LC4e hiccup

Discussion in 'Thumpers' started by sss, Feb 5, 2006.

  1. sss

    sss paid to worry

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    We are off the dirt and riding down the pavement yesterday toward Cheyenne doing 70 mph. The bike is fine. It vibrates; The pirelli MT21s vibrate; the Wyoming wind vibrates; it's fine. The group occasionally accelerates to 75. Somewhere between 72 and 75, under acceleration, there is a slight hiccup, a subtle vibration or brief loss of power. The bike does not slow down but continues to miss, vibrate, hiccup. The engine does not sound different, but I can feel that something is not quite right. Back at 70-72 mph the bike runs and accelerates okay.

    Where do I start? Fuel system? My imagination?
    #1
  2. creeper

    creeper Still alive...

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    You start by posting this in the thumper forum where it's easier for folks to find it... :nod

    Anyway, a 2001 LC4E... so you should have a BST40 carb. Boulder to Cheyenne... so youÂ’re at least at 5,000 ft. elevation. You live in Boulder so the bike is jetted for the elevation... I assume. :dunno

    Done any work on the carb lately? Changed brands of fuel lately? Has the bike sat for an extended period of time?
    Is your fuel cap vent line cleanly routed without any pinches or kinks? Same question... but for the fuel line.

    When was the last time you checked your valve lash? When was the last time you checked your spark plug? Spark plug cap and wire connection... these can get loose and corrode very easily. Air filter clean?
    Check the carb to intake manifold flange for loose screws and/or clamp. Still OK?

    Remove the vacuum piston cap and check for loose screws, a damaged diaphragm, a gunked up piston and bore, a worn needle and needle jet. All OK?

    Remove the carb and read this then check your float height, needle and seat condition and while your there, check to see that your main jet is tight and not clogged.
    Any sediment in the float bowl? Pull the petcock and check the condition of the filter.

    I've run out of things off the top of my head... maybe someone else will chime in with something I've forgotten.

    Good luck,
    C
    #2
  3. sss

    sss paid to worry

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    creeper,

    Thanks for the reply. It is exactly what I was looking for.

    Is it possible to move a thread or is it better to just start a new thread in thumpers?

    I bought the bike just before Christmas. The bike started in Nevada, spent a few years in Wyoming and then moved to Colorado. The previous owner (#3) had it for two months.

    I immediately checked the oil and overfilled it [​IMG] resulting in oil in the air box. I cleaned that up and cleaned and oiled the filter. I don't see new oil in the air box drain but I will check this again.

    I pulled the spark plug. It is somewhere between tan and black (I need better light in the garage) but is not fouled.

    It will take me a little while to go through your list. I am new to wrenching and am still in the process of setting up the garage and making space.

    Thanks again.
    #3
  4. AceRph

    AceRph Affluenza Free! Administrator

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    Over you go!
    #4
  5. sss

    sss paid to worry

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    Thanks for the move.

    I gather that I need to ask the moverator to do this kind of stunt.
    #5
  6. creeper

    creeper Still alive...

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    Ace has "Johnny on the spot" relocated the threadÂ… for your shopping convenience.

    I don't know if you are aware of this SSS, but a vast resource of LC4 information that will be undoubtedly of great value to you in your quest to reach beyond n00bness is resting at the top of the Thumpers forum.

    It's called the LC4 Index.

    Hope you've enjoyed the show... remember to tip your waitresses and waiters. Goodnight.

    C
    #6
  7. ChrisC

    ChrisC Amal sex?

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    I was on the ride w/SSS on Saturday and didn't notice him lagging behind much.

    My '03 Hi-Flow is still has the OEM jetting and I can't fault the way it runs at altitude. My guess would be this LC4e has had it's main jet pushed waaay past it's OE 142.5. Maybe other BST massages, as well. I'd start by whippiing out the main jet and see where it is. Some folks really like monster mains, stoichiometry or not..... :cry
    #7
  8. creeper

    creeper Still alive...

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    Using Dr. Wrongway Crackpots "Bigger is More Gooder" air/fuel ratio theories no doubt. :nod

    Came from Nevada?... Do ya' think? Naaaa, couldn't be... maybe.
    #8
  9. ChrisC

    ChrisC Amal sex?

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    I'm thinkin'.... "my jet is bigger than your jet", or "if this 165 is good, then this 185 must be reallllly good"..... :lol3
    #9
  10. meat popsicle

    meat popsicle Ignostic

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    Main Jet!?! We don't need no stinkin' main jet! We're Federales!!!

    OK, your turn to quote a movie :lurk
    #10
  11. sss

    sss paid to worry

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    Thanks everyone.

