Just bought a 1983 Yz 490 also have a 1985 Yz 250 I run the 250 at 32:1 mix using hp2 2 stroke oil kid I bought the 490 from says he used a 50:1 mix what do you guys suggest? Should I run 32:1 in the 490 also? Thanx for your time
I am still on 20-1 mixes. A big one that is actually held wide open ends up blowing it out really fast due to volume. if you are like most people you will enjoy not having to shift down very much and will delight yourself by rolling on the throttle in 3 gear around corners at walking speed and rolling the throttle on and repeating just to show you can. In other words, lugging to the extreme. Life can be tough on a big two stroke. So I still use 20-1 mixes. Especially on my big ones, because I know I am going to lug them, and I know when I get on a long stretch of straight stuff it will be wound up to where the pipe and carburetor work to keep it from reving any further.
uhuh. I cant remember what the yz manual called for. my 87 cr500 came with 20-1 on the fender, but I had been using that since the 60's anyway.
My XC calls for 60:1, but I don't go less than 50:1. The jap bikes will get whatever I put in the kaboom.
I'm cringing.
The WR500 has seen neary 400 hours with a 32:1 walmart marine oil mix. Not one deposit or abnormal wear marks. I completely lug it some rides, and other rides I hold her to the stop.
Check out my build threads to see the internals yourself. Hundreds of photos.
Honestly if you do the actual math, changing from 20:1 to 40:1 (2.5%) is less than one jet change (3.8%)in the carburetor. So ultimately the oil/fuel mixture conversation is totally dead in my mind. Air/fuel mix on the other hand...
-BIG DAN![]()
I was surprised also, but the manual stated run in at 40-1 then continue with 60:1. When I pulled mine down for the first time this year after 3 seasons, I saw zero sign of oil starvation. I wonder if case reeds allow for the same lubrication with a leaner mixture as cylinder induction with a richer mix....no idea just a thought.
The WR500 has seen neary 400 hours with a 32:1 walmart marine oil mix. Not one deposit or abnormal wear marks. I completely lug it some rides, and other rides I hold her to the stop.
Check out my build threads to see the internals yourself. Hundreds of photos.
Honestly if you do the actual math, changing from 20:1 to 40:1 (2.5%) is less than one jet change (3.8%)in the carburetor. So ultimately the oil/fuel mixture conversation is totally dead in my mind. Air/fuel mix on the other hand...
-BIG DAN![]()