SuperMoto Junkie banner

1 - 5 of 5 Posts

·
Registered
Joined
·
105 Posts
Discussion Starter #1
I just did The 3x3 and removed nearly all the plastic on top. Full yosh Rs2 Exhaust and a K&N filter. I used a Dynojet jet kit with the needle and a 155 main, is this ok or should I go 160. Its more power but it doesn't seem like its as much as people say. Is there anywhere i can buy a bigger pilot jet to match? Also what is the stock sprocket size on a 05 sm is it a 14t or 15t. I plan on getting a new one with one more tooth for better highway speed.

Thanks
Tony
 

·
Registered
Joined
·
1,202 Posts
If you cut nearly the whole top off your airbox, you didn't do the 3x3. You did whatever size opening you have. Your jetting is off, because all of the information available revolves around stock airboxes, and ones w/ a 3" by 3" opening. You're going to have to tune it on your own w/ a larger opening. It makes a big difference in the jetting specs., that's why all the information says to cut it exactly 3" by 3". A stock engine has no use for any more airflow than is privided by said "3x3 mod" anyways. Tape off a 3" by 3" opening and ride it to see how it responds. Did you do the pilot circuit test to determine if you need a larger pilot jet? Bigger doesn't mean better, and the pilot circuit has nothing to do w/ the running performance of the bike.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #4
o really?? so it would be better to tape up some of it than to jet better. and honestly I have no idea what a pilot circuit test is.
 

·
Registered
Joined
·
1,202 Posts
Yes, it would be better to tape off the top of the airbox to a 3"x3" hole, if you jetted your bike using specifications for your elevation and the 3x3 mod. Bigger jets doesn't mean "jetted better". Your providing the proper fuel for the airflow in your engine via the proper jets. Too much fuel doesn't do any good. Too much air and not enough fuel doesn't do your engine any good either. That's why the folks who manufacture jet kits test the bikes on a dynometer w/ air/fuel meters to find the proper specs. They need to be w/in certain parameters for your engine to run properly.

Pilot circuit check:

"with the bike warm and idleing turn the fuel screw in till the idle drops/misses.then go back out till the idle peaks/smooths.

this should happen between 1 and 2.5 turns on a fcr carb and 1 and 3 turns on a cv.

if you end up at less than 1 turn you need a smaller pilot jet.more than 2.5 (or 3 turns on a cv) you need a bigger pilot jet.

choose the appropriate size and retest."



Determining the proper main jet:

"Starting with the recommended main, remove the airbox door and go for a ride (bike fully warmed up). Is it better or worse?
If it is better, you need a smaller main.
Go down one size, replace the airbox door, ride. Remove the airbox door and test again. Better or worse? If better, go down a size again. Keep repeating this till the test with the airbox door is worse.

If it was worse with the airbox door removed, tape over 1/3 of your 3X3, test.
If it is worse now with the tape and was worse with the airbox door off, your main is just right. You are done!

If it seems better, you need to go up a size in main jet. Test it again (remove the tape). Replace the tape, test again. If with the tape on it is better, go up another size in main. Keep repeating this till having the tape on is worse than with it off.
To finish up and ensure you are set accurately, retest the bike with the tape off, ride it, then remove the airbox door. Best performance should be with the airbox untapped, airbox door on.

Remember, the main only operates at WOT. Ideally, you want to be in 3rd of 4th gear doing the tests, hitting max revs (just shy of the limiter) for at least 10 seconds to get an accurate representation of the jet status.
 
1 - 5 of 5 Posts
Top