Which carb is best on LC4 640

Discussion in 'Thumpers' started by losiu, Sep 19, 2006.

  1. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    How do you have the bike tuned-which lights for idle, interstate cruise, and hard acceleration now that you can compare it with the Power Commander?

    Thanks,

    Dirty
  2. potatoho

    potatoho Cheese and Rice!

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    On the LC4, which didn't have EFI or Power Commander etc, I had it reading top green and I was satisfied. It was very risilient so you could put the reading just about anywhere and the motor would still run smooth.

    When I started with the LC4 readings, the main issue the motor had was an extreme dip at off-idle. It dove below the greens for a brief position on the throttle, and that extreme caused the motor to stumble. This was because the needle was worn and it had to be run in the lower clip positions. With a new needle I could run at the proper clip and the off-idle mixture wouldn't dip. That's the critical issue for the BST is to make sure there isn't that off-idle dip because that's where the slide begins to move and it's so easy to have an imbalance at that point on the CV carb.

    The other issue on the LC4 was an intermittent leak at the silencer joint. That caused fluctuating jet4power readings at certain speeds. It made the motor have a slight vibration rumble in the mid range. It was an aftermarket (ids2) joint which doesn't fit airtight. I sealed it up with high-temp silicone tape. Cleared up the errant readings and the motor, for the first time in fact, ran smoothly in the mid range. Quite a treat!

    The PC is on the Husky. I made a few maps since for some reason the stock PC map was nonsensical. So I made a zero map and the first thing I did was normalize the mixture by doing roll-ons and checking for any weird jet4power lights. In fact on that bike there was a huge dip between 3500 and 5000. I made a zero map with that area corrected and this got rid of the goofy stumbles the motor had at certain rpms. This was all just normalizing it to the top green light, which required a +4% increase between 3500-5000.

    That pretty much fixed the Husky. Was terrible prior to that. Big power hole. Then I just experimented a bit below 3500 and made some progressive maps (progressive from lean to rich below 3500) to try out during rides. So I had maps which were mid green below 3500 to give a bit softer off-idle, and some at top green to be more torquey.

    The PC also has an accelerator pump emulator, which is configurable. Unfortunately not configurable via the LCD unit, so I had to connect it to a computer to change that setting. The a/p setting lets you increase the responsiveness of the system by temporarily increasing the fuel level based on throttle movement. Same as a mechanical unit but it's all software. The EFI computer obviously has some of this logic already, but I've felt it was rather muddy, and the PC a/p lets you make the power more crisp.

    However the bike (Husky TE450) pisses me off because you cannot ever make it smooth without the counterbalancer, and if you make it above 7krpm you are just miserable. The LC4 was smooth as glass above that with my G1 cam.

    Anyways, regarding lights. Another unexpected thing I noticed while using the PC. I did some highway runs and experimented a bit with running the mixture +/- on the Husky. I could move the mixture even -10% at 70 mph and honestly could not tell from seat of the pants. I really expected to be able to notice, such as maybe a tone change or an increase/decrease in rpm. Nope. The only thing which changed was the jet4power reading and a bit of change in ability to accelerate. In fact, I was pretty disappointed in that I could not "fix" everything by correcting the air-fuel. The air-fuel was only a factor, but not the solution to that Husky motor.
  3. azzad

    azzad Adventurer

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  4. potatoho

    potatoho Cheese and Rice!

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    Along this theme, I took my TE450 out today. I'd sorta shelved it for a year or so. I'm still messing with the "jetting".

    It's not so much effort to get a proper air-fuel for each unloaded rpm. It's all the acceleration-driven mixtures that are what make one bike outperform. That's the special sauce of custom needles and of EFI maps. Correcting the air-fuel during acceleration.

    What they do with the Power Commander (via tuning centers), is they create a column of trim values for each position of the throttle. With the use of a dyno, they constant position the throttle and assign a dyno load to bring the motor to the low rpm of a range, then they decrease the load until the motor accelerates to unloaded rpm. AFR trim values are calculated for every 250 rpms as the motor accelerates. They repeat this test for each throttle position column.

    With these trim values, they are providing multiple air-fuel corrections for a given throttle position as the motor accelerates. With a proper map, the air-fuel dips which are seen during hard acceleration can be reduced.

    I have heard some positive things about the new Power Commander V with the Auto Tune. Auto Tune is an optional wideband sensor, which when you enable a learning mode, will create trim values which correspond to the acceleration patterns you used during your ride. So in theory it can create a similar map to the dyno load technique, or perhaps it might even make a better one.

