My engine has just been rebuit with a new bottom, rebore/plate and piston. My mechanic has told me to run at 50:1 (200cc/ 5 litres) after two tankfuls at 32:1. I see from most posts, that the general opinion is to run around 32-40:1. I don't race my bike, I just ride through the woods with the occasional flat out fire road. I'd like to get a bit of life out of an expensive rebuild before having to stump up cash too quickly. What do you all reccomend ?
Will 50:1 kill my bike ?
- Thread starter sherrif
- Start date
I assume you are refering to your KX250. If you're not going to be screaming the engine, 50:1 won't kill your engine. In anycase, I'd run 32:1 for the extras lubrication that it gives. Up to 40:1 in a 250 is OK.
Be aware that changing the oil ratio will affect jetting so what ever you decide on, stick with it.
Be aware that changing the oil ratio will affect jetting so what ever you decide on, stick with it.
Moto Squid
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- Jul 22, 2002
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I run Amsoil @ 42:1 with no complaints in my 125, which the motor takes a beating when racing
WorldWideRacer
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- Jul 12, 2000
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50:1 may not kill your bike, it depends on the way it is jetted and your riding style. But hey, if you put only 1.5 quarts of top-grade synthetic oil in your car engine and baby it, I bet that would last for a while also. :)
Running a richer oil ratio has many benefits, and in my experience, dramatically increases top-end component life. On a 125, run between 25:1-35:1. On a 250, run 30:1-40:1. Lubrication is one thing you dont want to skimp on in a high performance machine.
Running a richer oil ratio has many benefits, and in my experience, dramatically increases top-end component life. On a 125, run between 25:1-35:1. On a 250, run 30:1-40:1. Lubrication is one thing you dont want to skimp on in a high performance machine.
I tell you what... I use what Motul recommends for its 800 2T Racing oil, which is
66,7 : 1 (1.5% or 150ml of oil for every liter of gas)
and never dah any problems at all. This is the forth bike I did it (YZ 125, KX 125, KDX 250 and now RM 250). It is true that I never ride like RC, but more like MC, technically and smooth (that's what my Mom says)...
66,7 : 1 (1.5% or 150ml of oil for every liter of gas)
and never dah any problems at all. This is the forth bike I did it (YZ 125, KX 125, KDX 250 and now RM 250). It is true that I never ride like RC, but more like MC, technically and smooth (that's what my Mom says)...
jmics19067
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- Jan 22, 2002
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going from 50 to 1 to 42 to one would probably make your bike smoke less actually. If your bike didn't smoke before at 50 to one it is possible that you will have to go up on the jets and down on the clip. What happens when you add more oil to your mix is that you are making the gas thicker and therefore can't flow thru the carberator as easily. I would run 32 to one simply because one 16 oz bottle to 4 galls of gas.
Do yourself a favor, do a search and read all of the different posts about jetting you can.
Do yourself a favor, do a search and read all of the different posts about jetting you can.
Not quite. When you add more oil to the gas there is less gas for the same volume of the gas/oil mixture. This means less gas in the air/fuel mixture which makes for a lean burn in the combustion chamber.
Excellent advice :)
jmics19067
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True. Thanks for pointing that out .
Maybe a combination of both? If your jetting recquirements can change with the specific gravity of the fuel ,wouldn't the specific gravity change with the premix ratio changes? double indemnity?
Any how Sherrif richer oil /gas premix = leaner fuel/ air mixture. That much I know is true. Although I am still learning the whys and hows.
But isn't the combination of gas and oil considered fuel and the volume of fuel going into the combustion chamber the same whether it is 20:1 or 40:1. The "fuel" to air ratio is the same right regardless of the gas/oil ratio? Thats the "jets" part to control the air/fuel ratio. The oil burns too right? Maybe not as explosively as the gas but still it burns.????? I can't see how adjusting the oil/gas ratio effects the air/fuel ratio.. I have a half a liter of gas and half a liter of air totaling one liter...the same as saying a quarter liter of oil a quarter liter of gas and a half liter air still totaling one liter...
