If my mileage per tank has decreased by 30km

[3L4NS1R]

From my experience I would say you are now running way too rich.
What jet sizes did you go from, to ?
What mods have you made to your bike from standard that would necessitate richening your mixture ?

I believe stock is 124? Now at 128...

the 09 klx's are renown for coming from the factory running lean... so a quick mod with a dynajet kit should richen that up a bit...

[LBD]

Yep I agree but a bit peppier would be a bonus - esp if it is for nearly nothing...

cept he will be forever paying for more fuel....

[Tony W]

I believe stock is 124? Now at 128...

the 09 klx's are renown for coming from the factory running lean... so a quick mod with a dynajet kit should richen that up a bit...

Running a bike rich will 'probably'... increase fuel consumption, decrease power, and bore-wash your engine.

Did your bike run badly as standard ?

Have you "opened up" yor muffler and airbox ? This has increased both power and economy on our 3 new 05 Suzuki DRZ250s and 400. (back in 2005)
No change in jetting for 250, needle raised .75mm in 400. Extra 50 km per 10L tank on 400. (I did not measure the increase in the 250)

Are there any restrictors left in your inlet or exhaust ?

It sounds to me like you have headed in " not the optimum direction "

[3L4NS1R]

Running a bike rich will 'probably'... increase fuel consumption, decrease power, and bore-wash your engine.

Did your bike run badly as standard ?

Have you "opened up" yor muffler and airbox ? This has increased both power and economy on our 3 new 05 Suzuki DRZ250s and 400. (back in 2005)
No change in jetting for 250, needle raised .75mm in 400. Extra 50 km per 10L tank on 400. (I did not measure the increase in the 250)

Are there any restrictors left in your inlet or exhaust ?

It sounds to me like you have headed in " not the optimum direction "

Didn't run 'badly'. Was just constricted quite a lot (emissions laws overseas are very very stringent..)

Hmmm.. See, I thought it was better to run slightly rich than lean. Runs alot hotter if lean?

And yes, opened up the airbox as well, nothing done to the muffler yet, am considering getting a cycleworks exhaust for it.

[marks]

cept he will be forever paying for more fuel....

its a toy so less mileage is not an issue - less range is more of an issue so I might drop a jet size and see what happens.

[Transalper]

....And yes, opened up the airbox as well, nothing done to the muffler yet, am considering getting a cycleworks exhaust for it.

My understanding nowdays is that if you mess with one end you really need to mess with the other to keep it all balanced to make it work properly.
Only time I let someone talk me in to letting them mess with jetting and airbox on one of my bikes I hated the way it ran and sounded. The mechanic couldn't smooth it out, I couldn't afford more open flowing pipes and didn't want it any louder. Probably did need exhaust work to help the outlet end match the intake end, so put we tried to put it back to stock jetting, patched the airbox etc but never got it nice enough again so it's gone now.

[3L4NS1R]

My understanding nowdays is that if you mess with one end you really need to mess with the other to keep it all balanced to make it work properly.
Only time I let someone talk me in to letting them mess with jetting and airbox on one of my bikes I hated the way it ran and sounded. The mechanic couldn't smooth it out, I couldn't afford more open flowing pipes and didn't want it any louder. Probably did need exhaust work to help the outlet end match the intake end, so put we tried to put it back to stock jetting, patched the airbox etc but never got it nice enough again so it's gone now.

Yeah, that would suck! As they say, you never know what you've got till its gone...

In my case, I just got fed up with the lack of power from the klx, and I've come to enjoy the whole tinkering aspect of it... now I just have to learn how to tinker!

[warewolf]

Yep I agree but a bit peppier would be a bonus - esp if it is for nearly nothing...

cept he will be forever paying for more fuel....

+1. That's one reason I have not rushed in to uncorking the 640A. As delivered in Euro-II emissions compliance, at low-mid rpms it's too much of a pussycat not the wildcat you'd expect from a big-bore. Heck it's even got gearbox switches to deny you full power in 2nd & 3rd gear!! This is more of an issue in rough conditions when you need power NOW to cope with a hazard. The mods are not pricey, but 25% worse fuel economy is frequently reported. So I got a spare stock exhaust to destroy modify in case I want to change it back. In the meantime I use the throttle and gearbox to give the power I want.

