1987 Honda Vt700c Shadow Only idles if choke is full. - Honda Shadow Forums : Shadow Motorcycle Forum

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Old 06-20-2010, 10:19 AM   #1 (permalink)
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Default 1987 Honda Vt700c Shadow Only idles if choke is full.

Hello to all. I purchased a shadow 4 days ago. It ran great for about 30 miles I went to slow down and the bike started to stall out as I down shifted. It quit running.. Tank was full of gas.. I left sit for about a hour it then started but I had to keep revs up or engine would start to stall out.
I made it home but it stalled in driveway.
I thought maybe bad gas.. drained both tanks removed fuel filter
blew it out. checked wireing to igniter cleaned all connectors with contact cleaner. Replaced all 4 plugs. looked good.
Checked battery voltage.. 12.85 v . charged to 13.3 v.
Now bike will start but has to have half choke to even idle.. when I give throttle it will stall.. but bike will sit and idle half choked..
If lucky I can get a Hi rev and it will stay at 3000 with choke but
and doesnt miss fire..
Im not sure if its a carb problem or a Electrical problem. Any suggestions appreciated! Frustrated John
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Old 06-20-2010, 10:40 AM   #2 (permalink)
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Default Re: 1987 Honda Vt700c Shadow Only idles if choke is full.

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Originally Posted by pcnut45840
Im not sure if its a carb problem or a Electrical problem.
No doubt it's a fuel delivery problem.
First, drain the float bowls.
Then put a healthy dose of carb cleaner into the gas.
Run it long enough to get the engine hot and cleaner into the bowls (draining them a second time will speed that up some).
Then let it sit overnight and pray.

The fact that the problem appeared so suddenly probably means there is a bit of solid matter plugging your low speed jet(s) and may require a manual carb cleaning......but try the easy route first. A new fuel filter would certainly be in order.
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Old 06-20-2010, 01:35 PM   #3 (permalink)
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By any chance, did the previous owner line the gas tank? If they etched and lined the gas tank and did it improperly, some of the liner could be coming off and clogging up the works, especially that tiny opening in the low speed jet.

You can tell quickly by shining a flashlight into the tank, if it's bare metal or slightly rusty, no liner, but if it's cream colored, metallic silver, black or any other noticeably non-bare metal color it's probably been lined.
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Old 06-20-2010, 05:10 PM   #4 (permalink)
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Default 1987 Vt700c Shadow thanks for helpfull info

I checked inside of tank and dont think its been relined.
Does anyone have a good link to download a pdf file for My 1987
Shadow VT700c.. I will checkout carbs next.. It could be a plugged idle jet.. It seems to be a idle problem..
I used a voltage probe near sparkplugs.. and found that I am not get
a pulse on front left side cylinder plug. while idleing..
Both right side plugs fire good.. and left rear is a little week.
Im leaning toward replaceing ignition coil on left side.....
Maybe its breaking down?
Can the pulse pack be a issue maybe not getting enough current to
the coil? Anyone had these issues before..?
What is the indication of a weak fuel pump..? The engine in a high rev around 3000 rpm doesnt seem starved.. only starving at idle.
Any more ideas appreciated! Thanks!!
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Old 06-20-2010, 05:36 PM   #5 (permalink)
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Default Re: 1987 Vt700c Shadow thanks for helpfull info

Quote:
Originally Posted by pcnut45840
I checked inside of tank and dont think its been relined.
Does anyone have a good link to download a pdf file for My 1987
Shadow VT700c.. I will checkout carbs next.. It could be a plugged idle jet.. It seems to be a idle problem..
I used a voltage probe near sparkplugs.. and found that I am not get
a pulse on front left side cylinder plug. while idleing..
Both right side plugs fire good.. and left rear is a little week.
Im leaning toward replaceing ignition coil on left side.....
Maybe its breaking down?
Can the pulse pack be a issue maybe not getting enough current to
the coil? Anyone had these issues before..?
What is the indication of a weak fuel pump..? The engine in a high rev around 3000 rpm doesnt seem starved.. only starving at idle.
Any more ideas appreciated! Thanks!!
Get a Service Manual. There, you will find troubleshooting steps detailing fuel pump operation, fuel pressure, voltage and etc.
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Old 06-21-2010, 12:40 AM   #6 (permalink)
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More likely you've got a bad plug wire or boot, when coils go they normally affect both plugs. 7mm plug wire is pretty easy to find, someone here can tell you exactly the type to get, and new boots are available from NGK at most bike shops or dealerships for around $10 including rubber caps.