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I'm about ready to get in over my head so when I get a chance I'll do a search on this. It's been discussed before.
I did some searches but couldn't find the ones that discussed how much the buring oil adds to anything.
James,
There is a fourm that has "good" threads that have been nominated to be there. But even they are somewhat fragmented like you say. I like the idea of a place to go that awnsers questions that come up over and over again. Most of the time users are just lazy or don't understand how to use the search. May Okie will set something up in his "spare" time
James,
There is a fourm that has "good" threads that have been nominated to be there. But even they are somewhat fragmented like you say. I like the idea of a place to go that awnsers questions that come up over and over again. Most of the time users are just lazy or don't understand how to use the search. May Okie will set something up in his "spare" time
:think: That's weird! I just read your post and now it's an "X"
jmics19067
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- Jan 22, 2002
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This is what I think/understood I have read and believe to be true.
specific gravity of the fuel will change jetting recquirements. <among a host of otherthing s that recquire jetting for>.
that and when your premixed fuel/ air gets into the bottom end of your two stroke engine the oil drops out of the mixture.
when you take apart the engine there is usually/should be a puddle of oil in the bottom that contains very little gas in it.
now this part is pure conjecture on myself
that if the specific gravity of the fuel is heavier it is harder for the airflow going thru the carb to pick up what it needs. needing richer jetting
And as the oil drops out there is less gasoline <from the more oil in the gas premix>in the fuel mixture , recquiring richer jetting.
now whatever oil that drops out of the mixture and gets splashed/ sucked up into the combustion chamber does burn, but not really as a part of the the airfuel power producing combustion process, but more like an after the fact built in incinerator . So I believe the original statements of RM guy and I are both right together but not correct separately.
If BWalker,Jaybird and /or Rich Rohrich care to step in and tried to straighten us out I am sure we would get the correct answer if we can understand it :eek: .
This discussion would actually probably be better off in the advanced technology forum on the hows and whys these things work. The bottom line is basicly that if you add more oil to your gas you will need bigger jets in your carb if it was jetted correctly from the beginning.
On the amount of oil you should use in your gas from what I understand should be within the parameters what the oil manufacture suggests. if the brand of oil you use says you can go to 50 -1. I would assume you would be adequately protected at 50-1. Or atleast as protected as the oil manufacture thinks is ok. High rpms , High temparatures and/or constantly high loads calls for more oil then less.
specific gravity of the fuel will change jetting recquirements. <among a host of otherthing s that recquire jetting for>.
that and when your premixed fuel/ air gets into the bottom end of your two stroke engine the oil drops out of the mixture.
when you take apart the engine there is usually/should be a puddle of oil in the bottom that contains very little gas in it.
now this part is pure conjecture on myself
that if the specific gravity of the fuel is heavier it is harder for the airflow going thru the carb to pick up what it needs. needing richer jetting
And as the oil drops out there is less gasoline <from the more oil in the gas premix>in the fuel mixture , recquiring richer jetting.
now whatever oil that drops out of the mixture and gets splashed/ sucked up into the combustion chamber does burn, but not really as a part of the the airfuel power producing combustion process, but more like an after the fact built in incinerator . So I believe the original statements of RM guy and I are both right together but not correct separately.
If BWalker,Jaybird and /or Rich Rohrich care to step in and tried to straighten us out I am sure we would get the correct answer if we can understand it :eek: .
This discussion would actually probably be better off in the advanced technology forum on the hows and whys these things work. The bottom line is basicly that if you add more oil to your gas you will need bigger jets in your carb if it was jetted correctly from the beginning.
On the amount of oil you should use in your gas from what I understand should be within the parameters what the oil manufacture suggests. if the brand of oil you use says you can go to 50 -1. I would assume you would be adequately protected at 50-1. Or atleast as protected as the oil manufacture thinks is ok. High rpms , High temparatures and/or constantly high loads calls for more oil then less.
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