2004 CR250r 2-stroke oil mix HELP

i've just gotta ask...31:1? why an odd number?

Micahdawg said:

Another vote for 32:1. I used to run higher...around 38:1 on my Rm250. I since went to 32:1 and my plug still looks great.

In all of my searching, I have discovered that generally 32:1 is good for 250's and 24:1 for 125's.

Micah

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I totally agree with that. Jeremy McGrath was running 32-1 when he was with yamaha. Why would I need to go any leaner than this.

The reality is that you can run anything from 30:1 - 65:1 provided that you are using a full synthetic (depends on how much you want to blow out your pipe). Motul recommends that you run 50:1 with their 800 synthetic oil if you are in WFO racing situations but you can go leaner on the oil if you're not pushing it that hard.

Just keep in mind that the more oil you mix into your gas, the leaner a air/gas mixture you're providing the motor so you want to be careful with your jetting so you don't seize the engine.

this topic has been debated to death. It's not unlike debating whether smoking will shorten your lifespan.

If nothing else, we have to question why the factories would suggest anywhere from 20:1 to 32:1?

Common sense tells us that less oil in the mix will provide less lubricant for the bearings and cylinder. Regarding the comment that the engine internals still looked good after 6 races, gosh, I would hope so! That's barely broken in! I generally do a top end on a 250 once per season, on the last engine I rebuilt the ring gap of the new rings was exactly the same as the old rings, same with the compression before/after!

another interesting fact is that the more oil you add to your fuel the lower the octane----

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Yeah? Sure? :)

BTW, I think I remember that Rich did a controlled experiment on his RM125 and found that, corrected for jetting, 16 or 18:1 made the most power. I run 18:1 in my son's KTM Pro Sr, and 32:1 in my 500 (Royal Purple and Nutec :) ).

It's not unlike debating whether smoking will shorten your lifespan.

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...except this topic has more than one answer, eh? :uh:

motometal said:

i've just gotta ask...31:1? why an odd number?

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My bad, I meant 32:1 lol