Messages

1

Technical / Re: What two stroke pre mix is best?

« on: December 15, 2009, 06:54:50 PM »

I fully agree modern synthetics have a lot of plusses...however with ANY "performance" two stroke oil price is not one of them!

You would surprise yourself trying the cheapest outboard boat oil you can find that's certified TC -w3 or whatever that is...

Walmart supertech is less than 10 a gallon, and will blow your mind in performance when mixed at appropriate ratios (around 30:1 for most people works great)

Penzoil's oil is great too...along with a lot of other "budget" outboard oils.

As far as mx specific oils, pretty much can't go wrong if you mix at the right ratio for your application, some of the amsoil products burn incredibly clean though I have had some odd issues with it in other areas.
Castor 927 is IMHO the best all out race lubricant but I suggest frequent tear downs with it for carbon.

2

Technical / Re: Oil ratios verses air temp

« on: December 15, 2009, 06:50:21 PM »

Sorry, I will try to put it more clearly!
It has been conclusive in every instance of testing that a two stroke will make more power with more oil all the way to point of ignition failure!
That's in the 12:1 range.

However the improvement drops off dramatically at "some point" usually around 24:1 for most big bikes and 20:1 for most "minis"

The GP bikes are water cooled, and actually dont turn RPM's all that incredible...peak power usually around 13k.

The truly incredible engine are the kt100 class shifter karts turning upwards of 20k.

Skidding is for real...just not for most "mere" mortals, as not many truly high tech oils are for sale...I have not personally seen skidding with ANY oil even at 20:1.


Of course oil ratios depend on use and the jetting, a trail rider who puts a bike designed to scream will not need high oil ratios, where road racers, karters, and most fast mini and schoolboy kids will need more oil, as the engine stays high RPM all the time and doesn't allow oil to accumulate in the cases near as much as a trail rider's bike....

Despite the modern advances in lubrication, I have not seen ANY synthetic compare anywhere close to the performance of a castor oil under extreme duress.  castor oils have an interesting molecular structer that actually turns into a better and better lubricating oil the hotter it gets.  So much so it eventually sludges at extreme temps (it's pitfall...it requires frequent rebuilds do to carbon build up in power valves and exhaust ports...sometimes ring lands.)  All other oils, syn or not, reach a temp at which it's bonds dissapear and it fails as a lubricant, not true of castors (the opposite)

Anyways, not trying to step on toes...just the knowledge I have gained from too many engine failures and many long phone calls.

3

Technical / Re: Oil ratios verses air temp

« on: December 14, 2009, 11:18:34 PM »

Some really simple basics:

When you mix more oil, aka going from 40:1 to 32:1, you actually will lean out the engine.
This is because you now have MORE oil than you did taking up part of the mix running through you jets...and less fuel.

A change from 40:1 to 32:1 is minor, but larger changes would become more critical.

different terms are used regarding altitude, pressure, humidity as one sum, some call it RAD or relative air density, some call it density altitude etc...

They all are a means to correlate all the factors necessary to jet your engine....
Basic rule, the hotter it is outside, the leaner you go, the colder it is the richer.

More humid: Go leaner (less air getting in replaced by some amount of moisture)

Higher altitude go leaner reverse for lower.


Regarding oil ratios, while it's been argued and argued, you will find that the fastest engines often run at really high oil ratios, and the correlation has ALWAYS been more oil, more power, and more lubrication and longer life.

It's not uncommen on highly stressed engines to have oil ratios at 20:1 or even greater.

I am told the absolute highest level two strokes (moto GP 125s) are mixed at 24-32:1 using extremely high tech synthetics.  These engines have I think 2 hour life expentancy (at most) and it was found that with the new cool synthetics being so slick, the roller bearings would skid and not roll when there was too much oil...

With the oils most people run, the skidding issue is not an issue. 
There have been tests showing more oil more power, but NEVER a test showing less oil more power....
Run whatever floats your boat and budget, but I highly suggest more oil than less oil