I think your main problem is the carbs, a good cleaning will probably cure most of the problem, and fixing that spark plug problem will most likely fix the rest.

There's a resistance test for the plug wires, but I couldn't tell you for sure on that bike. You might check www.repairmanualclub.com for the manual, I know they have one for the '83-85. Otherwise, Ebay is your friend.

When it's the CDI box, pulse generator, or coil, 99% of the time it affects BOTH plugs, so it's a pretty good chance those are fine.
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Old 06-21-2010, 07:49 AM   #7 (permalink)
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FYI, your bike has two fuel tanks, connecting in series. Anything you put in the fuel tank will take about 100 miles of riding to make it into the carbs. if you want to add a fuel system cleaner, you have to add it directly to the carbs or it won't do anything.

I high idle of 3,000 RPM is easy to get on an engine that's not doing any work. A fuel-starved engine will still wind up to 3,000 RPM if it's just sitting there spinning.

Your carbs sound like they are either plugged up, or the vacuum slides are stuck. If the bike's carbs are in poor enough condition that you can't ride it, I would forego the addition of a fuel system cleaner, and remove the carbs and clean them.

--Justin
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Old 06-21-2010, 08:03 AM   #8 (permalink)
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Default Thanks for advice Found My Stator is shorted to ground

Thanks for help
I did a volt check out of stator windings.. only had about 4 volts out between any pair of yellows with it disconnected from rectifier .. while idleing.
Did a ohm check with a digital meter about .7ohm between the three
yellow leads then read to ground! Found any of the three to ground reading 1 ohm or less.. not good from what Post I read.
I found that a 1989 1100 shadow stator could be substituted according to Ricks cross references part 21-104 stator .. Presently searching ebay for a good priced used one.
My theory is.. with the stator bad the electronics is not capable of putting out enough current when I rev engine to get the coils fireing properly..
I removed both sparkplug wires on right side and engine still ran..
about same.. I used a fluke voltprobe to touch near sparkwires.
With all 4 plugs connected the right side has a strong pulse and left
doesnt flash at all.
So will start on a hunt today for a descent priced stator and gasket.. Soaked screws on cover over night have a couple stubborn ones
up by shifter.. thanks for advice!!
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Old 06-21-2010, 09:29 AM   #9 (permalink)
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Default Re: Thanks for advice Found My Stator is shorted to ground

Quote:
Originally Posted by pcnut45840
My theory is.. with the stator bad the electronics is not capable of putting out enough current when I rev engine to get the coils fireing properly..


I removed both sparkplug wires on right side and engine still ran..
about same.. I used a fluke voltprobe to touch near sparkwires.
With all 4 plugs connected the right side has a strong pulse and left
doesnt flash at all.
Sounds like you are progressing good. A couple of comments:

If the battery is fully charged, it doesn't NEED anything from the stator to keep the bike running proplerly.....unless you have a LOT of lights or something else causing a high drain.

If your idle speed is low, 4 V across the yellow wires might be normal. You need to pick up the engine speed a bit and see what you get.
This is a moot point, however; if the stator really is grounded, it needs to be replaced anyway.

Your last spark test is, I think, misleading. If you can kill the right side altogether and it still runs.......that means that the left side spark must be pretty good. Your probe might be "seeing" a pulse on the right because the circuit loop is somehow bad on that side; bad plug, wire or boot.......and the voltage is leaking OUT.
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Old 06-21-2010, 11:02 AM   #10 (permalink)
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My bike is the 1986 model of your 1987. They are identical.

At idle (1,100 RPM, as indicated on the tach), I get 18 volts between a pair of yellow wires on the stator. 4 volts is way too low.

Having anything read between a yellow wire and ground is a dead give-away for a bad stator. Looks like you sure need a new one.

As ER2 already said, I think you're chasing a red herring with your last spark test.

Not too surprising that the 1100 stator will for your 700. Honda uses many of the same parts across that era of bikes.

--Justin
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