Trying to smooth out the rough spots
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  1. #1
    Senior Member mhomadness's Avatar
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    I’m stumped. Trying to smooth out the rough spots on my 97 TW.



    The symptoms:



    The engine has an intermittent surge, almost like a very brief cut-out. It is most noticeable at low RPMs, but is always there to some degree no matter what the RPM or throttle position is.



    Background on the bike:



    I bought it from original owner, California bike, had 888 miles on it when I purchased it. It has just over 1000 miles on it now. It had most of the normal issues from sitting too long, but was in otherwise good shape, never abused (except for sitting) never wrecked, no modifications at all, and all paperwork was with the bike including a service slip from its 600 mile service.



    What I’ve tried to solve problem:



    Gas tank was clean inside, no rust, but I replaced the fuel valve anyway. Cheap insurance.



    Carburetor was in poor shape, opted to replace with new carb. Increased main jet size, adjusted float, (new, yet was out of spec) pulled cap & turned low end screw out to 3 turns. Checked the carb intake joint for air leaks, passed. New air filter. Did not shim needle.



    Adjusted valves & cam chain.



    Replaced the stator assembly & pulser coil. Turns out I did not need to do this, fooled by f’d-up multi-meter. (Oh well…) New spark plug of course. New spark plug boot.

    Tested ignition coil with proper working meter, all OK.



    Bypassed safety switches, problem still there.



    Used my friends excellent spark tester. He works on Echo brand equipment, and the tester fit just right. Nice viewing window to watch spark, & that’s when I noticed a strange thing. The spark would behave slightly erratic when the cutting out symptom occurred. The spark would momentarily appear weaker, with a bright spot of spark appearing at one end of the testers electrodes. “?”



    My suspicions are either the bike is still a bit too lean, or could this be a CDI problem?



    I pulled the plug after running it for aprox. 2 hours, & its too clean! Definitely not running rich, no soot, no black smoke from the exhaust. I did some slow speed tests with the choke pulled out just a little, and this made it run & ride much better & smoother.



    So now I have pulled the carb off again, & it’s sitting on the bench waiting for attention.

    Since it seems like a lean running condition, what would be a good next step? If I should shim the needle, I could really use some guidance as to the correct way to do this, the manual is seriously lacking in detail as far as removing the slide / needle. A link would be great. All other ideas welcome. Miles on motor at this time is 1020. m.

  2. #2
    Banned qwerty's Avatar
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    Spark tester indicates bad spark during intermittant crappy running and you pull the carb to fix it?

  3. #3
    Senior Member mhomadness's Avatar
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    Yeah, I did pull the carb off, but not apart, yet! As the symptoms indicated, a poor spark was observed during a stumble, however, could the strange spark be the result of the engine rpm varying momentary during a lean run condition? Just putting a toe into the cold water before I throw another pile of $$ at it, trying to correct the problem through denial and error. m.

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  5. #4
    Senior Member mhomadness's Avatar
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    So, nothing else?? Guess I'll try a few further things, & let you all know what I find. But just for fun, why don't any of you who are the gambiling type chime in with what you bet is the problem, and we'll see who is the winner of this silly game. Once I get to the bottom of this, I will most likely sell the money pit, & put whatever I can get for it twards a MUCH newer TW, as I see they can be had for what could be called cheap, and work with that. I'm tired of crap, and I like the TW well enough to want a good one.

