View Single Post
Old 04-15-2013, 07:15 AM   #60
Sporting Wood OP
I <3 Energizer Bunny
Sporting Wood's Avatar
Joined: Oct 2011
Location: Horneytown, NC
Oddometer: 896
Originally Posted by mousitsas View Post
I am lost in jetting space!

Lets find a baseline which works well starting from STOCK (I am not shouting!) settings so we carb beginners will not get confused with all those terms.

As I understand, going from stock to ITG, we need to change:

1) floats from 3mm to 4mm (is that leaner?)
2) Lift needles from 2nd to 3rd
3) Up mains to whatever (170 to 180), depending on elevation and exhaust.

Are the FP needles a must?
FP needles are not a must...though I really like them.

I would first determine what sort of riding I'm planning on doing and where, how high. Different sorts of riding call for different sorts of jetting. I'm touring and crossing all levels of elevation so I have a rather conservative setup that's somewhat lean at sea level but can work very high up too, though it begins to get a tad rich. It returns excellent mileage and also provides lots of hp.

Within a specific elevation range, one may better setup for either power or economy. I've had mine setup with the 45 pilots and it had far more willingness to loft the front wheel. Mileage wasn't as good and when I climbed up into the mountains, it would bog down far too rich.

Fwiw, the most important thing I have gleaned from messing with these carbs is that the float needs to be set leaner than the factories 3mm. This is an absolute critical adjustment, and a rather fiddly one to get correct. The float height baselines the entire carb. I set it to 4mm regardless of what sort of jetting setup I'm after.

The next consideration is which pilot jet. 42 or 45. 45= more HP at lower elevations, slightly less mpg and a bit less friendly at high elevations. 42 is weaker though more flexible.

I consider mains next. What runs out at wfo with the float and slows set. This isn't the typical order of jetting a carb such as this but I find it works. With this filter, we expect to be in a range between 172 and 182, depending on elevation and pipe.

Needle position is entirely about transitioning from the slow circuit to the mains. What works well on one bike may not on the next. If the bike feels a bit lazy spooling up through 4000 rpms, then it may benefit from a higher needle. If it bogs down when you twist the throttle at transition, it may be too high. Typically its at 2 or 3 with these bikes. Note though, that there is a fair amount of bleed through while the needle is closed and this affects the low circuit a bit. Raising the needle typically results in enriching the bottom so it sometimes is necessary to compensate with the fuel screws.

I baseline the screws at 2 turns out with 42 pilots, and 1.5 turns with 45 pilots. Fine adjust from there. Without Satan's airbox out of the way, they can be accessed with the right tank off...which makes adjustment far easier. I will turn up idle to 2000+ rpm and pull the rear plug wire...turning the bike into a thumper.. Then adjust the screw at roughly 2000 until it runs best. Count the turns out and transfer to the rear carb.

This is the way I approach it, and I'm no means a master of Keihen's domain. Jetting varies so much between riders and places that its fairly tough to nail down a prescribed setup. Endeavor to get it close...

Sporting Wood screwed with this post 04-25-2013 at 03:46 AM
Sporting Wood is offline   Reply With Quote