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Discussion Starter #1
Hey everyone - another short snippet regarding my recent vt700 purchase.
If anyone remembers the last post, it had everything to do with the cramped seating position for someone who is both tall (me) and fat (very me). On the advice I received, I've ordered a spare seat with a good pan so I can try making something without or with much less of the butt-stopper, which just causes me to sit in a way that kills my lower back.

Moving on to today's topic - part-throttle stumble under say, 3 to 3.5k RPM.

The bike starts instantly on choke (like no kidding, instant) and idles off choke within say, 20 seconds or so. It'll even start cold (~45 degree days in Chicago) on half choke without any drama.

The only ridability problem I have with the bike, as far as engine performance is a total bog/lack of power at low RPM. Not just the fact that these engines don't produce much power low down, but that it'll fall on its face if you try to roll on the throttle too much, like it's starving. It'll buck and jump and then, once it gets over 3500 RPM, the thing will take off like a stabbed rat.

I'm assuming I've got some kind of fueling issue - maybe clogged slow jets or something - but carbs aren't really my realm of expertise. I did clean the carbs of my VT750ACE when I owned it, and they were an utter nightmare to get in and out of the bike. I probably also did what would be considered a terrible job of cleaning them having not tried before. Any advice would be highly appreciated.

Oh, is the choke on these bikes an actual choke, or an enrichener valve, like my GL1200? I ask because I assumed there was a fuel issue (not enough fuel) when I encounter the stumble, so I gave it some choke and it quickly wanted to die. On the goldwing, if I give it a little bit of "choke" it'll perk up with the added fuel from the enrichment.

As always, look forward to your replies. Thanks for the time.
-Kelly
 

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1983 Honda vt750 Shadow
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The choke is an "enricher"valve.
A true choke shuts down the air supply by a butterfly plate on the intake of the carb.
What color are you spark plugs? They are you mixture feedback.
If the caps are already drilled out for the mixture screws try to turn them out 1 turn and check it. Then out or in to see if that is a help. Check for vacuum leaks at the boots with carb spray also.
 

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1983 Honda vt750 Shadow
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Not bad color at least, but the rear plugs are a little damp, even though it looks like they have been firing, so they are not fouled. Maybe a little richer on that cylinder?
 

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Discussion Starter #5
Which carb is the rear? I'll admit to fiddling with the mixture screw on that side while it was running, setting it in and then back out to 3-4 turns just to see what difference it made.
 

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1983 Honda vt750 Shadow
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The left carb feeds the rear cylinder.
Screw both adjust screws in GENTLY till they seat and back then off 2 turns as a start and go back and forth from side to side to get the fastest smoothest idle. Then adjust the speed.
 

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Discussion Starter #7
Of COURSE the airbox is in the way of a straight shot to the left-side screw. Getting that thing back on is a pain, at least compared with the newer Shadows.

The bike idles fine once lightly warmed on both screws set to 2, but it's a bit...lopey? It's slow. Around 3 to 3.5 seems to bring the idle up to 1100 or so and it seems happiest.

The stumble is still present on anything less than light tip-in. Since I was already playing around, I even tried running the screws out 4, 4 and a half, 5 times and the issue remains.

You can also tell it's been cold here, as I have some obvious condensate in the exhaust. A small puddle dripped from both mufflers. My own fault for not running it fully hot long enough to get rid of it.
 

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Discussion Starter #8
On the plus side, my spare seat showed up already. Now I've got to figure out how the heck to cut this thing down in a way that gets rid of the backbreaker.
 
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