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Thread: Looking for ideas and solutions. Please help if you had similar problems.

  1. #21
    Senior Member RaZed1's Avatar
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    A hanging idle (eventually falling down into a weak/rough idle) is a classic sign of a vacuum leak. With the engine running, spray some carb cleaner or wave an unlit torch around the intake area. If the engine speeds up, there you go.

    Engines only draw in air. The throttle is an air control, not fuel. Fuel intake is a by-product of airflow through the carburetor. If there's a leak between the throttle blade and the intake valve, extra air will be drawn into the system by engine vacuum. When you close the throttle, the spike in engine vacuum sucks air in and allows it to continue to run fast.

    It's almost always a cracked carb boot or bad gasket at the intake flange. When you're talking about bikes old enough to buy a beer, this is not an uncommon issue.
    Last edited by RaZed1; 05-10-2019 at 03:40 PM.
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  2. #22
    Junior Member GNolan's Avatar
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    Gary and Others,

    I checked out all feedback I received from you Guys. I dissected my carb once again. I put a shim under the needle. The spring was there and correctly installed. I also opened up the Pilot jet 3-4 thousandths of an inch. I did not change the Main jet. Setting the Pilot screw (Idle Mixture Screw) at 2.5 turns. Also replaced the diaphragm (Coasting Enricher) parts but I think they were ok to begin with. In summary the only change from original is the Needle shim, Pilot Jet and Pilot Screw setting. The carb is ready to test. Uni filter will be installed before I test.

    The only open question is: Is the intake boot sealed?

    As for the "hung idle", I think the hung idle is caused by the coasting enrichment and by design. My conclusion from reading other posts.

    I should know pretty soon what the outcome is. Thanks to all.

    GNolan

  3. #23
    Senior Member RaZed1's Avatar
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    The coast enrichener will not cause a hanging idle unless it's defective/leaking air. Possible, but not likely. When they get stuck or fail, they fail shut (and they're not essential to run, in fact the bike mostly runs fine without them). They just reduce engine braking a little/ smooth out on/off throttle transitions and to a small degree help with emissions. It takes very high vacuum to open, only with higher RPM and closed throttle. It is not (or should not) be active at idle.

    The idle should promptly return to 12-1300 rpm or so when the throttle is released. Are you sure the cables are not sticking and the throttle blade is indeed fully closing when the throttle is released? you should hear an audible "click" of the throttle cam snapping against it's stop when releasing the gas.

    My money is still on an intake boot leak.

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  5. #24
    Senior Member admiral's Avatar
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    Quote Originally Posted by GNolan View Post
    Gary and Others,

    I checked out all feedback I received from you Guys. I dissected my carb once again. I put a shim under the needle. The spring was there and correctly installed. I also opened up the Pilot jet 3-4 thousandths of an inch. I did not change the Main jet. Setting the Pilot screw (Idle Mixture Screw) at 2.5 turns. Also replaced the diaphragm (Coasting Enricher) parts but I think they were ok to begin with. In summary the only change from original is the Needle shim, Pilot Jet and Pilot Screw setting. The carb is ready to test. Uni filter will be installed before I test.

    The only open question is: Is the intake boot sealed?

    As for the "hung idle", I think the hung idle is caused by the coasting enrichment and by design. My conclusion from reading other posts.

    I should know pretty soon what the outcome is. Thanks to all.

    GNolan
    What do you mean with this sentence? I also opened up the Pilot jet 3-4 thousandths of an inch.

    It was my understanding that the Pilot Jet and Main Jets should be fully seated and not backed out. Changing Pilot Jet sizes I understand but not "opened up" or at least I don't understand the statement. My thinking if the pilot jet is not seated it can "unscrew" itself even more with engine vibrations.
    Hidden Content A ride in the woods helps me relax and release tension. The fact I'm dragging a body should be entirely irrelevant?

  6. #25
    Junior Member GNolan's Avatar
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    Hello RaZed1
    I have a 96 TW with the original TK Carb that uses a round slide. If you rev the engine quickly, the rpms do not settle back to normal idle quickly. This is due to coasting enricher I believe. It is a noticeable delay but I believe this characteristic is as designed. For emissions and/or lean back fire.
    Admiral,
    I opened up the orfice in the Pilot Jet. The stock OEM jet was about 0.0135" dia. I opened it up to about 0.018" dia. The jets are well seated.

    So this evening I put everything back together. It started easy with the choke. I threw off the choke quickly and it just sat there and idled. I played with the throttle stop and the mixture screw very little. It may have started without the choke. Over 70 degrees here today. Then I took it on the road and ran it hard. It runs like a champ. Can not be any issues with the intake boot. It was a "BINGO"!

    Allot of work and a learning curve but rewarding none the less.

  7. #26
    Junior Member GNolan's Avatar
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    Hello RaZed1
    I have a 96 TW with the original TK Carb that uses a round slide. If you rev the engine quickly, the rpms do not settle back to normal idle quiackly. This is due to coasting enricher I believe. It is a noticeable delay but I believe this characteristic is as designed. For emissions and/or lean back fire.
    Admiral,
    I opened up the orfice in the Pilot Jet. The stock OEM jet was about 0.0135" dia. I opened it up to about 0.018" dia. The jets are well seated.

    So this evening I put everything back together. It started easy with the choke. I threw off the choke quickly and it just sat there and idled. I played with the throttle stop and the mixture screw very little. It may have started without the choke. Over 70 degrees here today. Then I took it on the road and ran it hard. It runs like a champ. Can not be any issues with the intake boot. It was a "BINGO"!

    Allot of work and a learning curve but rewarding none the less.
    admiral likes this.

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