gas mix ratio

[matt_12345]

Hey when i bought my Rm 250 the guy i bought it off mixed it at 50:1 and i have been mixing it at that with no problems but everyone says 32:1 and the book says 32:1. did he do somehting to it so it would run fine at such a lean mix without burning up or what??

 

[FruDaddy]

Maybe he jetted it to run at 50:1, if you change the mix you ,ay have to change the jetting as well. Ask the previous owner how often he fouled plugs, and how frequently he replaced the top end. Then get back with us. In the meantime, search for mix ratios and read up.

 

[griffbones]

At 50:1 it is running richer than at 32:1 unless he re-jetted the bike for the 50:1 mix ratio.

 

[matt_12345]

hey guys... im pretty sure he must of jetted it to run like that because he knows what hes doing i still tlak to him sometimes.. he did the top end every 3 quarts of oil. gave me a bunch of pistons to prove it. what do u have to change in the jetting to run it that lean.. do u make the main jet larger to richen it up??

 

[IndyMX]

hey guys... im pretty sure he must of jetted it to run like that because he knows what hes doing i still tlak to him sometimes.. he did the top end every 3 quarts of oil. gave me a bunch of pistons to prove it. what do u have to change in the jetting to run it that lean.. do u make the main jet larger to richen it up??

For the millionth time, LEAN / RICH have nothing to do with the OIL to FUEL ratio.

LEAN / RICH have to do with the AIR / FUEL ratio.

Like Rich Rohrich has said on here, you can run at 16:1 premix and still run fine, so long as it's jetted properly.

Running 50:1 is probably not such a good idea, but if you didn't rejet from stock, you'd be running extremely rich.

Unless the original owner was running oil that was designed to run at a 50:1 mix, I wouldn't suggest it. That's just not enough oil to properly lubricate the bottom end.

 

[N3WFI3]

run 40:1 with a good oil and you should be ok

 

[destructo]

Remember, the only lubrication your crank recieves is from the oil in your gas, I have never gone wrong with 32:1. My KX 125 had been run before I got it at 50:1 luckily with only about 10 hours on a Wiseco topend, all I had to do with the jetting was open the air screw out about a turn and adjust the idle up, runs absolutely perfect and fricken ripps, very crisp all the way to topend.

 

[matt_12345]

My rm also has an fmf fatty pipe with shorty silencer if i was to follow thier suggested jetting specs should i go back to the 32:1 mix.. does anyone know if there suggested specs r good i live in NS canada int he valley so im pretty much at sea level.

 

[destructo]

I have found that stock jetting specs at sealevel are a pretty good baseline, usually slightly rich, usually on bottom end, which is not a bad thing. If you go back to stock jetting, 32:1 is good to go, every time ive installed an FMF exhaust ive had to drop down one pilot jet size from stock.

 

[mxrider992]

in my opinion, 50:1 is way too lean a gas:oil ratio if u want longevity. i run 40:1 on motul synthetic and my bike runs great. i would suggest 40:1 of full synthetic