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What 2 Stroke Fuel Ratios Should You Use For Your Go-Kart?

A good fuel mix is crucial to look after the expensive, invaluable engine and could also provide you with an edge against other drivers who were a bit more clueless. With many years’ experience at my back, and I’ll share the wisdom about fuel I’ve picked up for you!

You should usually use a fuel ratio of 8oz oil to 1 gallon of fuel for a 2-stroke go-kart. If you open the manual about your 2-stroke, there will always be a recommended fuel to oil ratio that is considered the best for efficiency, safety and overall, keeping the engine properly lubricated.

With all of that said and done, let’s look at some of the most common fuel-to-oil ratios that can be found for different engines, plus some useful tips about the whole process…

The Comer C51

This highly popular little engine that could is seen almost everywhere in kid karting, and even in higher age categories with a few tune-ups here and there. Due to how widely available this engine is, I felt that this was the best place to start due to its popularity as one of the most common 50cc engines on the market.

There are two distinct ratios that people use when topping up their C51.

The most common mixture consists of 8oz. oil to one gallon of fuel, which makes the mixture 16-parts fuel to 1-part oil resulting in a 16:1 mix. Another commonly seen mixture is 6oz. oil to one gallon of fuel, making a 21:1 ratio. The latter mixture will save you some money while properly lubricating the engine, while the former is a lot more oil-focused to truly look after the Comer.

A variation on the 16:1 is something commonly used for races, and that occurs when increasing the oil amount to 9oz. to one gallon of fuel. It combines good lubrication with a slightly less fuel amount to allow the engine better combustion, and therefore higher speeds/ more competitive racing overall.

The one thing to watch for when doing this is carbon build-up, so you’ll want to fully drain your engine after every race when looking for higher performance.

The IAME X30

Another fan favorite, this TaG-ready engine produces competitive horsepower and speeds within the 125cc race categories. This engine is typically seen in high-skill Junior divisions, all the way up to Senior classes and is celebrated for its versatility, high performance and reliability.

The manual for the X30 outlines the recommendation of fuel mixing to align with a 25:1 ratio, specifically stating that a 95-octane gasoline is best.

Much like most engine manuals, different oil types are weighed up dependent on their effectiveness with the ratio, and the best types for an IAME engine are Castor Oils. Although this type of oil makes a gummy residue of carbon deposits, it’s the best for providing competitive lubrication even at high temperatures.

The recommended oil brands are Shell Advance Racing M, Elf HTX 909 and ERG K Kart Formula.

The Vortex RoK GP

Yet another 125cc engine, the latest RoK engine of the bunch is favored in TaG racing for its varied innovations in coolant systems in order to keep it running for longer.

2-stroke engines work hard to deliver high power and torque for races, and the RoK does well to deliver on that raw power while also ensuring you won’t be shopping for replacement parts after every race.

Much like the IAME and quite a few other 125cc variants of engine, the manual for the RoK GP recommends a 4% fuel mix, which lines up as a 25:1 ratio. Unlike other manuals, Vortex don’t offer the best types of fuel and oil to mix together, and this indicates that the standard sorts work as intended.

Owners of the GP engine recommend a 100-octane gasoline for races, but for the purposes of being cost-friendly, 94-octane fuel from a pump is acceptable for practice. Mix these together with Castor Oil at the 4% mix ratio and the engine will be running at its absolute best.

The Rotax Max Engine

Above all else, Rotax is passionate about performance in racing, which is why some of their prices can be considered a little above what go-karting enthusiasts can comfortably pay.

However, their Max 125cc engine really is something special! For high-performance engines, a great mixture of fuel to oil is required, and contrary to most other types of 125cc variants, Rotax recommend something a little different…

Unlike the IAME and RoK engines mentioned previously, the makers of the Rotax Max recommend fully-synthetic kart racing oil as opposed to Caster Oil.

This is primarily because Rotax make all of their products specifically to work alongside one another, so they created a kart racing oil to specifically complement its most competitive engine.

Also, unlike other 125cc engines, there are two distinctly different fuel mixes to be used.

For the purposes of ‘breaking in’ the engine, Rotax recommend that a ratio of 30:1 should be used, putting the oil at a 3% mix. Simply put, this is the best for running the kart under normal circumstances such as while you’re practicing. And for optimum performance, such as when you roll out your Rotax for races, they recommend a 50:1 ratio which puts the oil at a 2% mix.

How To Mix 2-Stroke Fuel For A Go-Kart

Now you know the ratios required for a cross-section of different engines, probably the next most important thing is to know exactly how to create the mixtures. After all, the fuel and oil need to be mixed properly and completely!

Otherwise the oil might not properly coat the engine components, or there won’t be enough fuel for the engine to use for combustion. Follow the steps below for perfect, well-mixed results:

  1. Pour the correct amount of 2-stroke oil into a clean gas can
  2. Add the correct amount of gasoline
  3. Stir or shake the container to mix the oil and gas together
  4. Use the mixture within 30 days of mixing. After this time, the oil and gas will start separating and will cause engine damage if you add to your rig

Sounds simple enough, right? It really is an easy process when you have your mixtures down pat. Before we get down to calculating/ reading the fuel mix amounts, always remember the following tips:

  • Don’t use automobile motor oil! It contains noncombustible additives which will damage your engine/ make it impossible for combustion to occur. Only use 2-stroke/ 2-cycle engine oil
  • Never use gasoline with more than 10% ethanol! This is because ethanol attracts moisture, which causes gasoline to break down and will cause engine damage
  • Don’t ever eyeball your gas and oil amounts; make sure to properly measure everything according to your ratio
  • Don’t mix gas and oil in the engine itself! Always use a separate, clean container to do the job
  • If you’re taking your kart out of winter storage, allow the engine to fully drain first before adding a new mixture

How To Read Ratio Charts

Alright, now it’s time for some Math! Exciting, right? Not for me, let me tell you that much. It never was my strong suit but it’s really crucial for getting your fuel mixes right and having a general know-how about the different charts you’ll see/ how to work things out for yourself.

Most ratio charts will actually come with two different units of measurement listed; milliliters per liter and ounces per gallon. Because of this, you don’t have to do the tricky conversions between liters and gallons or vice versa. If all else fails, remember that 1 liter is equal to approximately 0.26 of a gallon.

When figuring out the amounts of gasoline and oil to fit your listed ratio, you first need to look at how much gasoline you have. For example, let’s say that you want to mix your fuel to the Rotax recommended base-line of 30:1 and you have 2 gallons of gasoline. How much oil should you add for your fuel mix to be correct?

You take your fuel amount which is 2 gallons, convert to ounces which is 256, and then divide that latter amount by the ratio you want which in this case would be 30. 256 divided by 30 would equal 8.5oz., so you would mix that amount of oil in with your gasoline. Then, voila! The perfect 30:1 fuel mixture for practice sessions in your Rotax.

Most charts will make it very clear for you, but it’s always nice to have the formulas you need to work things out by yourself in the workshop when you don’t have one to hand. Nevertheless, you can find multiple different fuel mix charts online and print one off so you have it handy.

Final Thoughts

Above anything else, you should always be looking for the manufacturer recommended fuel mix ratios. There are variations to be had, of course; especially between practice and race conditions.

Remember that a little too much oil is always better than not enough, and find which amounts will work best for your rig. You’ll be a fuel mixing pro in no time!