LC4 Won't start

Discussion in 'Thumpers' started by Supervaca, Jul 22, 2010.

  1. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    I just bought a new to me 625 sxc as a "some assembly required" deal and now after assembling it it won't start. The bike is a 2002 sxc with a 2005 625 high flow head motor and Keihin fcr 41 carb.

    The motor, electrics and carb have never been mounted together before meeting up on my bike, but they are supposed to have all worked where they came from.

    So here is what happens... nothing. not a single detonation no matter how much i run the starter, the engine turns over and sounds as if it's just about to start but no dice, the exhaust pipes get hot but i don't even get a single proper fart.

    I'm running out of things to do, short of tearing the valve cover off and checking if a previous owner installed the cams wrong.

    Here is a list of what i have tried so far, any ideas are welcome.

    1. Checked that there is spark = Good strong spark

    2. Pulled and cleaned the carb = all clean, fuel screw all the way in and 1.5 turns out, the main jet is a 168 and the needle is in the 4th out of 7 clip

    3. Air filter is clean.

    4. The plug comes out wet after trying to start.

    5. I have tried a different CDI that i borrowed from a mate, no difference.

    6. I have tried spraying some dieselstart into the airfilter box, not a cough.

    7. I haven't done a proper compression test yet but with the plug out it will blow your hair back.

    8. Checked the electrics and all my ground connections.

    9. Disconnected the decompression lever and throttle from the handlebars to be sure they are not being pulled.

    10. ??


    So there it is, what am i missing? on my old XR600 the automatic decompressor could get stuck and give this problem, but i guess i won't know without a compression test.

    Any help you guys can give me will be welcomed with open arms, I'm really looking forward to riding this bike and i feel like i have tried everything, so thanks in advance.

    Supervaca
    #1
  2. Blakebird

    Blakebird Solo Backwardo

    Joined:
    Feb 7, 2004
    Oddometer:
    18,500
    Location:
    Parker, CO
    good spark, but when?
    timing?


    I agree on checking the cam timing too.
    #2
  3. makazica

    makazica Been here awhile

    Joined:
    May 17, 2008
    Oddometer:
    770
    Location:
    Zagreb, Croatia
    Check timing, valve lash, use fresh fuel and kick it 20+ times before actually trying to start it (of course, with the ignition key on off). Also before you try to start it up the idling speed.....
    #3
  4. bmwktmbill

    bmwktmbill Traveler

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    Spark?
    Tighten the spark plug cap to the wire.
    Try a different plug.

    Ask yourself this.
    When the piston is at TDC(top dead center) are both valves closed, that is do they have clearance(loose)?
    Next the intake valves should open, then the exhaust valves open, then back to TDC.

    And,

    Is the float level correct,
    It is?

    Are you positive it is gas on the plug not oil(oil level is correct)?

    If all this is correct I think it has to run.
    And that's all I can think of.
    bill
    #4
  5. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    I do get spark when i have the plug out, I'm not satisfied that it's strong enough som I'll get a new plug tomorrow, the one i got today wouldn't fit.

    I also tried grounding the engine directly and that didn't help.


    I tried emptying the carb of gas and spraying diesel start directly into the intake side with the airfilter off = not even a fart, to me that means that it's not a fueling problem but rather a spark/compression problem.



    It really seems like i have to open her up this weekend and check all the timing marks..

    oh well at least i get to know my new bike :)
    #5
  6. wrk2surf

    wrk2surf on the gas or brakes

    Joined:
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    actually shorten the plug wire ... new plug and make sure the gas is on:lol3
    #6
  7. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    She farted :)

    went to the workshop today and tried a new spark plug, with the new plug i noticed several things.

    1. with the old plug inthe engine and the new one out and grounded... no spark. when i pull the manual decompression i get spark but when the starter has to pull the engine with compression(old plug in) I'dint get any spark, so this is probable what has been happening all along due to me only having one spark plug. i pull it out to check for spark and since it's out and there is no compression i get plenty of spark, but as soon as i put it back, no spark..

    So i out the new plug in, emptied the carb, opened the throttle fully and gave her a good squirt of diesel start directly into the carb and...