    Still, I'm not sure if I will spend any more money on this TE. I already have to upgrade the ECU firmware, upgraded iBeat software, and now probably need to upgrade the Power Commander. Sheesh. EFI sux.
  5. wind pusher

    wind pusher WIND PUSHER

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    Hello Gents,

    I have an 06 640A and have done all crepers mods.

    The problem is the off idle stalling, the needle looked good. Can the air fuel screw cause this?

    Please help!:huh
  6. gunnerbuck

    gunnerbuck Island Hopper

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    A few things are possible... There could be sediment in your floatbowl that temporary blocks the main jet... Your float needle valve assembly or o-ring are no longer doing their job and need replacing.... Your jet needle has suffered from wear.... Float height needs adjustment...

    I would suggest to take the carb apart, inspect and do a thorough cleaning...http://www.advrider.com/forums/showthread.php?t=347184
  7. Tseta

    Tseta Lost

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    In addition to gunnerbuck's suggestion about checking and cleaning the carb, the original problem description sounds like the EPC could be to blame. This is especially if the problems occur only in second or third gear.

    If it turns out that the EPC is (at least partly) the culprit, a good guide for removing it can be found here.

    Cheers,

    Tseta
  8. gunnerbuck

    gunnerbuck Island Hopper

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    Good theory Tseta... I would of never thought of that as I do not have the EPC stuff on my 03 engine... I guess that stuff came to North America on some of the later models....
  9. Sniper X

    Sniper X De Oppresso Liber

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    I vote for the FCR41 with a well tuned accelerator pump circuit.
  10. Shooter1

    Shooter1 Been here awhile

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    Have you considered an S&S? .......

    Harvey
    #1017
  11. Mo-Tarded

    Mo-Tarded Been here awhile

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    An S&S being a carburetor ? ...or are we merely switching self-centered subjects indiscriminately ? Just asking....
  12. Knobbiethrower

    Knobbiethrower ADV in ADK

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    Can any 41mm FCR be bolted up to my 05 640 ADV? What do I need to do for the conversion to replace the BST? Or am I forced to buy from Sudco with the LC4 kit?

    Looking for detailed advise from anyone that already has done this swap.

    Thanks!
  13. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Believe it or not, Mikuni has more than a few variations of the 39 and 41mm FCR carbs.

    Both carbs mentioned above are both physically the same size/different bore sizes/but the big 4 Japanese makers use Mikuni carbs that sometimes cause fittment problems for the guys that source them and try to mount one on their LC4.

    It's best from everything I've heard to stick with an FCR taken off another model KTM.

    Fittment issues with carbs off of Japanese bikes fitted onto an LC4 mainly involve clearance/interference between the accellerator pump and head pipe.

    Dirty
  14. Knobbiethrower

    Knobbiethrower ADV in ADK

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    Thanks for the tips Dirty, but I'm looking for someone to chime in with detailed specifics ( for dummies like me ) so I can reduce my trial , error and $. TPS mods etc..
  15. ChrisC

    ChrisC Amal sex?

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    Seems to me there's a cack-ton of info on this topic in the Index... :deal
  16. Laromonster

    Laromonster Lean, mean pacifist machine

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    I dont believe it


    Keihin... :evil
  17. laramie LC4

    laramie LC4 flying something...

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    yup- keihin not mikuni

    not that mikuni doesnt make pumper carbs as well, just not as popular. as for variations of the FCR, there are at least 3 different generation of the FCR and that doesnt count the diff between teh MX and non-MX versions. the main key to finding one that will work in your 640 is to find one that came out of a KTM origionally. make sure that you get the throttle cables along with it while your there.

    laramie :beer
  18. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Opps, blame it on the grey..no, make that titanium hair.

    Keihin

    Dirty
  19. meat popsicle

    meat popsicle Ignostic

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    There's even a thread by creeptastic on fitting up an FCR to an 03 LC4, including a comment on hooking up the TPS (but not a step-by-step how-to).
  20. outfront

    outfront Adventurer

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    Can someone direct me to that thread? Ive hunted this site for a step by step, no luck. Maybe I need a step by step, using the search feature.

    I just purchased a used FCR 39, model 016-740, with cables from an 01 LC4. $ 175.00 . Im told this carb came from Sudco.

    I contacted The folks at cycle works, to see if this carb would work on my 03 640 Adventure. Below is there responce.

    An 03 requires the 016-740A kit. The difference between the 016-740 and 016-740A is just the cable set up. In 2000 KTM changed their throttle housing. 016-740 includes the 021-291 cables. 016-740A includes 021-280 throttle and 021-281 cables. We can order the throttle and cables for you and then ship them by Thursday if you like.



    It would be helpful if I had a step by step procedure.

    Thanks.