If you're not hitting or holding full throttle regularly, chances are your bike obviously makes enough power - ya just gotta use what's there. More likely to happen with a 250 than a big-bore; my DR-Z250 sure spent a lot of time at full throttle. But more grunt lower down the rev range is always nice which in itself can contribute to worsening fuel economy even if the bike is running better and returns better economy in a steady-state cruise.

Have you "opened up" yor muffler and airbox ? This has increased both power and economy on our 3 new 05 Suzuki DRZ250s

Modern bikes are pretty well sorted in that department; those bikes are particularly reknowned for having bad exhausts. Plus the DR-Z250 is essentially unchanged from at least 1995, maybe earlier.

Hmmm.. See, I thought it was better to run slightly rich than lean. Runs alot hotter if lean?

You're talking a lot leaner than ex-factory. Going horribly lean by fitting a wildly open exhaust and/or similar drastic airbox mods, without re-jetting... yep, sure, you're headed for trouble. You're probably doing more damage being overly-rich. Generally to tune your main jet, you go one jet richer than the one producing best power = slightly rich = safely rich. At other places in the throttle/rev range, mostly you need a bit more richness when you crack the throttle open, for more immediate response. This is the main area we as riders conflict with the emissions people; they are trying to remove ALL excessive fuel conditions as a priority over response.

Tuning can be rewarding, and a classic case of the more you know, the more you realise you know nothing... The kits are supposed to take the trial-and-error out of it, indeed it is their expertise you are buying as much as the hardware. But every bike is different, and then you get environmental vagaries like the US/EU fuels being a different density to ours so the jet selection may be different, or their bikes are set up differently.

[3L4NS1R]

You're talking a lot leaner than ex-factory. Going horribly lean by fitting a wildly open exhaust and/or similar drastic airbox mods, without re-jetting... yep, sure, you're headed for trouble. You're probably doing more damage being overly-rich.

So how can I tell if I'm running rich or lean?

[marks]

Heck it's even got gearbox switches to deny you full power in 2nd & 3rd gear!!

they were much cleverer with the klr - they used their nogins and designed the engine to restrict the power in 1st, 2nd,3rd,4th and 5th - no silly switches needed

[Eddieb]

So how can I tell if I'm running rich or lean?

Take it for a good ride, then pull the spark plug and compare it's colour and condition to pics found in most Haynes manuals and probably online.

[3L4NS1R]

Take it for a good ride, then pull the spark plug and compare it's colour and condition to pics found in most Haynes manuals and probably online.

ah ha. Ok. Cheers!

[MXNUT]

Going from a 124 to size 128 jet is not a large increase.This sort of increase will certainly not be enough to cause any bore wash issues.

[Tony W]

So how can I tell if I'm running rich or lean?

By the density of the "soot" build-up on the inside of the end of your muffler.
Nordie boy posted something about this last week, I can't remember where, maybe he could give you some advice.

As usual, Warewolf makes some very good and helpful technical points.

I would jet your bike back to standard at this stage until you do your muffler mod.
No power will be gained until you free the flow up at that end.
You can then start experimenting.

It sounds at this stage, you are doing damage to your bike.

Good luck.

[warewolf]

I believe stock is 124? Now at 128...

Did you check if you were changing measuring systems? A DJ128 is a lot bigger than say a Mikuni 128.

So how can I tell if I'm running rich or lean?

Pull the choke on to add fuel; if performance improves you were lean. Take the airbox lid completely off to add air; if performance improves you were rich. Crude but may work; some of the best dyno tuners use it.

It sounds at this stage, you are doing damage to your bike.

Would have to be a long way rich (for a long time), but possible with a DJ 300 kit in a 250. Depends how well tested the published mods are... this has come from advrider or some other source, right? Empirical data is usually more accurate than emotive.

There is heaps of stuff on the interweb about tuning. Sites like thumpertalk have "how to" documents which can be a great help, often 'stickies' at the top if there is not a specific tech forum. You could even try ktmtalk, as the basic information is the same. I don't frequent kawasaki forums so can't comment on them, but chances are they'll have similar info available. Also try your local library, they should have a few books on tuning; I found a couple that were recommended on thumpertalk.