2006 ec300 top end splutter

[motopsycho87]

Hi guys, I got my bike not too long ago, it seemed to have no top end, main jet was 172 (15c and sea level) so using the guide I am currently on 185 and looking to back off to 182. Anyway, the bike rides really well, but if I spend even a short time at low rpm, next time I open the bike up to high revs, it coughs and sputters as if it's clearing out, then rides really well (if a little flat on top, hence I am backing off the main jet). I am 3 turns out on the air screw atm leading me to believe the pilot jet was too rich (haven't removed it yet to see jet size), is a rich pilot jet really enough to gam the cylinder enough at low RPM that it needs clearing out almost every time I go full throttle? The bike starts first kick almost every time and runs really well, the power valve is operating properly, and I have replaced the spark plug and ignition coil also. Bike has V-force 3 reed block (is this standard?).

 

[Jakobi]

You'll never jet out a mechanical issue so being a 7 year old bike thats your main priority. If everything checks out mechanically, then you'll want to take the time to evaluate your current configuration. Temp, elevation, carb model, current jetting specs (slide#, needle, clip position, pilot, air screw, and main). Then compare against the jetting database for similar years to get an idea of what others found to work.

Once everything else is in the ballpark you'll get much more advice on how to fine tune it down.

 

[einsteingarage]

I will have to look for the needle # but there is a yamaha yz250 mx needle (special order) that worked wonders for my 2006 300

 

[The Angry Chook]

I will have to look for the needle # but there is a yamaha yz250 mx needle (special order) that worked wonders for my 2006 300

N3EJ...
I just did the jetting on my 07 300.
From a 2000, 2001 and 2011 yz or 250 exc.
Airscrew seems a touch far out and main may be rich but get the other info and have a look.

 

[motopsycho87]

N3EJ is the holy grail of needles? What clip?

I've got to wait until the weekend to change the pilot, house sitting atm so can't work on the bike. The bike is perfectly ride-able though, it just seems as though it is gumming up with fuel, then after a blast it is ok for a short while. At 3 screws out it doesn't eventually die at idle, so I know the pilot is close. There is immense power (compared to other 2 strokes) just off idle, there seems to be a flat spot somewhere in the middle, then pulls really hard until another slight flat spot (I don't know how these bikes over rev? With nothing to compare to, I will just go down a main jet, but it doesn't smoke etc)

 

[Jakobi]

Depending on the carb model the jetting specs will vary. N3EJ works very well for those with the AS2 - Short bowl and flat metal cap. The AS1 - Deep bowl and round threaded cap, will require a richer needle unless at altitude.. reports show probably a G Diameter (N3EG), which is still an optional needle through KTM and Yamaha. Also, changing the needle diameter will change your idle mixture so expect your almost perfect pilot to not be so perfect if you make a significant change to the needle.

 

[The Angry Chook]

I did actually mean to say N3EG not j but I've been having nightmares of needles and jets recently I spent so long looking at them that they're all dissolving into one. I'm almost about to give them all names instead of numbers!

 

[estwudsracer]

When I aguired my 2010 used, it was doing the exact same thing! Smaller main jet made it better. BUT, I ended up biting the bullet and sent my head and carb to RB Designs. For $200+/- he had it back to me in a week. The difference is AMAZING! You would not believe how good it will run. It is BY FAR the best $ Ive ever spent on improving a bike. Right out of the box I bolted the parts back on, and I couldnt be happier.