40:1 or 50:1?

[highrange101]

My 1997 RM 250 has new upper and lower with about 5hrs on it, I been running a 40:1 mix (yamalube) and its spitting oil all over the rear. I was told to try a 50:1 and see how that does, Is this wise on a complete rebuild? What is the least amount of oil per gal. can safely be used?

 

[mox69]

The proper way to correct this is to rejet the carburetor. Part of your carb is running rich.

Opinions vary on what is the "correct" gas:oil ratio. It has been shown that less oil isn't really any better for performance. I would go with whatever the service manual says , regardless of what the oil maker says.

 

[rmc_olderthandirt]

What mix was the bike set up before the rebuild?

If you are changing the oil mix to avoid another rebuild then you should check the carburetor jetting to make sure it is okay. Once you get the jetting set properly, stick with the oil/gas mix.

Rod

 

[daleao]

40:1 on the trail 32:1 on the track
I agree with the carb being to rich
check plug

 

[jason33]

change the silencer packing its probly soaked with oil- it will hold in more backpressure

40:1 lean out the jets 2 sizes,check the plug-- tan color is what you want- not black/or wet

 

[Mavrick70004]

def dont change the mix just to get rid of spitting oil that just fixes the side effect of a bad jetting, i would stick with daleao and run 40 or 32, more oil in the gas actually gives you better perofrmance since it allows the rings to seal better and get better compression

 

[Jeromeo]

would you rather seize a piston or Foul Plugs??? I would rather foul plugs.... pretty much any day than seize the piston. Like others have said Jet that sucker. Don't just change the ratio.

 

[showtime586]

I spun a main bearing on a KTM 250SX running Motul at 50:1.
I guess there is always the possibility that it was just coincidental bearing failure, but I have not run that ratio since.