card so you can get to the nut at the bottom. Take this nut off (it's a 17mm I think - watch out for the gas that will drain from the float bowl), then use a small flat head screw driver to remove the pilot jet (you'll see it in there, it's a long skinny jet to the side, the middle one is the main jet). The Mikuni pilot's go by 2.5, so you can try a 22.5 or 20.0 which are the next two sizes leaner. The jets are like $5 each. Make sure to re-tune your air screw with each jet change and try it out.
Hope this helps a little.
Now back to your air screw... when you turned the screw all the way in, how far did you turn it out to get the bike to idle/run/rev nicely? One full turn = 4 clicks = the flat part of the screw where you put your screwdriver doing a full turn. If it's more that 2 full turns out, you can go to a smaller pilot jet (leaner) as the bike runs better with more air. Because of your altitude, the air is thicker and it's harder for the bike to get air compared to fuel, so that's why it's running rich.
I'm pretty sure your stock pilot jet is a Mikuni 25. You can loosen the screws on the two clamps on the carb and twist your card so you can get to the nut at the bottom. Take this nut off (it's a 17mm I think - watch out for the gas that will drain from the float bowl), then use a small flat head screw driver to remove the pilot jet (you'll see it in there, it's a long skinny jet to the side, the middle one is the main jet). The Mikuni pilot's go by 2.5, so you can try a 22.5 or 20.0 which are the next two sizes leaner. The jets are like $5 each. Make sure to re-tune your air screw with each jet change and try it out.
Hope this helps a little.
- Thread starter
- #12
O yeah i forgot to say that theres this one screw on my carbuator that i messed with accidently.its on the left side and has a bolt and screwdiriver head to twist in or out does anyone know what this is?I kinda tweaked it a little because i thouht that,that screw was the pilot jet.i did this about 2 months ago.
I'm riding a 2003 yz125, stock main is 410, stock needle is in the 3rd clip, stock pilot is a 40.
Not sure about the '04, but mine wouldn't idle and fouled plugs all the time, and they were oil soaked, i dropped the needle to the second clip and put a 380 main in, and it ran perfectly.
If you're at 6500ft you're at about colorado altitude, when jetting my bikes i always go down 8% on the stock main and drop the needle one clip from stock, and use that as a baseline to start from, sometimes it makes the bike run perfect, other times it requires a lil' fine-tuning from there. Check your owners manual for the stock settings and go from there. just my $.02
Not sure about the '04, but mine wouldn't idle and fouled plugs all the time, and they were oil soaked, i dropped the needle to the second clip and put a 380 main in, and it ran perfectly.
If you're at 6500ft you're at about colorado altitude, when jetting my bikes i always go down 8% on the stock main and drop the needle one clip from stock, and use that as a baseline to start from, sometimes it makes the bike run perfect, other times it requires a lil' fine-tuning from there. Check your owners manual for the stock settings and go from there. just my $.02
it's easiest of you take the tank and subframe off just to have more room to work with, but it isn't required.
Their are two bolts on the top of the carb, they are way to tight from the factory as machines put them on there, if you try and use a screwdriver you will strip them, grab some vise-grips and break the seal first. then just pull the slide out, slide the spring up and un hook the throttle cable(it helps to unhook the cable from the throttle tube on the bars so you can pull a bit more slack in the cable by the slide.) then there's is a 6mm nut where the cable was attached, undo that and you will see the needle, move it to the second clip and put it all together again, make sure the plastic groove on the end of the spring gets seated on the groove on the nut holding the cable down, and you should be good to go.
Their are two bolts on the top of the carb, they are way to tight from the factory as machines put them on there, if you try and use a screwdriver you will strip them, grab some vise-grips and break the seal first. then just pull the slide out, slide the spring up and un hook the throttle cable(it helps to unhook the cable from the throttle tube on the bars so you can pull a bit more slack in the cable by the slide.) then there's is a 6mm nut where the cable was attached, undo that and you will see the needle, move it to the second clip and put it all together again, make sure the plastic groove on the end of the spring gets seated on the groove on the nut holding the cable down, and you should be good to go.
