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the 20:1 thread

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Trying this out starting today, I've heard many good things about this mix and the only bad thing I can think of is the price.


-Produces more slightly more power, helping the rings to seal better

-Lubricates the bottom end more

-Leans out the bike

My bike is jetted for 30:1 but it was still running rich. I have a kink in my pipe and I'm convinced that it's holding me back because even with my current jetting at my elevation I should be running lean for sure. At least according to the experts. Plugs are still black.

I have changed my flywheel oil seal, and my clutch side oil seal. New top end less than 10 hours ago with all new gaskets and such. So there are no oil or air leaks. Power valve was fully cleaned and functions properly, primary and auxilary ports are opening smoothly.

2005 yz250

45 pilot

165 main

JD Blue needle #1 clip position

Twin air filter

Stock pipe (slightly kinked in the front)

Shorty silencer

BR8EG Plugs (stock)

Stock #7 slide

3500-4000 ft

20 degrees celcius +

Using Castrol high performance dirt bike/motorcycle 2 stroke oil. This is the least expensive premix that I can find right now at 8$ a liter... I was hoping to find something for 4$ but no dice. I've heard good things about the castrol on this forum so it's not crap.

I still have a slight bog when snapping open the throttle, my buddy thinks it's my pipe cause his pipe got kinked and after he noticed a bog as well. Other than that with 30:1 and the #1 clip position the mid range and high end throttle run good but again plugs are still coming out black.

I'll keep this thread updated on any changes that I see with the new ratio and any changes I'll have to make to the pipe.

If anyone has their own experience with 20:1 post your results and opinions/facts!

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Started her up and just let her idle for about 5 minutes or so and there is a crapload more smoke here. Couldn't fully warm the bike up cause I don't want to take it up and down the block, but hopefully I'll take it out tomorrow!

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I've been running my son's bike at 24:1 but i'am using super tech oil, it only costs 11.00 a gallon.

His set up 2009 yz250

Hpbikes yz265 kit

FMF factory fatty, pc shorty

elvation is 1000ft

temps now around 85 to 100

48 pilot

stock needle in top groove

175 main

stock slide

NGK BR9EG spark plug

The bike runs perfect, no spooge and doesn't smoke after warm up.

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I remember as a kid that ALL two strokes ran on 20:1. Motorcycles, boats, even my dads lawnboy lawnmower. My dad always bought whatever oil was the cheapest.

The bikes were air cooled, steel lined cylinders, and did wear out. Still, I cannot remember anything oil related.

Now when you go to buy two stroke oil its almost like an advertisement. The bottles make a point of showing how oil lean they can be mixed. I saw some stuff at Auto Zone recommending 100:1. No mention of re-jetting on the bottle...

Getting back to today, I wonder how much of the oil technology and recommendations are environmentally based vs whats good for the engine?

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Well I took it out for only an hour today, didn't notice too much of a difference in power, mid and top felt good. I did notice less smoke btw, going to pull the plug here and put up a pic of it. Has idle time on it however, I'll have to do a real plug chop next time.

Was pouring rain and about 15 degrees out

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  • 1 month later...

These plugs are black after a wot run? My bike runs great but its plug still looks nasty if i randomly pop it out. It takes a little while at wide open before the plug looks respectable. Lol does your buddy hate you when you ride in front of him? I think my bike might asphyxiate anybody riding behind me at 20:1.

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I could see the need to run more oil with castor but i really dont see a point of any more than 32:1 with a %100 synthetic oil. DI equipped bikes (mostly snowmobiles) run as 100:1 at their lowest! It all depends on how well the motor is able to lubricate itself and how well the type of oil you use is able to withstand high stress operations

My bike has gone through 3 top ends. Every time I've run 32:1 Motul 800 and every time I was able to get my crosshatching back so its not like my cylinder is getting worn out. I've also checked the trace oil amount in the bottom end with every rebuild and always had good readings. I should probably mention that I mostly ride my bike at high rpms at the track/open desert and its jetted pretty close to spot on.

Its not to say that you are hurting your motor but we've progressed far enough that our motors don't need such a large amount of oil anymore due to the higher grade oils available and better lubrication from the motor itself. If you are doing this just to see if the 20:1 gives a noticeable increase in power then go for it but i doubt it would be anything significant, there will however be a more significant change in the weight of your wallet.

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I have had many two strokes, all the way back to the 70's. I run 50:1 in all my two strokes (including my chain saw and my TM 300) I must say though my jetting is real close to spot on.

Unless you are jetted REAL LEAN I don't think you will hurt it.

If you run 40:1 or more I think you will plug up your powervalve and the packing in your muffler.

Now I ride four stroke mostly.

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c_dasilva127 nd live 2 ride are correct. 20:1 IS RICHER then say 32:1. 20 parts gasoline to 1 part oil aside from 32 parts gasoline to 1 part oil. its much richer in fact.

They are referring to the fact that as you add more oil to the fuel your air/fuel ratio effectively becomes leaner as their is a larger percentage of oil per unit of fuel.

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Typically a bog when wacking it open is due to a lean condition on the needle and/or pilot and air screw.

Trying turning the air screw in half a turn and see if the bog goes away.

A stutter more accurately represent a rich condition. The stock yz250 is definately on the richer side of the needle than the leaner side...

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Anytime an engine gets less gas, it is running leaner. If you put more oil in the gas, there is less gas because of the oil, going through the jets.

not true, run a 2 stroke at a 1:1 ratio and tell me what happens? your bike does not run uncontrollably lean, it wont even run because of the saturation of oil in your mixture.

As far as jets are concerned, yes the less gas being put into the engine the leaner it runs, but when it comes to oil mixture, the less saturated the fuel is with oil, the more volatial it becomes.

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Could you explain your thought process a little better?

Lean and Rich descriptors for Air/Fuel Ratio refer to amounts. The oil used for lubrication effects the amount of gasoline in a mixture. From what I can tell you didn't disprove anything he said. You're trying to imply that you can be leaner with more gas as that would make what he said "not true". Less oil resulting in more volatile leading to vaporization and flash point? That doesn't have anything to do with the amount of gasoline or air in the mixture.

Perhaps I don't understand

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