EC 300 2012 - jetting for singletrack (not racing)

[Jakobi]

FWW the N8RK is a full clip position richer than N3CK. K is one step leaner on the straight section than J. But.. As you've stated the KTM uses a smaller carb which pulls more fuel due to increased vacuum. But.. They are also very different engines from crank case volume, to porting, to exhaust flow so any comparison on paper is just that. Its the same with jetting your bike. I can tell you what works in mine, but it might not work in yours. Depending on where we are in the world our fuels throw some pretty big variance into the picture, along with the other normal variables. I also haven't touched a 2012 model so don't know what they are asking for in terms of fuelling/carby.

What I did though, is give you a baseline that has worked for many others in the past and a battle plan on how to get things happening. Its a methodical process. To complicate things though these bikes are hard to get the pilot circuit dialled in with the air screw making a difference. A quick search on that and your mind will boggle. Basically, they run a large squish clearance from the factory to accomodate all the countries they ship to so best bet is to tune the off idle response by feel. If you go too far the idle will hang and the bike will hesitate when cracking the throttle quickly.

 

[Jakobi]

Sorry if I sounded a little rude in that last post. Been a long day here. I thought you were going from 42 N3CW#2 175 to 38 N3CJ#3 170 which is essentially 3 changes at once, and about 3 steps leaner on the idle circuit due to the change of pilot and the straight section of the needle. The real key here is to start rich, and ride the bike. Make a single change, and ride the bike. Adjust the air screw one way and ride, adjust it back the other and ride. Start to get a feel for what the different changes do and once you get it right move on to the next circuit. Its slow and painful, but it will ensure you get your bike jetted to suit your fuelling requirements.

As a baseline, I my 2010 EC300 at 25-35C, 300M-1000M, RH60%-100% uses 42 N3CJ#2 172. I could go a half clip leaner on the needle, but I know a full clip leaner is too lean, so I stay on the safe side. The 2012 engine may be a little different internally which could throw all this out the window so best start safe and rich and then lean it off by feel, step by step.

 

[pHreaC]

I have ordered a 172 and 170 main, got the 42,40 and 38PJ and the N1EF, N3EW/N3CW (which are basically the same) and N3CJ needle.
Will probably have the bike on a dynojet bench this or next week and we'll see where will end up...

thx for the advice and tips...but I reckon I will have to do some testing for my own

grtz

pHreaC

 

[Jakobi]

Definately Its the testing where you'll truly find out what works and what doesn't. The key is to do it in a way where you can understand what each change has done on its own. Some people even like to log it in a book as a record.

Look forward to hearing any results you find from the Dyno session. Having the N3EW and N3CW is a good choice as it gives you a half clip adjustment to allow you to really dial in and fine tune the clip position. Depending on how much you're looking at spending on a Dyno, you might be better off investing it in correcting the squish. It definately makes the bikes much easier to jet, and once jetted correctly much more stable to changes in alt and temp. The bonus is increased power across the rev range, and better fuel economy too.

Keep us posted!

Cheers Jake