yz125 clutch

[mritch8]

I just got a yz 125 and took it for a ride yesterday, it sounds wants to stall every time I try to go even though the rmp's are pretty high and im only coming out of first gear. Its pretty much impossible to start out in second without the bike bogging down. Is this a problem with technique or my bike. BTW im letting the clutch out slow and by the end of the day I started just letting it out halfway then pull it back then letting it go but i feel that might be bad for the bike. if you have any suggestions or tips for how to prevent this please let me know 

[ossagp]

It could be you or a bike in need of tuning.   Do you know the symptoms of rich running engines or lean running engines?   Smoking a lot (hard term there if you are not used to what "a lot" is I know) is rich,  lean is "clean" if you like rhymes.  Once under way, how does the bike run?  Can you describe how the business end of the spark plug looks?  Ie color, wet,  dry,  clean,  fuzzy etc.  A picture is even better.

 

Because if the bike is in good running condition,   and it sounds like the clutch works good enough to kill the engine (isn't slipping in other words) then it is your technique.   I am assuming the clutch is adjusted to where it has a little play in the cable.  

[mritch8]

2 minutes ago, ossagp said:

It could be you or a bike in need of tuning.   Do you know the symptoms of rich running engines or lean running engines?   Smoking a lot (hard term there if you are not used to what "a lot" is I know) is rich,  lean is "clean" if you like rhymes.  Once under way, how does the bike run?  Can you describe how the business end of the spark plug looks?  Ie color, wet,  dry,  clean,  fuzzy etc.  A picture is even better.

 

Because if the bike is in good running condition,   and it sounds like the clutch works good enough to kill the engine (isn't slipping in other words) then it is your technique.   I am assuming the clutch is adjusted to where it has a little play in the cable.  

yes the clutch has a little play, and if anything its running rich because there is a good amount of smoke and the guy i got it from said he ran it a little over 50:1, I will check the plug when i get home. the bike seems like it sputters a little in low rpm's is that normal? and also what premix and engine oil should i use?

[ossagp]

The oil ratio has zip to do with the type of rich that I am referring to.   The kind i am referring to is mainly jetting and float related.   The sputtering sounds rich to me.  Check the plug and get back with us.   What year do you have by the way?  FYI my 125 yz's live on Yamalube at 20-1 but don't think about changing that at this point.   Lets get you launching it good first.  

[Max17]

Pre-mix ratio depends a lot on which oil you use.  Some should be at 20:1 others at 50:1, 80:1, 100:1, or even 200:1.  I used to run Amsoil Saber or Eliminator at 50:1 and then at 80:1 but for the past 2 years it's been Opti 200:1 at 100:1 for all our 2-strokes with zero problems and little wear.

ossagp is mostly correct that your air:fuel mixture ratio isn't the same as you gas:oil pre-mix ratio.  The former is about increasing or decreasing the amount of air relative to fuel in the flow from the carb into the cylinder.  Rich is when there is too much fuel (gas & oil) relative to the amount of air making up the total volume and lean is the opposite.  As ossagp correctly states, pre-mix ratio alone does not itself determine whether the bike is running rich or lean; that is controlled by the sizes of the jets in the carb for how much mixed fuel they let into the airflow on its way to the cylinder.  For the same pre-mix ratio, bigger jets will flow more fuel and there make the charge entering the cylinder richer while smaller jets will add less fuel of the same pre-mix ratio and cause the change to be leaner (more air in the total volume than for rich).

The slightly tricky part i that pre-mix ration can affect your rich/lean condition IF THE JETS ARE KEPT THE SAME.  Increasing the amount of oil in the pre-mix (say for example going from 50:1 to 20:1 {fewer parts of gas with the same amount of oil} actually makes the bike run leaner, not richer, because there is less gas content in the gas/oil mixture and therefore less gasoline in the ail/fuel mixture that results from the same volume of mixed fuel mixture being added to the air.  It's counter-intuitive at first that adding oil makes the result leaner but it's because adding oil reduces gasoline.

ossagp's point is forget about the pre-mix ratio for now (unless you have some other reason to change it) and find  the correct jetting for that fuel mix.  Remember that ambient air temperature and altitude can also require jetting changes for the same fuel mixture.  Luckily, non-racers riding in similar areas in the same season won't notice a big enough variation to bother changing jetting on a frequent basis.  EFI and Lectron carbs to an extent remove the need for rejetting once the initial correct settings are set.

 

[mritch8]

9 hours ago, ossagp said:

The oil ratio has zip to do with the type of rich that I am referring to.   The kind i am referring to is mainly jetting and float related.   The sputtering sounds rich to me.  Check the plug and get back with us.   What year do you have by the way?  FYI my 125 yz's live on Yamalube at 20-1 but don't think about changing that at this point.   Lets get you launching it good first.  

ok thanks thus helps alot, im going riding tmro but have to mix more gas and dont have access to yamalube, im only going to go to my local auto zone or walmart, what type of oil would be ok to run from there?

[ossagp]

Man,  I don't even know what they have.  I wouldnt change mixes and definitely not to my mix until you have the float etc figured out.  You CAN'T cure something over rich enough to make it sputter by adding oil,  no matter what the "you might seize it if you go to a richer oil fuel mix" crowd says.    Lucas products seem pretty good if they have that,   stick to something in the recommended range like 30-32 to one if you are going to change.  

[michaelchristie207]

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