Hey all, i have a 2001 yz 250 2t and i keep fouling plugs every half tank of gas. Ive tryed 32:1 40:1 and even 50:1 and they all come out failed. It has stock jettiting and everything and i cleaned carb and airfilter. The pipe has no packing in it. It dosent even have a core in the exhaust to repack so i orderd a pro circuit silencer. Do you guys think the exhaust is the problem or something else? The plugs come out really wet and black. I run br8es
Fouling Plugs
- Thread starter smerch69
- Start date
The carburetor is too rich for your altitude/temperature. Your AIR/FUEL mix is too rich.
Which is not the same as the premixed oil ratio. In fact leaning your OIL/FUEL ratio actually RICHENS your AIR/FUEL ratio.
Brass jets become worn over time which makes them richer and richer as time goes on. You either need to replace the worn jets or install smaller jets if the stock ones are new.
Whatever you do, pick a oil mix ratio and stick with it. Changing premix ratios is very dangerous and leads you in circles when trying to diagnose a fueling issue.
-BIG DAN
Which is not the same as the premixed oil ratio. In fact leaning your OIL/FUEL ratio actually RICHENS your AIR/FUEL ratio.
Brass jets become worn over time which makes them richer and richer as time goes on. You either need to replace the worn jets or install smaller jets if the stock ones are new.
Whatever you do, pick a oil mix ratio and stick with it. Changing premix ratios is very dangerous and leads you in circles when trying to diagnose a fueling issue.
-BIG DAN
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The carburetor is too rich for your altitude/temperature. Your AIR/FUEL mix is too rich.
Which is not the same as the premixed oil ratio. In fact leaning your OIL/FUEL ratio actually RICHENS your AIR/FUEL ratio.
Brass jets become worn over time which makes them richer and richer as time goes on. You either need to replace the worn jets or install smaller jets if the stock ones are new.
Whatever you do, pick a oil mix ratio and stick with it. Changing premix ratios is very dangerous and leads you in circles when trying to diagnose a fueling issue.
-BIG DAN
My elevation is around 1400ft. I dont really understand jetting so what would be good for my elevation? Tempature when riding is 20-30℃ depending on the day. I live in northwestern ontario. And what would you reccomend for a premix ratio? I do mx but i like to putt around trails too. Not always on the pipe
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Some reading for you. http://www.iwt.com.au/mikunicarb.htm
So, 'STD' is short for 'Standard' or 'Stock.' Typically whatever the Original Equipment Manufacturer (OEM) intended for production models.
I think 32:1 is a universal starting place for Fuel/Oil mixture. (Premix Ratio)
When talking about the bike running rich or lean, you are referring to the Air/Fuel Ratio.
They recommend (With an Aftermarket pipe installed) a Main Jet 175, Pilot Jet 45, stock slide and needle settings, idle air screw at one turn from gently seated.
Give it a try and report back. -BIG DAN
So, 'STD' is short for 'Standard' or 'Stock.' Typically whatever the Original Equipment Manufacturer (OEM) intended for production models.
I think 32:1 is a universal starting place for Fuel/Oil mixture. (Premix Ratio)
When talking about the bike running rich or lean, you are referring to the Air/Fuel Ratio.
They recommend (With an Aftermarket pipe installed) a Main Jet 175, Pilot Jet 45, stock slide and needle settings, idle air screw at one turn from gently seated.
Give it a try and report back. -BIG DAN
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Will do but i need to get a new plug cause mines fouledSome reading for you. http://www.iwt.com.au/mikunicarb.htm
So, 'STD' is short for 'Standard' or 'Stock.' Typically whatever the Original Equipment Manufacturer (OEM) intended for production models.
I think 32:1 is a universal starting place for Fuel/Oil mixture. (Premix Ratio)
When talking about the bike running rich or lean, you are referring to the Air/Fuel Ratio.
They recommend (With an Aftermarket pipe installed) a Main Jet 175, Pilot Jet 45, stock slide and needle settings, idle air screw at one turn from gently seated.
Give it a try and report back. -BIG DAN
If the jets in the carburetor are the correct size, or at least close, I would point you to crank seals. Specifically the clutch side.
Usually you can smell the terrible transmission fluid burning and it'll smoke uncontrollably, especially after sitting overnight. If it smells like shit and smokes, I would say crank seals.
-BIG DAN
Could be why you have no packing in the muffler... it got soaked in trans fluid and the previous owner chucked it.
Usually you can smell the terrible transmission fluid burning and it'll smoke uncontrollably, especially after sitting overnight. If it smells like shit and smokes, I would say crank seals.
-BIG DAN
Could be why you have no packing in the muffler... it got soaked in trans fluid and the previous owner chucked it.
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If the jets in the carburetor are the correct size, or at least close, I would point you to crank seals. Specifically the clutch side.
Usually you can smell the terrible transmission fluid burning and it'll smoke uncontrollably, especially after sitting overnight. If it smells like shit and smokes, I would say crank seals.
-BIG DAN
Well it only smokes when it warms up, like when im ridin it dosent "roll coal" like a deisel truck would (except it would be blue smoke)
No noticeable transmission fluid loss?
Typically, you'll know it when you're burning transmission oil due to a right seal failure.
If the left seal fails it'll be hard to start and very lean. Worst case scenario, it will lean seize the engine due to the extra air coming in. But you are having the opposite issues.
If all else fails, the crank seals are external to the cases. Nothing but a couple hours to get it done. -BIG DAN
Typically, you'll know it when you're burning transmission oil due to a right seal failure.
If the left seal fails it'll be hard to start and very lean. Worst case scenario, it will lean seize the engine due to the extra air coming in. But you are having the opposite issues.
If all else fails, the crank seals are external to the cases. Nothing but a couple hours to get it done. -BIG DAN
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