Hi,

So I am having some issues with choosing main jet. I've read the rejetting matrix, searched, and hand wrenched a LOT already.

I have a '96 motored GS that I have risen from the dead. I just swapped in '05 carbs with KN lunchbox, stock exhuast.
Test#1:
I tried rejetting matrix, 20 / 65 / 142.5, with adjustable needles 4th position from the top (it came with the carbs off ebay), white thick washer and thin metal washer (#4?)
Results#1: 
Bike was sluggish 1/4 throttle - 1/2 throttle. Full Throttle resulted in popping&hesitation from engine/carbs from ~5k - 8k, above 8k mediocre.

Thought popping was lean condition so I covered the top of the lunch box with duct tape, no change, slightly worse.

Test #2
Same jets, changed adjustable needle to 2nd position from top with white thick washer and thin metal washer.
Result #2:
1/4 - 1/2 throttle much stronger pull, full throttle still popping&hesitation from ~5k - 8k, above 8k mediocre

Again tested with duct tape coving top of lunch box... no change.

Test#3
Change main jet to 124 (came with carbs from ebay), same pilot and mid as above. needle position 2nd from top with thick washer and metal thin.
Result #3
1/4 throttle terrible & stuttering, 1/2 throttle mediocre, full throttle much stronger pull above 8k, no popping....

Engine is old, and may need a valve adjustment, I'm not sure if it would even help... but I believe the 142.5 main is too large and is causing the popping... but how do you decide how much smaller? Do I just buy a bunch of jets and try each one?

Thanks for your help.

Valve adjust is a must to get carbs tuned properly.The carbs will also need to be balanced or sync'd,same thing.Have you adjusted the air fuel enrichment screws?They are under two round brass plugs, if they haven't been removed.Your first jetting specs sounds correct for a free flowing exhaust and lunch box.Don't block off airflow through the air filter.It will cause more issues.What is your location, or better yet,what altitude are you riding at?

I'll check valve next weekend.... as for carb sync.. they're from an '05 which isn't really that old and shouldn't be far off sync. I'll have to check this too....
The air screws are 3 turns out, in line with rejetting matrix. I'm in Los Angeles, so I'm near sea level...

K&N lunchbox with stock pipe - several people have tried it and found it near impossible to jet right. I'd however guess that with the stock needles it is closer to 142.5. With DJ needles it is closer to 130.
Close vs perfect is a looooooooooooooooong way IMHO.
Carburetion needs to be perfect, because it can be.
Cool.
Buddha.

Update:

Bought 130 and 135 jets.
First tried the 135, so I'm at 20/65/135, 3 turns air screw, needle at 2nd from top.
Bogging off the line to about 2.5K rpm, above 2.5k 1/4 , 1/2 and full throttle are better now, but don't feel optimal.

Then tried 4 turns on air screw,
Similar results as above

Tried closing air screw (0 turns)
Bogging stopped, but feels underpowered in low range

Tried 1 turn , then 2 turns.
Off the line is better, 1/4 and 1/2 throttle are good, full throttle is good

Tried to move needle clip down 1 position (3rd from top) to enrich the full mixture. Still runs good on flat roads.

Bike runs good, but felt that with 142.5 main's had better 1/4 and 1/2 throttle.
Had a ride to work today, I have  to climb a tall hill, and the bike seemed to be popping at about 3/4 to full throttle... might need to raise needle position and try again.

Odd thing now is that the bike is difficult to warm up, opening choke all the way doesn't raise the RPM. Without warm up the bike is still ride able and little hesitation at 1/4 throttle.

I feel that I need a 137.5+ main to get this sucker working right, though I can't be sure without more testing.. or if I had an o2 sensor

Update

Went to 22.5 / 65 / 137.5, 3.5 turns out, 2nd needle position

Bike feels better, but <3k rpm is still hesitating a little bit. Bike will raise revs and warm up now...

Has anyone used 25 pilots with any success? It kinda seems to me that i have a vacuum leak, but then I would expect the whole RPM range to be screwed.

Pilots control the bike's carburetion as you take off from a stop. Like a normal stop, not a rev to the moon and take off tires spinning take off.
Cool.
Buddha.

Quote from: franke3c on June 22, 2011, 11:38:07 PM
Update

Went to 22.5 / 65 / 137.5, 3.5 turns out, 2nd needle position

Bike feels better, but <3k rpm is still hesitating a little bit. Bike will raise revs and warm up now...

Has anyone used 25 pilots with any success? It kinda seems to me that i have a vacuum leak, but then I would expect the whole RPM range to be screwed.

If you have the needles with 4 clip positions,then raise the needle one more notch.You don't even have to pull the carbs to make the change.

Here is the tuning procedure for our style carbs.

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html