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  #1  
Old 28 Jun 2007
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lc4 exhaust rejet problem!

hello people, this is my first time on here!
i recently got an 05 lc4, my 03 got stolen a while back.... what a different machine the 05 is! does not have the same characteristics as my old one at all...
i have just fitted akrapovic end cans, baffles removed of course! the mesh airbox cover and the supplied 157.5 main jet... this sounds and looks great, but feels as though it has created a slight flat spot on quarter / thrid throttle... i thought i would raise the needle, but it is in the highest position already.
the "mixture" screw, i thought was for idle mixture only, therfore would have no effect on the riding mixture... is this correct?? does anyone have any suggestions for me regarding this matter

thanks in advance

gez
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  #2  
Old 28 Jun 2007
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The fuel mixture screw and float height affects idle and the first eight of throttle movement, as you keep twisting the throttle the jet needle regulates fuel flow up to about 3 quarter throttle movement then the main jet kicks in.. but there are overlaps.

my settings are these: sidecover screen,SXC end can, 165 main jet, jet needle lifted one notch, slide ports drilled out to 3 mm and EPC/SAS de activated

Starts and runs very good..
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  #3  
Old 9 Jul 2007
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needle and jeting

well its a world on it's own doing the tuning for the KTM....

dono about your German, but there is a very good web page K T M - S O M M E R they sale every thing you need, prepare Dakar bikes and so on...

well I try to explain... you got the sport-exhaust-system and the air-mash cover... well that's a start, but KTM don't tell you the right setup for the jets and needles.....
I guess you need the idle-jet 1.1 and a tuning needle !
at the end, in your case... ;o) you got the expensive parts already.....
the tuning needle part-no. [16254] for 12,90 Euro
consider to buy a extending fuel-mix screw part-no. [17410] for 20,50 Euro as well, that allow you to change the mix by hand without extra tools... ;o) it replaces the tiny STD adjusting screw, sticks out a lot and has a sort of T-piece handle on the end, very handy, all this together makes a big difference to your bike.
Ohh yes get your EPC-system deactivated if your bike is equipped with it... this EPC is only good to solve the emission law on the continent. to make it road leagle... sod it.... ;o)

to make it complete this posting getting a bit longer, sorry for that...

1st off all !!!!
forget altering any thing with a drill... !!!!
only use the right parts that are made for your carb or you may have to buy a new one and your fuel consumption is under no control !

OK here we go for all 640 Supermoto/Enduro/ADV - 1998-2002
------------------------------------------------------------------------------
Series setup:
idle jet STD: 1.2
main jet 142.5
needle STD: position 3rd from top / tuning needle: position 2 from top
air filter cover STD + STD-air-filter
exhaust STD

better setup with STD exhaust:
idle jet: 1.1
main jet 152.5 or 157.5
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + STD-air-filter
exhaust STD

better setup with Sport exhaust:
idle jet: 1.1
main jet 157.5
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + SM-air-filter
exhaust STD

better setup with Sport exhaust / ADV and travele setup:
idle jet: 1.1
main jet 155
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + STD-air-filter
Sport exhaust

better setup with Sport exhaust aggressive setup::
idle jet: 1.1
main jet 157.5
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + STD-air-filter
Sport exhaust

better setup with Sport exhaust racing setup::
idle jet: 1.1
main jet 162.5
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + SuperMoto-air-filter element
Sport exhaust


right.... now for all 640 Enduro/ADV - 2003-2006
-------------------------------------------------------

Series setup:
idle jet STD: 1.2
main jet 152.5
needle STD: position 3rd from top / tuning needle: position 2 from top
air filter cover STD + STD-air-filter
exhaust STD

better setup with STD exhaust:
idle jet: 1.1
main jet 165 + STD-air-filter
or main jet 167.5 + SM-air-filter remove the snorkel
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + STD-air-filter or SM-air-filter
exhaust STD

better setup with Sport / Akrapovic slip-on exhaust aggressive setup::
idle jet: 1.1
main jet 170+ SM-air-filter with or without snorkel removed
needle STD: position 3rd from top / tuning needle: position 2 from top
VA-air filter cover + STD-air-filter
Sport or Akrapovic slip-on exhaust and tuning db-eater


for all 640 SuperMoto - 2003-2006
---------------------------------------
there are more options to go for the SM Air-box, but as long you are riding 18" and 21" wheels and nobbly tires you don't want to know... it's a differed bike over all, only good for a short spin........ ;o)


----------------------------------------
well well, one tip if you try changing the idle jet... that one can be right a bastard, this little brass jet is hanging on to its carb and is tricky to remove, you may have to have a left-threaded bold remover or very hard edged spike handy in case the screw-slot from the jet comes off... as happened to me.... otherwise you are in trouble !
But one's you have changed the idle jet from STD 1.2 to the 1.1, you can start playing around with needles and main jets as you like to get the setup that match your need... ;o)
----------------------------------------

well a long post, but may help to find the right settings....
I ride a KTM 640 Enduro 2002 and use this settings and like it ;o)

aggressive fast throttle response, just nice...
idle jet: 1.1
main jet 162.5
tuning needle: position 2 from top
VA-air filter cover + SuperMoto-air-filter element + dustcover
SuperTrapp-Sport exhaust
with my 18L. fuel tank I can ride 340Km with this jetting, may not as good but I try to save up for the ADV tank....

