640 FCR 37 install

Discussion in 'Thumpers' started by gunnerbuck, Oct 16, 2012.

  1. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    5,140
    Location:
    N.V.I, B.C.
    I believe some of the KTM FCRs dont have the power Jet {leak jet} which lessens the pressure to the A.P... The carb I have is equipped with this feature so it already doesn't have a full pressure squirt and I still have a larger leak jet to try.... The thing I have to figure out is if it is dying on the throttle snap because it is getting too much fuel or not enough...Between the plunger timing screw and the leak jet it should be solve able... But that is for another day as I have spent more time and money than expected on this project already, back burner it goes for a bit...
    #21
  2. Droptarotter

    Droptarotter Long timer

    Joined:
    Jul 11, 2007
    Oddometer:
    1,486
    Location:
    Cloverdale,BC
    Gunner;
    I have been watching your exploits on this carb swap intently as I was thinking of doing the same.
    So.........as per your quote...........in hindsight, would it just have been easier to buy a new carb already set up for the 640??
    Most of us like to tinker, but with some projects there comes a time when enough is enough.
    Any comments?

    Cheers
    #22
  3. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    5,140
    Location:
    N.V.I, B.C.
    If you count the labor involved as an expense then yes buying a new carb outright is probably cheaper the first time... But if somebody does the legwork and puts out the info on parts needed, jetting and fitment issues then the carb can be setup for a one off install... Remember, even if you buy a new carb you will need to have the jets set up, get the proper airbox boot and buy a set of throttle cables unless your willing to bend up the bst units... Also a used FCR 37 can be had for $100 if you wait for the right deal as to where a new one puts you back $400-$500 right from the get go... Add an airboot and cables and there goes another $60-$100...

    My biggest beef with installing the FCR is the size of the thing... It is really tight to fit it in there and you have to move some electrical and shift the hose routing to make it work... Also the throttle cables run right into the forward right frame backbone so you either have to route them above it or below it which kinda kinks the cables a bit... When I get to the final install I will likely run the cables under the backbone and think about running with the cover plate off so the carb will stand straight up....
    #23