High Octance Gas Conundrum

I sell a lot of the China import scooters/mopeds with a 49.5cc engine. The owners manuals claim that 90 octane gasoline is the minimum requirement. They all have the Honda GY6 clone engines with no timing adjustment. I started experimenting with fuel types/octane ratings and found the following to be true.

All of the brands we sell say not to use ethanol enhanced fuels. 87 octane fuel runs terrible; 92-93 octane fuel makes them run worse than that! 89 octane fuel with "no ethanol" seems to be the happy medium. 90 octane leaded fuel works the very best. It's available at most farm cooperatives here in the midwest. It's red in color; and actually smells like gasoline.

A product called "Marvel's Mystery Oil" can be used as an additive to any gasoline to provide excellent upper cylinder lubrication.

Brett

One thing to remember about recommended octane levels coming from other countries is that they have different rating systems. Japan and Europe use a system called RON or Research Octane Number to determine the octane rating of their gasoline, while stateside we use a system called AKI or Anti-Knock Index to determine gasoline's octane rating... Interestingly, to further complicate things it would seem that our own AKI system is actually derived from the average of the RON system and another more complicated system referred to as MON or Motor Octane Number... So, to recap our methodologies for measuring gasoline's octane rating are different, but share some common elements...
So, with the commonality of RON in mind a good rule of thumb is as follows, multiply the foreign RON Octane rating by 0.95 and you will have the US AKI equivalent.

( RON Octane Rating x 0.95 = AKI Octane Rating )
90 RON Octane x 0.95 = 85.5 AKI Octane (US measure)
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

So, as you can see the 93 or 94 octane fuel we are all paying an arm and a leg for is actually quite comparable to the higher octane fuels found in Europe and Japan. I suspect that the recommended 90 Octane rating that you are getting from the Chinese motors is based off of the RON Octane rating and would equate to AKI (or US method) Octane rating of only 85.5


Warner



PS - What compression ratio do those Chinese engines run at?
 
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SO....what is the bottom line? These HT engines that most of us run (2 strokes)...are they a low or high compression engine? And ideally, based on that, should I be running 87 or 93?

Which is it? Aghhh!
 
Our Happy Times are relatively low compression and you should you use the lowest octane gas you can.
 
Coincidentally if the fuel you buy has red it's dye, and meant for off-road use because there hasn't been road tax paid on it.

I wonder how the green dye of most 2-stroke oil would affect it.

Legally, you CAN use road-taxed leaded fuel if you can find it, as our HT motors have no "unleaded fuel only" disclaimer. Even my lawnmower has that!

OT, but I got a couple gallons of "white gas", aka coleman fuel, on post-winter closeout for $1/gal. I used it all up in my mower last summer. It worked great! It's a real low octane unleaded fuel... low b/c of it has no additives at all for boosting octane so it burns clean in camp stoves or whatever. My briggs mower calls for, IIRC, 77 octane, LOL.
 
HT's are low compression engines. (6.0:1 to 7.5:1) The "plastic fantastics" a.k.a. china scooters/mopeds are relatively high compression. (9.0:1 to 10.5:1) The "Happy Times" bikes should run fine on any low grade fuel. The China scooters run best on 89-90 octane leaded fuel.

Brett
 
Coincidentally if the fuel you buy has red it's dye, and meant for off-road use because there hasn't been road tax paid on it.

I wonder how the green dye of most 2-stroke oil would affect it.

Legally, you CAN use road-taxed leaded fuel if you can find it, as our HT motors have no "unleaded fuel only" disclaimer. Even my lawnmower has that!

OT, but I got a couple gallons of "white gas", aka coleman fuel, on post-winter closeout for $1/gal. I used it all up in my mower last summer. It worked great! It's a real low octane unleaded fuel... low b/c of it has no additives at all for boosting octane so it burns clean in camp stoves or whatever. My briggs mower calls for, IIRC, 77 octane, LOL.

Has anyone tryed using this coleman fuel on happy time engines. Was there any pinking when you ran it on your lawnmower. I'm thinking this coleman fuel is tax free thus cheaper.

BSA
 
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