I see you are in the UK, well I used to live near Oxford, no problems getting the parts ordered by KTM-Sommer in Germany, they do international deliveries.

have fun....
Spooky
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Last edited by spooky; 9 Jul 2007 at 19:31. Reason: typo and add-on
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Old 9 Jul 2007
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Quote:
Originally Posted by spooky View Post
well its a world on it's own doing the tuning for the KTM....

dono about your German, but there is a very good web page K T M - S O M M E R they sale every thing you need, prepare dakar bikes and so on...

have fun....
Spooky
add on to the web links.... some in English, but the 18 pages PDF-Tuning part is in Germen only, but has a easy to understand graph in it to find the jetting...

main page in English:
SOMMER KTM - ENGLISH INFO

Tuning samples:
SOMMER TUNING

to download the Catalogers:
SOMMER KTM - SPECIAL 07

emails and phone calls can be done in English, you will get an answer.. ;o)

well I'm happy with there service.... they seriously know what they are talking about.... ;o)

spooky
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Old 9 Jul 2007
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Nice and insightful post spooky

Just wanted to clarify about drilling the vent ports in the slide, this is probably one of the useful mods one can do to the BST40 carb and its free!

When you crank the throttle on a CV carb all you do is adjust airflow, the negative airflow above the diaphragm is what lifts the slide and supplies the fuel.

So what does drilling out the vents from 2.5mm to 3mm do?

When the diaphragm tries to lift the slide its somewhat hampered by the vacum from the cylinder, opening up these two vent holes equalizes that force to a degree.. I.E. the slide rises faster
You dont get more horsepower, it doesnt use more fuel.. it just reacts quicker in a way much like deactivating the EPC valve ( of course you do that mod as well )


This mod is described very well in this thread on advrider

For '05 640 Adventure owners... all 200 or so of you. - ADVrider
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Old 9 Jul 2007
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well you got me there ;o)

Quote:
Originally Posted by Laromonster View Post
Nice and insightful post spooky

Just wanted to clarify about drilling the vent ports in the slide, this is probably one of the useful mods one can do to the BST40 carb and its free!

This mod is described very well in this thread on advrider

For '05 640 Adventure owners... all 200 or so of you. - ADVrider
right... sounds good.....

but you know how fatal it can be for non mechanics to work on such parts of a motor...
well I used to build Rover V8 engines and blue printed timings.... please don't get me wrong with my statement.....

do you know any down side of this mod that effect the other jetting combination or is it just an over all improvement additional to the jetting....

there is one issue that makes me think about this mod.... there is a official mod around with a tuning slider in combination with a tuning spring, how they cal it... the spring has less windings and the vacuum ports are 2.9mm compare to the STD 2.5mm... now they are saying that this mod is no good for off-road/motocross or dessert washboard piste riding regarding the dancing effect of the slider coursed by the reduced spring tension ....

the official tuning-spring part-no.: [16160] for 9,40 Euro and the tuning-slider with 2.9mm bore [16261] for 29,60 Euro and typical used for SM street racer.

please let me know what you think about that.... well drilling the 3mm and using the STD spring may solve the problem...... but may still not a good idea for remote off-road and long distance traveling, well I still like the idea of cheap tuning and having an even better smooth throttle response....

only one thing to get straight... you are talking about the Mikuni carb for the LC4 are you ?

I acknowledge your commend.....

I know that KTM and other bike maker have to stay low on performance to retch the emission and road legal restrictions, making the over all setup more in the mid range rather than the optimum for the mass market.... the small bore of the slider would fit in that category...

spooky
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Last edited by spooky; 9 Jul 2007 at 23:40. Reason: more info
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Old 9 Jul 2007
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Hi again spooky
yes i am talking about the mikuni BST 40
i know some people has changed the carb slide spring for one softer sprung, this may cause bogging when going over rough terrain at speed, but will not affect reliabilty.. you just need to go a little slower, drilling out the vent ports will not affect other jetting on the bike.. it just reacts quicker, thats all


ps. if you find the bike bogs down in rough terrain, it may help to adjust the float height, if its too high the jetting becomes momentarily too rich and the bike stumbles.


Lar
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Old 11 Jul 2007
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Quote:
Originally Posted by Laromonster View Post
.... it just reacts quicker, thats all

Lar
Hi Laromonster

tack for det....

well I need anew slider anyway... why not banging in a mod one and use the STD spring for a start

spooky
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