Rejetted my GS for K&N Lunchbox

[LostDog]

After ordering the wrong jets the first time, I finally got my bike running again. It goes much quicker the when you've done it before. I put 147.5 mains in the first time and it hardly ran. These are the jets listed on the rejetting matrix for the K&N pods. I managed to find the right info, 140 mains, on the forums. When I was adding the lunchbox info to the matrix I decided to try out a new table format.

Updated Rejetting Matrix

Since the lunchbox seems to be a popular choice, It'd probably be cool if someone could add info for it in the 2001+ table.

[Wrecent_Wryder]

f3

[manofthefield]

That new table makes a lot more sense... Looks like Pandy got her hands on it though with all that purple!

[Wrecent_Wryder]

D4

[dgyver]

150 mains with a full system and lunchbox/pods is great only if you like to run rich.

[Wrecent_Wryder]

[5

[dgyver]

Better yet...jet correctly.

[crispy5]

Anyone run a pre-2001 GS with a K&N lunchbox and a performance exhaust?

[werase643]

yes

[werase643]

Better yet...jet correctly.

preach on Brother D.
ya know you are just banging your head against the wall.....

[LostDog]

Glad to see others are adding info. There are now details for the 2001+ with lunchbox. If you have a different setup than what is listed you can add it inside the same box. Also, the tables are light blue, not purple...

[Wrecent_Wryder]

[4

[werase643]

Smartest thing you could do
I learned long ago....leave it alone til YOU notice a problem, then change it, better/worse.....keep on til you get better


what works at sea level dont work at 7000 ft

[dgyver]

Sorry, I tend to give a lot more credence to those who back up their stated opinions with facts, sources, evidence, lines of reasoning...     something...

When someone just tells you "what's right", and expects to you accept it, presumably because their authority is unquestionable, that doesn't leave much room for discussion. Doesn't matter what the subject is, there are always several of those, intoning the "truth" with solemn certainty.

Of course, they don't much agree with each other.

As I've said, I've got the jets, I'll probably experiment and decide for myself.

I have stated my reasons before but here is a recap.

When I bought my first GS it was a track bike. Thinking the jets were a little too small, I tried the suggested jets and the bike ran like crap. The mains were too big. I even had track workers commenting on running rich. Even on my 555 with high lift cams, I only ran 145 mains.

I learned jetting on 2-stroke 125 GP bikes. They are very finicky with jets as the temp and humidity changes. If you do not know what you are doing the bike will not run. I even had some advise from Ian Emberton. He called me several times from the UK discussing jetting. He was the tuner for Jason Desalvo (among many others) when he was running GP bikes. Anyone who races 125/250's, better be familiar with Ian E.


Most people think they are running rich/lean but they are looking at the wrong circuit. If you are not doing a plug chop then it is a waste of time pulling a plug. What they actual are seeing is the idle circuit. But they change the main because of this.

[The Buddha]

Well ... a cam or intake work will have an effect on jetting and not always need richer.
If you have a pipe and K&N you may squeeze more power with a leaner main jet, but streetablility means you give up that extra edge of power for better characterstics elsewhere, and winters and cold starts and quick warm up's are what you give up that extra bit of power for usually. Also on an 89-00 bike, you should check and set the floats back to the gasket level. If its high even 2-3 mm, 145 will act like ~150 ... I actually set them a shade under the gasket, they will always wear and go higher as the tangs bend and the needle wears. Next time I drive by, I'll see what it is you have done in your carbs that let you run smaller jets. My guess is that you run higher float levels ... which actually works fine cos when you run WFO all the time, it may not fill as fast. Now you run a cell in the tank right ... of course you ahve a pingel and a quick dry break line.
I dunno, somehting.
Cool.
Srinath.

[Wrecent_Wryder]

O4

[dgyver]

Jet how you feel is best. I have no desire to help with proper jetting anymore. The problem is that most do not really know how to tune carbs and what the proper order for selecting jets and other adjustments. It is not that difficult but takes some patience. So the blind selection of jets will work for the masses.

[Gisser]

Jet how you feel is best. I have no desire to help with proper jetting anymore. The problem is that most do not really know how to tune carbs and what the proper order for selecting jets and other adjustments. It is not that difficult but takes some patience. So the blind selection of jets will work for the masses.

 

I have differences with W_Wryder over carburetion but at least he's basing his assertions on empirical observation on his particular application.  Your criticism seems to be a projection from a different result attained on an engine with very different upgrades.  What the Guru said and more--cams, and especially bore kits, generate higher velocity in the carb venturi, which translates to lower air-pressure and a richer fuel draw in proportion to intake air volume.  The Bernouli Effect--even if W_Wryder doesn't believe in it.   IOW, you could very well need smaller main jets in a more radical application.   I've listened and no one has stated that 150's w/lunchbox kill acceleration at or near redline and that's the test of a main jet.  But with DIY carb jetting it's all a compromise....150's....shims....they can and probably will negatively affect other throttle positions....you choose your glitches. 

Bottom line is when it comes to DIY carb tuning A+B=C assumptions don't always hold true and are no substitute for one's own trial & error and thorough testing.              

[Wrecent_Wryder]

[4

[dgyver]

Gisser....my basis of jetting a GS is based on 6 or so different builds (exhausts, carbs, pistons, heads, timing, cams) of GS motors not just 1. My first experience with a 150 was with a stock motor, full Yosh & lunchbox. Open the the throttle fast and it would bog down. That has nothing to do with being on the track, unless no one ever opens the throttle fast on the street. Once I dropped it down a couple of sizes the throttle response was correct.