slow speed jetting

[BigBore]

Rode for about 50 miles yesterday. Noticed some things about my jetting. First off, the facts:

Riding at sea level to 2000ft
Usually around 70 degrees, humidity 60-70%
92 octane pump fuel
Torco GP-7 @ 40:1
I'm pretty sure the pilot is a 45, as the spare jet I got with the bike is a 48.
NOZH needle, 2nd position from top.
Air screw 1 1/4 turns out.

The only thing I've changed is the needle clip position. I leaned it out to the 2nd position, and it seemed to smooth things out a little. The bike still runs rough and sputters at slight throttle openings. I notice this most while cruising on gravel roads with the throttle barely open, and in really tight trails while in 1st gear, just crawling along. At first I assumed this was because of a too-rich pilot jet. However, yesterday while on a gravel section between trails, I noticed that if I barely held the throttle open, and the engine was sputtering, there was also a hollow knocking sound from the motor. I would also get the same noise if I quickly chopped the throttle. This would indicate a lean condition, right? It also seems strange I should have to use the 2nd clip position on the needle. The owners manual doesn't recommend a needle setting like that until you get up into higher elevations.

This is really the only problem I have with my jetting.....just sputters off idle. If I just pin the thing and stir the gearbox, it comes unwound and hauls ass. However, most of my riding is in the tight stuff, constantly on/off the throttle in small increments.

Any tips and ideas will be GREATLY appreciated.

 

[fatty_k]

Try turning your air screw out a 1/4 turn at a time. That should give you better throtle response. If it bogs and makes a booooowaaaahhh sound when you crack it open off idle, it's too lean; turn it back in a bit. If you find the best performance with the airscrew more than 2 turns out, go to the next richer pilot. Hope this helps, I am still new to the jetting game.

 

[lawman]

i think fatty misspoke a little; i think he meant to say that if your a/s is several turns out, you need the next LEANER pilot.

 

[D Lafleur]

Big Bore, have you looked at the plug? Let us know what the plug looks like, and I will check my setup. I am riding the same bike at sea level-1000ft. 70-105 degrees F. It took me several tries, but it now runs like an electric motor, smooth from idle to WOT.


See you on the trail.

 

[fatty_k]

Yup, I knew I messed it up somwhere. :o :think: