98' 620 RXC W/Quicksilver carb

Discussion in 'Thumpers' started by Sailor Jack, Mar 4, 2005.

  1. Sailor Jack

    Sailor Jack Been here awhile

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    Hi, Just picked up a 1998 620 RXC with 3500 miles on it for $2800. Love it- feals like a scalpel compaired to the GS I reluctantly parted with a few months ago- The bike needs tires but other than that it's solid. It's also bone stock. With the carb I notice some intermittent engine stutter when running at low rpm at constant throttle position- is this normal for the KTM or an issue with the Quicksilver? Also since I'm new to the LC-4 any tips you might have on maintence and mods would be greatly appreciated!
    #1
  2. Jeff620RXC

    Jeff620RXC Been here awhile

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    There are issues with the Quicksilver.
    Some guys have spent some time and money on it and made it ok.
    Most consider it junk. Most guys swap in a Mikuni BST or TM40.
    The DelOrto came on the pre 97's and it is a pretty good carb.
    The ultimate replacement costs $500...the FCR 41. (you don't need the mx version)
    That is what I went with and there is no comparison between it and the E-Brock. It starts and idles perfectly. There is plenty power everywhere.
    It is the most expensive but the best performer. You can get a kit that comes with cables...and you use your current Quicksilver boots.

    You can send your Quicksilver to E-Brock and they will do some upgrades that help....I think it costs around $150. This may or may not make you happy. Mine had the mods when I got it and I could never get it to work well for me.

    http://www.pro-flo.com/proflo_keihin_fcr_carb_kits.htm#KTM
    www.sudco.com
    #2
  3. Sailor Jack

    Sailor Jack Been here awhile

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    Thanks for the advice. The guy who had the bike before me rebuilt the quicksilver and advised me to run it rich to avoid problems. It starts and idles without a hitch but has the problems i mentioned before. Whats a good carb/exhaust combo for this bike?
    #3
  4. g-force

    g-force Adventurer

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    i got the 170$ upgrade from edelbrock and though it looks super trick, it doesnt work like i think it should. bitch to start and lacks top end, but i am not sure if the top end problem is carb. warmed up it runs good enough though. i think i need exhaust before carb, whats the verdict on the big gun system?

    ps does yours vibrate like insane levels on the street in the pegs and bars?

    also check the flywheel, mine grenaded and shot magnets out the sight glass! i got a 180$ updated flywheel. luckily i was at work, at idle when it happened.
    #4
  5. Sailor Jack

    Sailor Jack Been here awhile

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    Yeah, it vibrates like a 25 cent bed at the tic-tock inn. My main complaint is the spotty fuel delivery- like I said consistant throttle + moderate RPM = engine stutter like fuel delivery is being interupted. I can't believe I complained about engine surge on my 1150GS..
    #5
  6. Jeff620RXC

    Jeff620RXC Been here awhile

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    I had top end speed problems with my Quickslobber....My bike topped out at 78 MPH...now with my FCR I can easily hit 100 with more throttle to go.

    I have the Supertrapp. It is the only pipe that is tuneable. You can add or remove disks. A lot of the guys like the IDS2....they have a removeable quiet core and spark arrestor too. It runs around $275 - $300.

    http://www.adventure-motorcycle.com/ktmlc4-ids2-quiet.html
    #6
  7. g-force

    g-force Adventurer

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    damn i was afraid of that. i need the top end i miss from my honda. i top out at more than 78, but it lacks the grunt it should have on the freeway.
    #7
  8. txrider

    txrider Been here awhile

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    My quicksilver went away too.



    Just dropped an FCR 41 kit from sudco on it last week and it runs great now, better than quicksilver or the 40mm Del Orto I replaced it with first.
    #8
  9. 2whlrcr

    2whlrcr gooligan

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    My 97 Duke had a Quicksilver. I suffered for three years with that carb and finally got tired of the surging. Sprang for the FCR41 and couldn't believe how much better the bike ran. Smooth and ALOT more power. I didn't think a carb could make that much power difference.

    Then I bought a 640 Adventure and decided to sell the Duke. I was too lazy to pull the FCR off of the Duke and put it on the Adventure before I sold it. Oh well, at least the Mikuni carburates cleanly, even though I know I could of had more power with the FCR.
    #9
  10. KTMRyder

    KTMRyder throttle jockey

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    I have a 97 and I got tired of fooling with that junk Edelbrock carb.
    just about the time I got it running properly it would change after a while for some reason. I think maybe the slide was wearing and causing problems.

    After it gave me starting problems on a Colorado trip I chucked it and got a BST like the newer bikes have. starts and runs great, no issues now. :thumb

    I thought about having the Edelbrock modified but, it seemed like throwing good money away on a piece of junk to start with.
    #10
  11. Sailor Jack

    Sailor Jack Been here awhile

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    Thats it! I'm springing for the FCR. Now to convince or deceive the wife...
    #11
  12. txrider

    txrider Been here awhile

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    FCR is great, but if cash is a big problem you should be able to fish up a BST from someone who went to an FCR, or ebay one. The FCR is kinda pricey.
    #12
  13. KTM950Wannabe

    KTM950Wannabe Adventurer

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    I have a 97 with quicksilver. Had the e-brock update...runs better, no surging, but a bitch to start and keep idle until it warms up.

    I would almost rather have the original back in...keep wearing my battery down.

    Anyone know of a fix to have the updated e-brock start better?

    Also had a magneto take a dump.
    #13
  14. Sailor Jack

    Sailor Jack Been here awhile

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    "Buy the best and cry once" someone once told me- I think I'll go with the Pro Flo kit.
    #14
  15. Shooter1

    Shooter1 Been here awhile

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  16. Sailor Jack

    Sailor Jack Been here awhile

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    Shooter, l'm willing to believe the BST is a huge improvement over the Q/S, and If you wander over a few threads to read Creeper and Meat Pops "ode to Mikuni" aka "The Great BST Challenge" it quickly becomes apparent that some people have an unusual, (abnormal) affection for the BST.

    What is involved in the conversion process? will a BST mount right up to my 98 620RXC air box? Do I need adapters/cables/boots? (Got part #'s)?
    The Pro-Flo FCR kit for the 620/640 includes adapters & cables and Jeff620RXC sez' I can use my Q/S boots, all for the not so low but not so ludicris price of $480. As for ebay there's a guy parting with an FCR 41, $300 current bid- no cables ebay favors the seller an I have no doubt the final price will be his $370 B-I-N price. Add another 70 for cables and 20 for shipping- no bargan there..
    #16
  17. txrider

    txrider Been here awhile

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    I'll back up the FCR kit, cables and carb already jetted. Was a bolt up dandy and used the QS boots just fine. Cable routing was the hardest part.
    #17
  18. Jeff620RXC

    Jeff620RXC Been here awhile

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    The FCR is an easy swap. I spent most of my time on the cables at the throttle...mostly because I had never had one apart (newbie).
    It comes jetted, close.
    I twisted once and hit the starter....it immediately started and purred so nice!
    I was giddy after fighting my e-brock for over a year.

    In the kit you also get the proper bell mouth (not sure what the technical term for that piece is).
    #18
  19. Sailor Jack

    Sailor Jack Been here awhile

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    I ordered the FCR kit from Pro Flo a few days ago- hope my order went through, (no email conf. as of yet) Also ordered up an IDS2 from adv-mtr- out of stock with a 2 week wait at best. Hope to have this project up and running before the end of the month. I am thinking about updateing the plastic- after I install the big orange tank the thing will have the color scheme of a cream-sickle.
    #19
  20. Jeff620RXC

    Jeff620RXC Been here awhile

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    Here is my 98 RXC with updated plastic and the 18L tank
    [​IMG]
    #20