HELP ONLY RUNS GOOD WITH SOCK PLUGGING AIR BOX?

Everything in-between the gas cap and the carbs. Also how the engine inhales.
BILLZBIKES
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I ride: 2000 Vulcan 500 LTD, 1991 H.D. Sporty 1200, here this is easier http://bikepics.com/members/billz67/

HELP ONLY RUNS GOOD WITH SOCK PLUGGING AIR BOX?

Postby BILLZBIKES » Fri Apr 19, 2013 11:38 am

I've worked on many many many bikes, mostly dirt bikes but i have worked on more then my share of street bikes too.
Now this is making me scratch my head. My sister let her 2000 Vulcan 500 sit for a few years (2 or 3) well for her birthday i told her i would get it running agian. ok i figured normal work from a bike that had sat, clean the carb, drain and clean the tank. Ok this is a valcan clean the exaust valves. I do all that and it runs kind of on only 1 cyclinder. I test both pipes with a lazor heat gun and i see that both cyclinders are working as the temp is like 150 and the other side is like 260.. hum, I clean the carbs once twice three times. ok four times!!! and it still runs like that. I change the plugs and nothing changes, it idels perfectly no choke to start just hit the button and she's ideling great give it gas and it falls on her face. I pull the carbs and check the bladder on the slides and they look great. No holes or rips. got it back together and still no change. I have it running and place my hand over the opening on the top of the air box and give it gass and IT RUNS PERFECTLY... I think of maybe it needs to be placed together for it to run right so i put it all back together and nope that problem came back. I place a sock on the top of the opening of the air box and put the seat on the bike and it runs perfectly, take it out and ride it for 5 minutes and it's perfect. Can someome tell me what i am missing?
Please help

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Triangles
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Re: HELP ONLY RUNS GOOD WITH SOCK PLUGGING AIR BOX?

Postby Triangles » Sun Apr 21, 2013 7:10 pm

You might need to take the carbs off and completely apart and do a professional cleaning. What you describe sounds like small passages in the carb are plugged with varnish. To my knowledge the only way to dissolve them is to soak the disassembled carb in some nasty solvents for a few days if not longer. If it starts with no choke your idle circuit is WAY rich. The 500's engines are fairly cold blooded. It is typical for mid throttle to fall flat when the bike has been sitting for more than a month or two. Ie it may idle fine but practically stalls then pulls hard when you roll on the throttle. If its not too bad you can usually cure it by running a tank of gas with concentrated carb cleaner thru the bike and there should be a noticeable improvement but the flat spot wont completely go away until running about 3-5 more tanks of gas thru the engine. The fact that you have to restrict air intake with a sock shows that you have a lean condition as the restricted air provides more vacuum to pull more gas into the engine. This provides further evidence your carbs are really gummed up. The main jet and slides are not the problem, there are smaller passages for part throttle that I don't believe it is possible to manually clean other than with strong solvents I mentioned above. Additionally once you've got the carbs mostly working you need to use a manometer to balance the carbs. Otherwise you may potentially have one cylinder doing most of the work. While you've got the carbs off you can get the balance fairly close by visually adjusting it so both butterfly valves close at the same time.

IMHO I would try what I mentioned above with the concentrated carb cleaner in the gas and running a few tanks thru her. If that doesn't cure it then the passages are likely plugged and you will need to soak the carbs to dissolve the varnish. Once you've taken care of the mid throttle stumbling you really should properly adjust the idle. The start with no choke tells me your idle circuit is WAY rich. A cold engine needs the choke to start. But will start fine with no choke once it's warmed up. Finally once you've got the idle and mid throttle issues taken care of, using a manometer to balance the carbs will make the engine run at its optimum. I rattled this off half awake, hopefully I is coherent :)
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