    Got two massive farts :):):) so the valves and timing must be at least somewhat correct..

    Battery is on the charger right now so tomorrow I'm hoping for more than just a few farts.
    #7
  8. bmwktmbill

    bmwktmbill Traveler

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    I would still consider a timing problem. When a machine is way off time that's how they act, just a couple of explosions.
    Random.
    bill
    #8
  9. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    Ok I'm back from hours and hours in the workshop :(

    the situation now is very weak/no spark compression is fine and i spoke to the guy who assembled the motor and he assured me that the timing is correct, he's done a lot of these so I have no reason to doubt him.

    Back to the spark problem, i get 1 weak spark then no spark when i crank the engine with the starter and a plug in my hand(grounded of course) and one plug in the engine just for compressions sake, when i pull the manual decompression and crank it i get weak orange sparks, in other words at no time do i get a good fat blue spark.

    here is what i have tested

    Changed the wiring loom to a completely new one = no change
    Ran the starter off a different battery = no change
    Kick starter = weak orange spark
    swapped CDI with an extra i have = no change
    swapped rectifier with an extra i have = no change
    swapped capacitor = no change
    cleaned all connectors = no change
    charged the battery fully = no change
    grounding the motor directly to the battery = no change
    grounding the coil directly to the battery = no change
    cut 1/4 inch off the sparkplug cable and screwed it in tight = no change
    New plugs, both a dpr8ea and a d8ea = no change


    if i put the bike in gear the starter is disabled and i can't crank the bike, and i don't think there are any other cut out circuits and if there are they shoul prevent me from cranking not just kill the spark.


    measured the pulser coil = 120 ohm's which is within spec
    measured the stator 0.9 ohms on all three to one of the other three and no connection to ground on any of them.

    the only thing i havent tried swapping is the ignition coil so maybe thats what's next?
    I'll try to tage my CDI to the dealer tomorrow and see if they can test it for me.

    anyone have anything else for me to try? I'm really getting quite desperate here.

    thanks
    Supervaca
    #9
  10. Luke

    Luke GPoET&P

    Joined:
    Aug 25, 2004
    Oddometer:
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    Location:
    Beaverton, OR
    How about the ignition coil?

    The manual says:

    blue/white - ground 0.425-0.575 ohms
    blue/white - ignition wire 10.8 - 16.2 Kohms

    Spark plug connector: 3 - 7.5 Kohms




    Question: Does your stator connect to the wiring harness with just a 3 pin connector, or is there both a three and a two pin connector?
    #10
  11. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    Hi Luke

    My stator has both a 3 pin and a 2 pin connector.

    i managed to get the bike started yesterday by towing it, but it was very weak and sounded like it was drowning (probably from the weak spark). I got it back in the work shop tonight and put my scope on it but couldn't see anything new. I measured the all the coils and they all check out.

    I still get a very weak spark, so now I'm looking at three possibilities.

    1. Both the cdi's I have are busted in the same way, giving me a spark but a weak one (i don't find this very likely)

    2. The wiring harness i got for the bike is somehow wrong and I'm lacking a connection somewhere that would give me the powerful spark and the weak spark is a result of this.

    3. The ignition coil is faulty and is messing up my spark.

    i have a friend coming back from vacation on Monday who has a new coil for me to test out, after that ill be left with 1 and 2 on the list.

    any suggestions?
    #11
  12. GodSilla

    GodSilla I did that.

    Joined:
    Sep 21, 2006
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    8,665
    Location:
    Downtown S.E. NSW
    Bad frame earth?
    #12
  13. dlh62c

    dlh62c Long timer

    Joined:
    Jan 11, 2006
    Oddometer:
    1,603
    Check the cap that connects between the plug and the ignition wire. I had corrosion in mine where the cap and wire connect. I trimmed about 1/4" off the wire and reattached it. There's a screw in the cap that you thread into the wire.

    My spark plug cap had a large chip missing under the rubber seal. I'm purdy sure moisture was getting in there causing the corrosion. The bike would start and idle fine, but when I rolled on the throttle, it would sputter and die.

