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BroncoII Shadow
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   Posted 8/12/2008 9:13 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I have an 84 VT700C that I just purchased.  Starts, idles, runs fine... except between about 3700RPM and 4400RPM reguardless of what gear it's in, or speed, the bike seems like it's missing.  Any other RPM range higher or lower the bike fires normally, and seems to run normally.  I seem to be getting poor fuel milage.  The plugs look to be normal, no caking oil or white ash, or anything out of the ordinary.  I ran a can of Seafoam through the fuel but nothing seemd to get better.  Choke on or off at that RPM range does nothing.  The bike seems to cruise at any gear in that range, so is there something in the ignition that would be worn out so the bike wouldn't fire in that particular RPM range but will higher or lower?  I'm out of options!
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Macmac
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   Posted 8/12/2008 10:05 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Is this bike all stock, or has it been tampered with in the exhaust and air cleaner parts?


Oil Monger

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BroncoII Shadow
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   Posted 8/12/2008 2:19 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
The bike is totally stock. I rode it today again, and fiddled with the choke some more, and a slight tug on the choke made it run better. I guess before I was pulling too much choke because it didn't seem to make a differance, but a slight bit of choke seemed to make it run smoother. Any idea with this added information? It still is between that rpm range only that it runs poorly.
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Macmac
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   Posted 8/12/2008 2:53 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
This one is a tuff deal.. This is midrange rpm. What the problem is, is you are just lean enough to have a flat spot in this rpm range. Being all stock really helps narrow things down though.

The first thing I would do is re-new any and all fuel lines and any vacuum lines. If there is a filter on the fuel line changed it.

I can't say i am familar with the bike one bit, but i have worked on enough things over a long time I am certain of what I am saying.

The 'NEW' info is very telling, and yes to do this 'test' you pull the choke ever so slightly and very easy. The choke is really a enrichment valve system, and using it manually to tell if a mix is lean or rich is very possible if you work it easy.

The problem is finding out why you are lean in mid range.

It might be a bad fuel line sucking air by a fitting. It might be a bad vacuum line to the petcocks sucking air most likey at the hot engine connection.

It might be there is a internal passage in the carb body(s)? because this just might be close enough in that low rpm jetting still shares with mid range jetting.

But above this rmp range things are good huh?

What happens if you sneak up on this rpm, riding easy thru it and past it all real easy like?

I expect you are throttling up like you really mean it, which is pretty normal, but the test is like you just ran into ice on the road in a storm and you want outta there, but nice n' easy...

I am wondering if this will be more or less with in reason normal?

Next would be to really romp on it, and see if the bike really has a deep flat spot, and it might buck, gag and take off like a demon.

There are other things you can do as well, but first these lines must be a known good.

Probably Richard will be along, and he may be familar with the bike. A newer poster triumph guy is pretty good as well.

You might read the sticky post on Vac Leaks, just the first post. When I wrote it I didn't expect anyone to reply to it.

Never the less the first post is pretty long.


Oil Monger

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shadow rider35
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   Posted 12/3/2011 7:36 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I have a problem with the choke not opening all the way on my 84 honda vt700c. if i am looking at it right it looks to be vaccum operated
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shadow rider35
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   Posted 12/3/2011 7:40 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I dont know if i push them back up so I can ride it if they will stay up or come back down and closed. the guy i got it from said he never used the choke at all as long as he rode it everyday
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Easy Rider 2
Central Illinois / Central Florida

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   Posted 12/3/2011 5:14 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
shadow rider35 said...
I have a problem with the choke not opening all the way on my 84 honda vt700c. if i am looking at it right it looks to be vaccum operated
I think you might be looking at things backwards.
 
I don't remember ever seeing a vacuum operated choke.......unless you count that little plastic flap on cheap lawn mowers.


'06 Suzuki S50 (VS800)
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shadow rider35
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   Posted 12/4/2011 7:05 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
well the choke cable has two metal ends that screw onto each side of the carb but does not hook just blocks a hole, its hard to explain really but the choke plungers are only half way open
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Easy Rider 2
Central Illinois / Central Florida

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   Posted 12/4/2011 8:55 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
shadow rider35 said...
well the choke cable has two metal ends that screw onto each side of the carb but does not hook just blocks a hole, its hard to explain really but the choke plungers are only half way open
Trust me, those cable ends DO something inside the carb that controls the plunger position.
 
It is not unusual for the plungers/slides to become sticky due to fuel residue.
Some spray carb cleaner and a little manual manupulation might free then right up.
 
 


'06 Suzuki S50 (VS800)
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shadow rider35
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   Posted 12/5/2011 5:42 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I moved the choke lever but it does not seem to move on the carb side and the bike wont start with out the choke, i do have a book but its not very clear
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