Question about 1985 Honda VT 500 C Shadow

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1986 honda shadow vt500c throttle hesitation.

Hello I have a 1986 honda shadow vt500c I am nearly at my wits end with this thing. as long as I baby the throttle it's fine but while in neutral if you crank the throttle with any force theres a hesitation and then a dramatic pick up. if you go quickly from none to full throttle it bogs and turns off. carb mounts seem to be good as I sprayed them with electrical contact cleaner and there was no rpm increase. could leaks in the airbox cause this?

Posted by cindi0418 on

  • 2 more comments 
  • cindi0418 Apr 30, 2009

    So you wouldn't think this could be caused by an air leak?

  • cindi0418 Apr 30, 2009

    if the sliders on the carbs are the things you can see if you look down into the intake when the extension that leads from the air box to the tops of the carbs is removed (they look like little drums that the needle runs into the center of) they don't move at all if you turn the throttle with the engine off.

  • cindi0418 May 01, 2009

    does the carb have to be dis-assembled to move the clip?

  • cindi0418 May 20, 2009

    Leaky intake mount. Thanks though.



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If your bike has carbs and not fuel injection, ( difficult to remember back 23 years ago ), then remove the carb slides and move the clip on the jet needle down one notch. This will richen the low end mix and provide it sooner. You may need to go two notches but start with one notch. Also, sync the carbs such that the slides on both carbs move at the same exact instant when the throttle is slowly turned from idle speed < engine off. Clean the carbs when you get a chance.

Please rate this solution. Thanks Cindi!

Posted on Apr 30, 2009

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  • tombones Apr 30, 2009

    Doubtful that it is an air leak. If the slides don't move without the motor running, that means you have CV carbs. You can still move the jet needle clips. Moving the clips is an easy thing to do and they can always be moved back if desired. Give it a try.

  • tombones May 01, 2009

    Forget it. I have to keep reminding myself that this is a CV carb. You have a jet needle but there is no clip on the needle. Pardon my French, I hate CV carbs. The standard adjustments arn't there.

    As you suggested, an air leak is possible. A carb diaphragm with a pin hole in it? Most anything can happen with CV carbs. At this point I would suggest that you get a factory service manual for your specific bike. There will be a troubleshooting section at the back and a carb disassembly / reassembly section in the middle. A good source for a service manual is to Google " service manuals honda ", or try your local library. Often guys will donate manuals to the library. Also available is

    I have answered 877 questions since March 11th. I have a 95% rating. CV carbs are one of the few things I have problems with in motorcycle repair. I would still tell you the carbs need to be cleaned, but CV carbs are somewhat delicate and are best serviced by someone who is familiar with them. Google " vintage honda parts " and you should be able to find carb diaphragms if that is what you find is needed.

    Start making some phone calls. Your bike is 23 years old. Most dealers will not work on a bike that is more than 10 years old. Often the service guys will do the older bikes as a sideline in their garage at home. Don't ask the dealer, ask someone in the service department. Ask if they work on older bikes, and if they don't, who does work on older bikes.

    Don't necessarily call just Honda dealers. Mechanics can jump from one brand to another. The top mechanic at "Yamaha City" may have been a Honda mechanic several years ago. Enough phone calls and you should be able to find someone.

  • Justotter63 Mar 19, 2012

    I c this is 3 yrs old, but am having same problem. Paid 4 a new carb kit, total redo, git the short end of course. I need the spark plug gap for it.



Paul Marsh

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I had a similar issue with my 85, I hope this helps , first do you have excess oil in the bottom of your airbox , mine did and it runed the air filter , are you draining the blow off tank ? I put in a new airfilter and used a tin of carb clean to clean out the carbs , when the bike is running crankcase blow off from the botton of the airbox blow excess oil up in the intake .. I cut a piece of plasitc about 2 in square and bent one end at at 45% and expoxed into the airbox SO THAT THE OIL WITH NOT HIT THE AIRFILTER DO NOT SEAL OFF THE HOLE . while you are cleaning the carbs with the cleaner open the choke a bit to clean the choke jets a bit as well , also check a plug from each cylinder are they black and sooty , this would be an indication of two rich as a result of bad airflow casued by pluggged airfilter ....

Posted on May 07, 2009

  • Justotter63 Mar 19, 2012

    I thank u much. I paid to have all tbhis done, new carb kit, oil change, fllters, oil



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Jul 27, 2009 | 1986 Honda VT 500 C Shadow

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