    I have been lurking for a while. It was this forum and the vast amount of conflicting information that led me to buy the ktm. I wanted something fun to ride and with a lot of support for wrenching. This is it.:clap

    Now I will study hard and work the oil and grease into my pores; Maybe some day I will be an expert.[​IMG]
    #11
  12. laramie LC4

    laramie LC4 crash test dummy!

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    id check the emissions crap while i was at it. what you are describing sounds a lot like the vacume lock from a pinched line. check underneith the seat and see if im right...

    as for jetting. i used to ride around cheyenne all the time. depending on the mods you have done to the bike (sounds like it may be stock) i would try a 152.5 main. i was running a 160 with a 47.5 idle but i had an open airbox and a full akrapovic race exhaust.

    good luck,

    laramie :cheers:
    #12
  13. Castleman

    Castleman Guest

    Sorry to hijack the tread, try this one on Meat!

    "Its got KTM brakes and a KTM motor, its got a full tank of gas and I've got a half a pack of Cigarettes, Hit it!!! Its something close to that from the Blues Bro's. movie.
    #13
  14. sss

    sss paid to worry

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    This is an update.

    The PO had removed the ISD2 muffler and the high flow side screen and mounted the stock muffler. I mounted the ISD2 muffler and the screen and adjusted the idle to the point where it would run. I can't reach the idle mixture screw but will have the carburetor out this week and maybe can fabricate a tool for the short term. I have ordered Loaded's screw and sent the check via a slow mule so will not see that for several weeks. Any assistance or guidance regarding this short term issue is appreciated.

    I will also be working through this site to verify which vents/holes should be filtered and why that black plastic elbow is not hooked up to anything.

    The main jet is 157.5.

    When I removed the diaphragm cover I discovered black dirt/dust above the diaphragm. The area below the diaphragm appears to be clean. The slide has not been drilled. I will wait on this because it is pretty easy to get to and the mid-range response is fine for me. I may change my opinion later.

    The slide is scored on the flat side.

    The hiccup is gone.

    I think (noob's guess) that the ISD2 is set up with a racing core. I will check this later and may go to a quiet core. I don't like a loud bike but the sound of this one is growing on me. Away from the bike it does not seem too bad. I also do not want to antagonize the neighbors.

    The bike now has plenty of power; It easily accelerates from 70 mph and maxes out at 92-95 mph, but takes a few seconds to get there from 85 mph. There is some popping on deceleration and it is not consistent. Sometimes it pops and sometimes it doesn't.

    Great bike. So far it is easy to work on. I am glad to not have to remove a lot of plastic before doing anything. The gas tank is so easy to remove compared to my other bike.

    I have Flanny's Guide, Creeper's most excellent advice, a cold garage and a bike that I can ride while I enjoy wrenching this one.:D

    Steve
    #14
  15. meat popsicle

    meat popsicle Ignostic

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    They make a special screwdriver for turning that screw; not sure if you can source it locally for a quick buy. Some folks can use a stubby screwdriver to get in there. Others used a ratchet with a flathead attachment to turn it. Those you should be able to source locally.

    Creeper did a little "how-to" on those carb vents (optional upgrades I believe); it would be good reading for you. but damn it, it's not in the index yet! :bluduh

    EDIT: dug it up: http://www.advrider.com/forums/showthread.php?t=114485

    :clap but the slide is damaged? ~$35 to replace it.

    take off the end cap and look in; if you can see the midpipe (straight thru) its the racing core. the baffles insert (quiet core) is about $60 as I recall.

    The popping could be a leak in the exhaust, usually at the midpipe-can fit; common with the IDS2 since it doesn't line up well for all model years. If that is the case you can try to adjust the alignment or use something softer to fill the gaps; I have some stuff that seems to work - let me know if you need a bit.

    congrats on the fixes - sounds like you are almost there... :1drink
    #15
  16. sss

    sss paid to worry

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    I am making progress and having a great time and one or two headaches.

    Thanks Meat for the advice and for the offer of tape for the exhaust. I am not there yet and when I get to the point where I address exhaust leaks I will experiment a bit and then maybe take you up on the offer if it is still available.

    The present issue relates to the air/fuel mixture. I am about to start playing with the main jet. First, here is what I have;

    main jet: 157.5
    idling jet/pilot fuel jet: 45
    pilot air jet: 1.2

    The carburetor is clean and the float is adjusted.

    Filters are installed on the carburetor vents

    air box with snorkel in place
    screen side cover on, now off; does not seem to significantly affect the idle screw adjustment. Ultimately it will be reinstalled.
    ISD2 muffler, more quiet than a Harley so it must be the quiet core; but a quiet core is inconsistent with the past use of the bike and my hearing is not very good. I should probably pull the end off and check it some day.