  6. #5
    Senior Member bcscammell's Avatar
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    Quote Originally Posted by Mikes House of Madness View Post
    So, nothing else?? Guess I'll try a few further things, & let you all know what I find. But just for fun, why don't any of you who are the gambiling type chime in with what you bet is the problem, and we'll see who is the winner of this silly game. Once I get to the bottom of this, I will most likely sell the money pit, & put whatever I can get for it twards a MUCH newer TW, as I see they can be had for what could be called cheap, and work with that. I'm tired of crap, and I like the TW well enough to want a good one.
    When I bought my bike it had a surge while at cruising speeds when the throttle was held at a constant position. I put in a larger main jet, shimmed the needle approx. .050" and adjusted the the idle mixture screw until the engine responded quickly, took trial and error to get it feeling right. This solved my problem. It sounds like you have eliminated other possible causes of a lean mix and all that is left is to shim the needle. There are threads under the technical section that show exploaded views of the carb and the positioning of the shims.(TK carb photos and parts identification). Remove the throttle cables from the carb, loosen the clamps at the front and rear of the carb and roll the carb to the right side of the bike, remove the screws on top and remove the black cap. The needle pulls out and the shims are inserted between the white plastic washer and the c clip. I realize your carb is off at this time but you will probably have to repeat a number of times until you have it right. The needle varies the fuel mostly between certain RPM's but does have an effect to a lesser degree above and below this range. The bikes come lean from the factory and depending on where you live the surging may be more or less noticable. You say the enricher being pulled partially on helped a lot, this also would indicate a richer mix is required. This would be my guess. Good luck.

  7. #6
    Senior Member tw200sgp's Avatar
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    Can you borrow a CDI and try that?

  8. #7
    Senior Member mhomadness's Avatar
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    Wish I could borrow a CDI, but no chance. Going to shim the needle, as that seems like required / standard mod to all TW carbs for the most part. Also going to try a larger main jet, for kicks, & see if I can make it run rich, with this, if it still stutters with all the extra fuel available to it, I'll be more inclined to spending $$ on a new CDI. Playing with the carb is a lot less $$ at this point, and at least I can feel like I exahusted that possibility, just in case a new CDI unit does not cure my woes. A CDI going bad from years of sitting, some of you might be asking your selfs that, so here is a possible clue: The "C" in CDI stands for "Capacitor", and electrolic capacitors have a bad habit of going south with time, in use, or just sitting on the shelf. I'm not fooling myself, just trying to keep my cost down if at all possible. You know the saying, "Wish in one hand..." m.

  9. #8
    Senior Member mhomadness's Avatar
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    And now for the latest news on the Boont TW waz-za f**k saga!



    When we last joined this story I had pulled the carb & placed it on the bench in order to work with it to try and eliminate it as the culprit before I threw another pile of $$ at this money pit, i.e., a new CDI unit. They cost enough on line as it is, but I had to laugh at my local dealer when he quoted me a price of 1/10th the msrp of a new bike for a CDI unit. Balls!



    Now with the carb in my clutches I first replaced the bowl screws with alan screws, much easier to r&r. Next I took the main jet & enlarged it to my next drill bit size. I then removed the slide & shimmed the needle .040”. Reassembled the carb, & drank beer(s).



    Today I installed the carb onto the bike & tried it out. After a proper warm-up, a quick trip down our dirt road & back revealed that the bike performed extremely well at LOW rpms, but fell flat on its face the moment the throttle was cracked open at all.



    Utilizing advanced caveman-like deduction, I decided to loosen a few things, turn the carb 90 degrees, remove the bowl & replace the main jet with the stock .018 jet, & give it a try.



    Now the bike has never run so good!! It was no problem to pull a little wheelie, more power than I have felt it produce yet. That’s when friends came by, & so I put up the bike & drank beer(s).



    Next will come the shake down test. It could still be an intermittent CDI issue, or I may finally have got lucky, & can forgo a new CDI & spend the $$ on tires!



    Will keep all of you posted as to the outcome of the proper shake-down test. With improved outlook, m.

  10. #9
    Senior Member turborob's Avatar
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    For what it's worth, my bike cut out, and I bought the CDI and my bike still cuts out....



    Moral of the story? Check the cheap stuff first but you already knew that!

  11. #10
    Senior Member mhomadness's Avatar
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    You said it Turborob, & for others out there who might read this saga, in a nut shell, do all the tune-up items, pull your carb & check for dirt, crud, float level, (remember, mine was out of adj from factory, on new replacment carb!) follow the vast amount of sage wisdom on this forum, along with the shop manual, & try to piece together a list of clues that could lead you to an ultimate repair. I still have not given the bike a proper shake down ride, and have not ruled out that I could still have a prob with the CDI, so I'll keep you all posted..



    Will m's bike go good? Will Jannett admit to Bruce that she's carrying Rons baby? Tune in next time folks for another heart stopping tale from Mikes house of Madness! m.

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