1987 CR250 oil Ratio

[Hoony]

Do the “Modern” castor based oils like 927 cause the issues we used to get with “Shell M” (Mixed with Shell A - fuel).
Like “Jelly” in the carb if allowed to stand. More “gumming” in the engine. (No power-valves in the old days)

this is the methanol doing the “Jelly” in the carb. i had a speedway bike (4T) for years, if i didn't drain the carb after the meeting this was the result.

[sleepy]

927 burns cleanly in NY opinion. Ithink they have cleaned it up. The contemporary Castrol R seems cleaner as well

The current castor based oils are much cleaner due to the additives mixed with the base castor oil. Every 2 stroke oil sold today has detergents added to help keep things clean even the Full synthetics. One thing to be careful of when deciding on a mix ratio is to not go outside the oil manufactures recommendations. It gets complicated but if you use an oil made to mix from 50:1 to 100:1 at 25:1 the concentration of detergent and other additives in the final mix may be to high to work and can even have the opposite affect causing very high carbon build up.
Other thing to think about with Ester based oils is that the oil is Hygroscopic and can cause internal corrosion so there is normally an additive to help stop corrosion. This was never a problem back in the old days of mineral oil. I've pulled apart motors that haven't been run since 1970 and the bearings once cleaned are as good as new but not case with the modern oils.   

[Ted]

We run a 73 YZ 125, 73 YZ 250, 77 RM 125, 81 YZ 465, 94 KX 500 all on Maxima 927 castor oil at 30:1. These bikes have never lost a race at Nats, Origin or Conondale Classic level. They are ridden flat out for the entire  3-4-5 laps every race by the two fastest guys in VMX with no issues.
So for anybody advocating 40,50,60,1000:1, keep it up. Just makes our job a lot easier??

[Barra]

Funny how nothing has been mentioned about the heat retention characteristics of the various oils.

I was told by an esteemed world class tuner (this is 15 y.o. info) that synthetic oils hold far more heat than mineral oils. The logic being that synthetics are 'plastic' and we all know how hot plastics can get.  The result is more cooked big / little ends.   Mineral oils hold less heat and so 'wash out' the heat more.

Anyone ever heard this theory?

Also, go-kart guys will tell you how small high revving 2 bangers gain better ring seal and more horsepower from a rich oil mix e.g. 16:1     

[Nebo]

 I agree with Ted. ( Not often ).   That Maxima 927 is a very good oil.
  But some of you are getting off the point of oil/fuel Ratios.
KX80/85,Go karts, and Road Racing Engines are really a different subject as the Engines are operated at much higher RPMs at long periods of time at full throttle.

A friend worked at a Kawasaki Dealer . He would rebuild KX80/85 Cranks some times 5 or 6 a week for the Junior A Grade Riders.
He stated that using  Castrol A747 or Kawasaki Racing 2 Stroke made the Cranks last longer.

Honda HRC Australia used a Special Shell oil made in Japan to run in the NSR 250. It came in a screw top metal container and the writing was in Japanese. So i know little about it and if it was Mineral or Synthetic. It gave good Piston and Crankshaft life . It was never Sold Retail even in Japan.   It was mixed 30.1.
Would not use  Shell VX/VX2 2 stroke oil .  Found to not burn clean and has a lot of smoke.

Castrol A747 has been used  Road racing bikes for many years and still is.  But it is expensive but so are engine Rebuilds.

 When Belray MC-1 first came market it made may claims including low smoke,less plug folling and clean burning etc.
 Clean burning was true . If run at 40/50-1 it burnt that clean not much oil was left when it got down to the big end.
It was recommended by our Maico Dealer and Maico USA to run MC-1 at 25-1.  Used it for some time with no problems.
Then switched to Castrol TTS and used it for many years.

Someone brought up Bearing Skid. Have not heard this term for many years. I know it will happen if you use Moly grease on Taper Car Wheel bearings but as far as engines go i have not heard of it since i read a article from Alpha bearings UK.

The paper was written in the early 1950,s. They built a much improved crank and rod for the Villers engine with a bigger
pin and Caged rollers.  Which helped with Bearing Skid and Clearance problems.

Just note the first thing a rider does when a Engine fails is blame the oil. It is has and can be caused by something 
 like Dirt/Dust , Dirty water, Air leaks, Spark Timing / Detonation etc. Or just worn out.

Another Point to think about is the oil ratio effects Combustion Temperature, Carburetor Jet flow and Changes the
 Fuel Octane Level.