Poor mpg - GasGas EC 300 Six Days 2011
 

My bike has been having a very poor (i think) MPG.

I can only ride about 65km/40miles before hiting reserve.

I don't know what kind of jetting I have now has I've bought the bike used.

It's a 2011 GasGas EC 300 Six Days.

I ride mixed terrain at a "medium" throtle.

Does anyone know where to start looking or if this is normal?

Thank you.

Proper jetting will help but will only get you so far. The squish, distance form the piston to the head needs to be adjusted on these bikes for them to run really crisp and get decent mileage. Search for squish on this site and you will get plenty of info. I wonder if the new bikes come with a reasonable amount of squish?

Look at the RB Designs head mod in the technical writings here, to see what is involved in what PEB is speaking of.

It and jetting are the only upgrades my engine needed. It ran fine, but the difference in fuel mileage and extra low end torque make this $85 head mod the best money you can spend on the engine.
I was pissed at myself for waiting over a year to do it to my 2006 DE300. Due to more efficient fuel burn and less throttle used, my fuel use was cut in half.

That's why I did it to my 2011 EC250 as soon as I had put three hours on the bike (to make sure it didn't have any issues I might need to fix while I waited for RB to do the head mod and of course the time it took for shipping both ways.) It only took about a week, which I used to put the guards on the bike and have the suspension customized; which was another thing I kicked myself for delaying on the '06.

You might want to check your float level. Too low, and your carb can spit fuel out the overflow on hard bounces. There are tech posts that are GasGas specific on this procedure, both here and on youtube.

Is your bike running well, except for poor mileage?
When you learn your jetting, you can compare it to what others are using.
I run a N3CJ needle with the clip in the second groove from the top (2009 Yamaha YZ250 jet needle) There are other's that will work just fine. It depends on what power delivery you prefer.
175 Main
42 pilot (slow) jet
#7 slide
I do most of my riding under 1k', seldom get over 3k' in elevation.

It happened to me recently.

Turned out my float level magically changed.

Too much fuel in the bowl.

Now I'm getting around 90km with a full tank.

Finally could see the jetting I have as I had stripped bolts on the way.

stock needle
172 Main
38 pilot

Its the 38mm carb.

I don't know what is the "#7 slide" you're talking about. Could you explain?

Also, I have a spare NECW needle as everyone says its better for the Gassers.

Thank you.

The slide number is stamped onto the slide.
It designates the height of the "cutout" at the bottom of the slide, which determines how much air passes under the slide at low throttle positions.

If I replace the stock needle with a suzuki one (NECW) would I need to change anything else?

Just your fine tuning adjustments. (possibly the needle clip groove, the air screw, and idle screw)