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Luca Devera

YZ125X Is my bike to rich?

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I recently added a touch of extra oil to my gas. The bike has fouled 3 plugs in the last 4 days, bike feels fine and doesn't smoke too much. I'm not sure what to do next, should I drain my tank and add a more lean mixture? Here is what my plug looks like:1247463414_IMG_61341.thumb.JPG.b9a03d91b04cc2cbee3be22644d8b821.JPG

Edited by Luca Devera

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You went from what?  40 to 32?  How are you jetted now?  Altitude and temp?  Same premix?  What's your plug gap and temp range?

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Adding more 2 stroke oil actually leans the fuel mixture. Jetting changes are what you need to research and learn. Stick to the 32 ratio and change jets. Fouling plugs is jet related settings for your location and type of riding...

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Float level a tad too high (they are set that way from the factory) and,

as other have suggested, probably too rich jetting on the pilot and needle circuits for your specific usage.

 

Brand of premix oil used? (ideally not a 'racing' oil if you are trail riding at moderate rpms)

Exact usage?  (mostly slow/technical trails or, faster off-road / sustained high rpms etc.)

Engine hours?  (if excessive can be low compression etc.)

 

Edited by mlatour

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4 hours ago, TommyCrown said:

Adding more 2 stroke oil actually leans the fuel mixture. Jetting changes are what you need to research and learn. Stick to the 32 ratio and change jets. Fouling plugs is jet related settings for your location and type of riding...

Serious question: How does adding oil lean out the gasoline? Correct me if I am wrong but, the closer to a 1:1 ratio, the RICHER you get. The further away from a 1:1 ratio, the LEANER you stay.

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2 hours ago, Emad GB said:

Serious question: How does adding oil lean out the gasoline? Correct me if I am wrong but, the closer to a 1:1 ratio, the RICHER you get. The further away from a 1:1 ratio, the LEANER you stay.

The more oil you add to the gasoline, the thicker the mixture gets, thus it has a harder time going through the jets, causing the leanness described.

Sure, the oil ratio gets RICHER, but the air/oil mix going into the engine ends up being leaner.

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more oil in gas = leaner

A jet hole is a fixed size, meaning the amount of liquid that passes through does not change. Oil doesn't burn like gas, so when you add more oil, less gas passes though the jet at a given time. This gives less burnable fuel for the same amount of air going into the carb. FUEL to AIR ratio is leaner. 

People use the word "richer" to describe increasing the amount of oil in premix, which is confusing.  

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13 hours ago, Luca Devera said:

The bike has fouled 3 plugs in the last 4 days, bike feels fine and doesn't smoke too much.

Always worth trying fresh premix. Just to be sure. Hopefully not a fuel supplier issue.  Beware that stock jetting wont work everywhere. Worn piston or rings or a clogged air filter will impact jetting too.  

Edited by numroe

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10 hours ago, mlatour said:

Float level a tad too high (they are set that way from the factory) and,

as other have suggested, probably too rich jetting on the pilot and needle circuits for your specific usage.

 

Brand of premix oil used? (ideally not a 'racing' oil if you are trail riding at moderate rpms)

Exact usage?  (mostly slow/technical trails or, faster off-road / sustained high rpms etc.)

Engine hours?  (if excessive can be low compression etc.)

 

I use Yamalube, I trail ride so half the time I'm slow and half the time I'm full throttle, about 10 hours on the bike

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From your description, I'd start by going with a one step leaner pilot jet,

setting the needle clip one notch higher (lowering the needle)

and, setting the float level 1mm lower.

Unlike an MX race track's relatively short straightaways, if you off-road usage also included some sustained rpm road / open terrain riding, 

I'd also preventively enrich the main jet by one size, maybe two if the terrain is hilly.

 

The silencer's packing is probably oil soaked as well otherwise it will continue to spooge/ drip even after you find the perfect carb settings.

 

Edited by mlatour
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12 hours ago, MANIAC998 said:

The more oil you add to the gasoline, the thicker the mixture gets, thus it has a harder time going through the jets, causing the leanness described.

Sure, the oil ratio gets RICHER, but the air/oil mix going into the engine ends up being leaner.

Ohh ok. Thank you!

11 hours ago, nokturnal said:

more oil in gas = leaner

A jet hole is a fixed size, meaning the amount of liquid that passes through does not change. Oil doesn't burn like gas, so when you add more oil, less gas passes though the jet at a given time. This gives less burnable fuel for the same amount of air going into the carb. FUEL to AIR ratio is leaner. 

People use the word "richer" to describe increasing the amount of oil in premix, which is confusing.  

Thank you!

Edited by Emad GB
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17 hours ago, Emad GB said:

Serious question: How does adding oil lean out the gasoline? Correct me if I am wrong but, the closer to a 1:1 ratio, the RICHER you get. The further away from a 1:1 ratio, the LEANER you stay.

Think of it this way. If you add more Cokacola than Rum when mixing a drink, is there less alcohol per volume now? The coke is your premix and the rum is your fuel. That’s how you go lean on the fuel to air ratio when you add too much premix. 

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On 4/7/2021 at 6:04 PM, Luca Devera said:

I was at 32 not sure what I'm at now I just added a touch of extra oil to my gas can. Stock jetting 

Why did you do that ? Seriously . The bike ran good and ....? Did you just decide a little more oil would lubricate better or what ? If you were running 32 -1 and everything was good ...dump whatever you have in there now and mix up 32-1 and leave it alone . 

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On 4/7/2021 at 5:15 PM, Luca Devera said:

I recently added a touch of extra oil to my gas. The bike has fouled 3 plugs in the last 4 days, bike feels fine and doesn't smoke too much. I'm not sure what to do next, should I drain my tank and add a more lean mixture? Here is what my plug looks like:1247463414_IMG_61341.thumb.JPG.b9a03d91b04cc2cbee3be22644d8b821.JPG

If your bike is rich, it would be a Husqvarna .

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On 4/8/2021 at 10:15 PM, Crustybutt said:

Why did you do that ? Seriously . The bike ran good and ....? Did you just decide a little more oil would lubricate better or what ? If you were running 32 -1 and everything was good ...dump whatever you have in there now and mix up 32-1 and leave it alone . 

I though my plug look rich, your right I should have just left it alone. 

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2 hours ago, Luca Devera said:

I though my plug look rich, your right I should have just left it alone. 

I'll make a suggestion . Get a manual first thing . There's a lot more than just gas/oil ratio in getting a bike to run right . Oddly enough , adding oil to to existing mix will lean it out ...but just slightly . The real solution is in jetting and overall condition of the engine . 

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