    Idle screw adjustment (much easier with Loaded's screw)
    At 3 turns out the engine speed drops. At 6 turns out the engine speed barely drops. I understand this to idicate the need for a larger main jet. I will order a selection of main jets.

    What concerns me is that I am heading for a jet size used more commonly at lower elevations.

    Is there something else I should check before changing the jet size?

    If I am on the right track how high might I have to go on the main jet?

    Advice is appreciated.

    Steve
    #16
  17. potatoho

    potatoho Cheese and Rice!

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    I've got some new stuff I use for sealing flanges. Haven't tried it on the LC4 but I bet it would work great there. Worked pretty good for the two stroke flange. It's a 1" wide hi temp silicone tape which you can wrap in and around the flange (several passes) like a cast. It's $6 for 10' at Home Depot. Called "Stretch & Seal" near the plumbing.
    #17
  18. meat popsicle

    meat popsicle Ignostic

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    I have a lifetime supply of the stuff so just lemme know.

    IDS2 quite core in the Colorado Rockies (generally high altitude). Are you generally using this as a guide?

    You adjusted your float! Give us the blow-by-blow painful details :deal

    Did you do the creeptastic carb vent filters?

    If you pull off the endcap (part that holds the internal discs in place) you should immediately either see straight thru to the midpipe or the baffles blocking your view. Don't forget the high temp copper spooge when reinstalling those fasteners or you might not get them off again.

    Don't forget you might be able to pick up the main jets around town. I found them at a MC parts discounter; creeper says that most HD shops should carry them (see above link).

    I am going to let creeper give you more detailed tuning information. I use his guide but I have not tinkered enough. I'll ponder when I have more time. Hope that stuff helps!
    #18
  19. meat popsicle

    meat popsicle Ignostic

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    two-stroke exhaust runs much cooler than 4-strokes, so it might not.

    When it came time to repack my Spec2 pipes on the RD350 I called them up for the repack kits ($5 per can) and he said a $10 order wasn't worth his time and let me in on their secret:

    Owens Corning Pink! :lol3
    #19
  20. sss

    sss paid to worry

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    I have not yet figured out a few things about posing on this forum; For now I will use underlines for quotes from Meat.

    IDS2 quite core in the Colorado Rockies (generally high altitude). Are you generally using this as a guide?


    Quote:
    <TABLE cellSpacing=0 cellPadding=4 width="100%" border=0><TBODY><TR><TD class=alt2 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">Originally Posted by creepalicous
    ...
    1. Main jet.
    I believe a 152.5 main is still the stock piece. If you are at 3000 ft. elevation or less, a 160.0 main jet is a good place to start. Above that elevation, drop down a size for every 1000 feet or so.
    ...

    </TD></TR></TBODY></TABLE>
    I am using both Creeper's Guide and Flanny's Guide.

    The quote above from Creeper's Guide is what has me slightly concerned.

    Quote:
    <TABLE cellSpacing=0 cellPadding=4 width="100%" border=0><TBODY><TR><TD class=alt2 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">Originally Posted by sss
    The carburetor is clean and the float is adjusted.

    Filters are installed on the carburetor vents

    air box with snorkel in place
    screen side cover on, now off; does not seem to significantly affect the idle screw adjustment. Ultimately it will be reinstalled.
    ISD2 muffler, more quiet than a Harley so it must be the quiet core; but a quiet core is inconsistent with the past use of the bike and my hearing is not very good. I should probably pull the end off and check it some day.

    Idle screw adjustment (much easier with Loaded's screw)
    At 3 turns out the engine speed drops. At 6 turns out the engine speed barely drops. I understand this to idicate the need for a larger main jet. I will order a selection of main jets.

    </TD></TR></TBODY></TABLE>

    You adjusted your float! Give us the blow-by-blow painful details :deal

    I lied. I just checked the float. It was okay.

    Did you do the creeptastic carb vent filters?

    I checked the price on the UNI filters, called the bank and they wanted my first born as collateral. Instead I bought some WIX fuel filters at the auto supply store and put them in. This was suggested by someone in the creeper thread. I am keeping an eye on it/them/the filters.

    If you pull off the endcap (part that holds the internal discs in place) you should immediately either see straight thru to the midpipe or the baffles blocking your view. Don't forget the high temp copper spooge when reinstalling those fasteners or you might not get them off again.

    I will try to take this apart tonight. There is an open end cap and then a metal disk about 3 to 4" back (going from a flawed memory).

    Don't forget you might be able to pick up the main jets around town. I found them at a MC parts discounter; creeper says that most HD shops should carry them (see above link).

    I am aware of this and will call around. There is a HD shop near by.

    I ride from elevation 5500 to 8000 or 9000'.

    Thanks.

    Steve
    #20