LC4 640 starter clutch fix

Discussion in 'Thumpers' started by losiu, Apr 17, 2007.

  1. philosobrad

    philosobrad problem_solvent

    Joined:
    Sep 5, 2006
    Oddometer:
    173
    Location:
    Springfield, MO
    I swear, under penalty of flogging................

    By the way, I killed a printer by printing out this damned manual. Would have been cheaper to source one on fleabay :)
  2. slackmeyer

    slackmeyer Don't mean sheeit. .

    Joined:
    Jul 23, 2007
    Oddometer:
    3,626
    Location:
    Berzerkeley, CA
    Maybe someone will have an idea about this here:
    Last winter, my bike got rebuilt, the whole shebang, crank bearings, piston, cylinder hone, etc. I took the starter clutch out and tightened the sprague clutch spring, and stopped the screeching noise it would usually make, too. So the bike runs great. Also, rebuilt the carb with new parts from Derek. So the bike runs great, usually starts with just a couple kicks. . . . but the damn thing won't start from cold on the electric start. Once it's warm, the electric start will fire it right up. And the weird thing: the starter turns the bike over just fine, it just doesn't fire up. Probably a carb issue and not a starter issue, but maybe someone has an idea?

    Oh, and I'm also running the Denso spark plug that Derek recommended, sometimes I wonder if the spark isn't quite strong enough when the starter motor is working. . . .

    Any ideas?
  3. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,610
    Location:
    Traveler
  4. slackmeyer

    slackmeyer Don't mean sheeit. .

    Joined:
    Jul 23, 2007
    Oddometer:
    3,626
    Location:
    Berzerkeley, CA
    Yeah, I've been following that. I think you're right, that's where I'll start: I mostly just reset the carb to previous settings when I put it back together (like I said, once it's running, it's great. . . . wheelies in third, and 50mpg all the time).
  5. wrk2surf

    wrk2surf on the gas or brakes

    Joined:
    Dec 16, 2007
    Oddometer:
    7,782
    Location:
    THE exact center of California/Bass lake/Yosemite
    perhaps you should replace that sprague? thats where I would start..
  6. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,610
    Location:
    Traveler
    Brad,
    Puller's in the mail to you.
    bill
  7. philosobrad

    philosobrad problem_solvent

    Joined:
    Sep 5, 2006
    Oddometer:
    173
    Location:
    Springfield, MO
    10-4
  8. dog'meat

    dog'meat Presidient

    Joined:
    Sep 4, 2008
    Oddometer:
    168
    Location:
    Cromagna
  9. DirtBikeDaddy

    DirtBikeDaddy DBD

    Joined:
    Dec 11, 2010
    Oddometer:
    16
    Location:
    Thumper
    OMG...

    I finally did the Sprauge fix but something else is wrong now???
    Yes I'm slow @ getting anything done!

    Pulled everything off & out last year, but had to pack up the garage for the season!

    ...9 months later and here I am...

    buttoned everything back together and waited for some guts to hit the e-start. Guess what happened?

    Nothing, LOL.

    Well that's not true, starter motor got REAL hot, headlight went dim...

    Stopped at that point and decided, I must have assembled the sprague assembly backwards, the new spring was installed and all the odd shaped pieces installed with somewhat smooth finish.

    Checked this afternoon (yes I pulled all the covers off again) and it seems to match the picture in post 1 (way up there) and I'm (yes I'm not very mechanically gifted) wondering what I've screwed up???

    You all must be laughing your A55 off at me today...it's ok, it's good to laugh..LOL

    The main gear that inserts into the sprague assembly, is turning in only one direction, that is (excuse my poor mechanical lingo) clockwise turns shaft (if the shaft key was removed) but counter-clockwise turns freely.

    ok...when your all done laughing...tell this sparky where I went wrong!
  10. Bob

    Bob Formerly H20Pumper

    Joined:
    Sep 25, 2002
    Oddometer:
    3,094
    Location:
    Corral de Tierra CA, Ketchum ID
    Duh, you do realize if you woulda bought an XRR you wouldn't be having this problem!
    When you figure it out you'll be happy to not be kicking it.

    Did you try to pull in the compression release first?

    I'm sure a real mechanic will be along shortly.

    Good luck
  11. DirtBikeDaddy

    DirtBikeDaddy DBD

    Joined:
    Dec 11, 2010
    Oddometer:
    16
    Location:
    Thumper
    what is that???

    hahaha...made you look!

    Yes, I did!

    *waits for a mechanic
  12. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,610
    Location:
    Traveler
    Willit turn over with the kick starter?
    b
  13. DirtBikeDaddy

    DirtBikeDaddy DBD

    Joined:
    Dec 11, 2010
    Oddometer:
    16
    Location:
    Thumper
    Yep, spins the shift anyways.
    Sounded Norman bit didn't keep kicking until she started or anything.

    Sent from my Nexus 7 using Tapatalk 4 Beta
  14. DirtBikeDaddy

    DirtBikeDaddy DBD

    Joined:
    Dec 11, 2010
    Oddometer:
    16
    Location:
    Thumper
    So no mechanic ah?
    Oh well!

    Sent from my Nexus 7 using Tapatalk 4 Beta
  15. Reset1

    Reset1 640-24-7

    Joined:
    Oct 16, 2007
    Oddometer:
    72
    Location:
    south africa
    after all this, when reassembling, how much newtons should the engine case blots (4 outer M8 ones) be torqued?
  16. F1paul

    F1paul Adventurer

    Joined:
    May 3, 2013
    Oddometer:
    46
    I believe somewhere above was said the four M6 (8mm) should be torqued to 8nm
  17. bikemoto

    bikemoto Tyre critic

    Joined:
    Oct 24, 2004
    Oddometer:
    2,841
    Location:
    Nelson, New Zealand
    Please! stop calling the bolts M8. They are M6. The number refers to the thread diameter in mm. NOT the bolt head size. I'd really hate for someone to skim-read this stuff and try to torque an M6 up to M8 values.

    Most M6 are 10 Nm.
  18. F1paul

    F1paul Adventurer

    Joined:
    May 3, 2013
    Oddometer:
    46
    So finally had the time to pull my flywheel off to inspect sprag clutch and it is definitely my problem... The spring is visibly stretched looks worse than loisus...
    I was wondering tho if it would be OK to run the bike without the sprag installed back onto the flywheel as I'm still sourcing the oils seal for the spring...first one I bought was their skf#19993 interchange part but the spring was too thick ....I have on order an skf but have to wait a week and I'm jonesing to ride.
    Haven't been able to ride cause kick start was turning starter motor and all and my quads are just not big enough ��
  19. LoopGaroo

    LoopGaroo Been here awhile

    Joined:
    Nov 22, 2010
    Oddometer:
    333
    Location:
    Madison, WI
    I'm about to tackle this project on my '02 640Adv. I just wanted to confirm that that it's okay to use the bolt from the front of the engine to lock the crankshaft in place when removing the flywheel?

    And, will I need any special tools besides the flywheel puller?
  20. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    5,140
    Location:
    N.V.I, B.C.
    No, the 02 has the newer ignition with a high flywheel torque value. Using the locking bolt may damage the crank