FAQ: Premix Calculations

[MattR]

Question:
The GasGas manual specifies a premix ratio of 50:1 (or 2% oil). How do you determine the required amount of oil for different quantities of gas?

Answer:
The manual does specify 50:1. However, many riders have found other ratios such as 40:1 and 36:1 to work well in GasGas bikes. Personally, I like to use 40:1 in my bike. There are products on the market such as "Ratio Rite" which help riders determine the amount of oil per gallon of gas.

A better method for determining the oil for any quantity of gas is to develop your own premix table. Your premix table will allow you to determine oil for smaller quantities of fuel (such as emergencies on longer rides) or mix up larger quantities of fuel before a ride.

Here are premix tables that I have created for reference. I created tables for the most common premix ratios. You can print out these tables for your fanny pack or garage use.

 

[flybars]

Premix Calculations

Sweet! Takes all the guesswork out of it. Eliminates mistakes.

 

[tprnottp]

Matt,

You be da man!

Thanks for doing the leg work for the rest of us.

TP
'03 EC 300

 

[MattR]

Thanks! Glad you liked them.

 

[Hawkeye]

My brother did a similar chart many years ago, but he just picked his ratio and then listed the oz. needed to mix with gas in tenths of a gallon. He formatted it out to look like a rollchart and then taped it to his front fender or his gas tank. When we trailrode, like the Six Days of Michigan, it worked great to get the proper ratio in your tank after topping it off at the gas pump.

 

[MattR]

Here is a table for 43:1 premix ratio:
As you can see, this makes it easy with 3 oz. per gallon.

 

[Brian VT]

I like the 3 oz. per gallon rate.
I pack an 8 1/2 oz. Listerine bottle of oil. It's flat and sturdy. I pour in oil and make marks for every 1 1/2 oz.
I've never used all 8 oz. but there always seems to be someone who forgot to pack oil.

 

[lankydoug]

If you're home and or have access to the internet here is a link that is useful. If I top off my fuel storage can before a trip I can enter the decimal amount and get the exact calculation as well

http://www.qddev.com/demos/sprockets/sprocketpremix.shtml

 

[GasGas]

Man I'm glad we went metric back in the 70's. All this stuff is so much easier to figure out in litres versus gal. When working in litres just convert to ml ( litres * 1000) and divide by your mix ratio. So for mix ratio of 36:1 for 20 litres of fuel just divide 20000 by 36 = 555 ml

 

[steliost]

Hi all, I thought this would be the right place to post this. What do you think about 1.7-1.8 % oil ratio? The local gasgas dealer and mechanic, very experienced on riding, racing and maintaining 2 strokes mostly GG and Husaberg, swears by using 1.5% or 66:1 (!!!) on his bikes, even on his 125 2012 husaberg. His claims: less spooge, better performance without risking to seize the piston and bearings. Also he insists on Agip premix oil. What is your opinion on the subject?

 

[Jakobi]

The bottom end bearings will run submerged in oil. They won't run very long dry. In saying that some people run with next to no oil. Some use heaps. Whats more important is using a quality oil and jetting to suit the ratio you use.

FWW most oil manufacturers will specify a ratio.

From http://www.opieoils.co.uk/p-926-mot...lubricant-of-mx-250cc-world-championship.aspx
About Motul 800 2T Factory Line OFF ROAD Lubricant of MX 250cc World Championship

Lubricant of MX 250cc World Championship
Premix Racing 2 stroke Engines
100% Synthetic - Ester

Formula developed for Motocross Grand Prix Teams. Suitable with standard and unleaded gasoline up to 124 octane
All racing 2 stroke engines, high performance and using premix : Moto cross, Enduro, Trials, Quads, Watercrafts, Ultra lights...
For road bikes, use MOTUL 800 2T ROAD RACING. For oil injector systems, use MOTUL 710 2T.

RECOMMENDATIONS
Mixing ratio : MOTO CROSS GRAND PRIX : 2% (50:1). In normal conditions decrease the percentage by 0.5%.
Tune according to your own use.

So there you have 1.5% mix as stated by the manufacturer. 66:1 under normal conditions.

 

[Rick]

Jokobi,

I was using Motul 800 for years, but the drip from my s/a was pissing me off, getting all over the fender, jersey and dripping down onto the singarm.

I have been running the same jetting for about 10 years now. I recently switched from the 800 to the 710 at 40/1. Once I switched, no more oil drip, no more blowing out on the rear fender. It feels like the bike runs "cleaner". The crazy thing is the plug looks the same?

What is your opnion of this?

Is it "ok" to run a injector oil?

Thanks

 

[Jakobi]

I dont use it either. But my question is. Were you running it at 66:1 like they suggest you should for trail work? Or 40:1? I imagine that would make a big difference to spooge factor. The 800 is noticably thicker and has a higher flash point too. Never going to burn as clean unless if you're working the bike hard.

I use GRO/Amsoil Dominator, both at 50:1 and have always had an oily ring at the tip of the pipe. Stock jetting was the only time I ever had excessive smoke and spooge.

 

[Rick]

To answer your question...no I never ran it at 66/1. I should give it a try.

Thanks

 

[Jakobi]

I wouldn't even bother really unless if you wanted to. Your bike is jetted for 40:1 and runs well and clean on the 710. I'd say keep with what you know is working for you. Its still a good oil and you're putting more into the engine.

 

[Rick]

Thanks for the info.

 

[Jon250]

Hi
I work it out 11 litres of fuel so 11000 divided 50 for 50:1 gives 220 ml of oil just change the 50 to the ratio you use.

 

[GASGASCWB]

Hi
I work it out 11 litres of fuel so 11000 divided 50 for 50:1 gives 220 ml of oil just change the 50 to the ratio you use.

I use MOTOREX CROSS POWER 100/1 (1%) on my last 2 stroke bikes and have no problem!

In past I use MOTUL 800, but the smoke and grease on the exhaust is enormous...

I have a friends that use MOTOREX CROSS POWER 0.6%, 0,8% and the engine is perfect.

 

[Jacob 'Berg]

I use MOTOREX CROSS POWER 100/1 (1%) on my last 2 stroke bikes and have no problem!

In past I use MOTUL 800, but the smoke and grease on the exhaust is enormous...

I have a friends that use MOTOREX CROSS POWER 0.6%, 0,8% and the engine is perfect.

And I get nervous running 50:1 (2%)!

 

[GASGASCWB]

And I get nervous running 50:1 (2%)!

with CROSS POWER USE 1% and do not worry! we used it in Brazil where the weather is very hot for most of the year and our gasoline is worst in planet: at least 27.5% ethanol and some unidentified chemistry products...

Go ahead with MOTOREX CROSS POWER 1% and Braaaaaaaaaap...