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Discussion Starter · #1 · (Edited)
Hello to all you motorcycle gurus,
Friends call me Steve, I recently bought a 85 shadow vt500c, the bike is in really good shape for being 25 years old, only a few dings. I believe it to be bone stock, and the tags on it expired 9 months ago so i also think it was riden regularly. The issue I'm having is that while is starts just fine the throttle is slow to respond and once I feather it up to about 5k it will only hold it for a few seconds before dropping drastically. So I started looking around to see if there was anything obviously wrong, and found only one thing, the air box is missing the connection to the right side carb, that's to say that the plastic plumbing that is suppose to go to the carb is gone, the other side is there. So any thought anyone might have would be great. And how vital is that air box tube?

P.S. Here's a pic of the bike after I painted the tank.

 

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don't know on that specific bike, but the missing airbox tube will probably cause really bad running. The carbs are designed to work with a certain amount of vaccuum cause by the air filter/air box.
Also make sure your fuel pitcock is in the ON position.
 

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you definatly need that tube it will make a huge difference. is that gas cap vented? your original cap was the only vent for the fuel tank. your picture shows the powerchamber and mufflers are missing from the exhaust. open pipes would result in the bike running quite lean and hot. just because someone else was rideing it does not mean it is in good shape. get the manual eather download the one here or buy the clymer manual. check and change all the fluids, all 4 sparkplugs, check the age of the tires, check the battery.
 

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Discussion Starter · #4 ·
Tires, plugs, and fluid are all new. Thanks for the info about airbox, I guess I'll start looking for one, oh and that's not a gas cap, it took me a minute to figure it out but it's the cap from the spray can I used to paint the tank. The tank cap is also missing and the paint cap was used to keep paint outta the tank during painting, and didn't get removed till the next day after it was dry!
 

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Missing gas cap and airbox seals may be a big part of you issue. Both are hurting the vacuum in the carbs. It can be a tuning nightmare, but you could eliminate the airbox and go to individual filters at the carbs. IF you can find the boots you might be able to make some out of rubber hose.
 

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Discussion Starter · #7 ·
Ok so I found an orig airbox, got it for free off a guy that owns about 35 bikes, most are down to the frame but he found one, so that should help a bit. No luck on a cap yet though.
 

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Discussion Starter · #8 ·
Ok so I dumped my tank (had some really pretty crud in it), replaced fuel filter, added a complete airbox, and ran some seafoam through the fuel line and within 15 mins of running, it sounds like a bike again!! Now for tags and a test ride!!! :)
 

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sounds great!
 

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Steve: One thing you will probably find with these bikes is that they are pretty sensitive.... meaning one broken piece can really make a difference in how the bike performs... not like an old chevy small block that would keep running even after half the parts had fallen off.
 
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