    On my 07 ADV the cap is spec'd at 5k ohms, its also marked as such. When I measured the new one, it was 4.82K, when I replace the old one I'll measure it out to see if it measures the same.

    Bear in mind that you may have more than one faulty component on your hands. With that being the case, troubleshooting can be a real pain.

    http://www.randakks.com/TechTip83.htm

    http://www.dansmc.com/cdiignition.htm

    daryl
    #13
  14. bmwktmbill

    bmwktmbill Traveler

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    Squeeze the fuse holder connections tight for good contact, especially the main fuse. My main fuse losened up and the bike acted like yours. Squeezed it with a pliers and all was well.

    bill
    #14
  15. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    :clap

    I found something wrong! finally.

    After testing and testing again i had a buddy come up and help me today and we got something.

    The black wire coming out of the stator is dead on cranking the engine with the starter and the decomp pulled i get the following measurements

    yellow to black/yellow 0.9 ohms on cranking 7 Volts
    red/black to black/yellow 0.9 ohms on cranking 7 Volts
    red/black to yellow 0.9 ohms on cranking 7 Volts

    the manual says 0.9 ohms and 17 volts +-1 so i think there is something wrong here.

    secondly

    yellow to ground 7 volts
    red/black to ground 0 volts the manual specs 12.5 volts
    black/yellow to ground 7 volts


    so what do you think? I'm getting a new stator tomorrow to test and will let you know how it works out, but could this be the cause of my weak spark?

    I did squeeze the main fuse holders so those are good and i put a new ignition coil on today with no difference.

    update thursday.
    #15
  16. dlh62c

    dlh62c Long timer

    Joined:
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    Oddometer:
    1,603
    Way...Way COOL!

    Take notes as your doing this and measure out the new parts, This will give you a baseline for any future problems.

    daryl
    #16
  17. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    Thx Daryl, as i said earlier, i might not like it right now but i sure am getting to know my bike. I have all the values in a spreadsheet for later use.



    So, i finally got her started and ran her a bit (10 minutes) and I lost a LOT of oil into the air box.

    The bike feels very weak and still can't start unless i tow it.

    The big question is, why am i getting all that oil in the air box?

    and is the LC4 motor supposed to blow really hard out through the breather hoses (connected to the horizontal frame tube connected to the air box).

    the oil level was spot on before my 10 minute ride and is way below now.

    Could the cam timing be off by 1 tooth making the bike weak and hard to start? or would it be impossible for it to run if it was off?

    Thanks
    DuP
    #17
  18. gunnerbuck

    gunnerbuck Island Hopper

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    5,077
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    N.V.I, B.C.
    I don't like to be the bearer of bad news but from what you are describing it sounds to me like your top end is cooked... First thing would be to do a compression check in the form of a leakdown test... You will likely find compression lacking due to piston/cylinder damage... You may be able to peer through the spark plug hole with a flashlight to see any visible damage on the piston crown....

    Hopefully it's not the above and something with simple fix...
    #18
  19. Supervaca

    Supervaca Adventurer

    Joined:
    May 23, 2008
    Oddometer:
    32
    Location:
    Copenhagen, Denmark
    Well, got the top and cylinder off today, let me just warn you that the followinf images are not for the faint of heart..

    [​IMG]

    and

    [​IMG]


    that explains a lot of the problems i've been having, top ring has shattered and been spit out through the exhaust. Looks like the bottom ring and the oil ring are ok so i hope no debris has found it's way down.

    All thats left is to order neew parts and put it back together.

    Thanks for all the help

    DuP
    #19
  20. markamazing

    markamazing That didn't hurt!

    Joined:
    Jul 20, 2007
    Oddometer:
    1,052
    Location:
    Fort Collins, CO
    I bought it used off ebay for $200. and $75. for shipping. I was pretty impressed with the cost of an OEM piston, rings, wrist and clips.
    The barrel was fine and the head was beat up like yours. I intend to re-build with same head, but new piston, either wossner or proX, depends on how rich I feel at the time. I will do a complete tear down to look for additional debris/ damage.
    good luck
    #20