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Discussion Starter · #1 ·
Continuing from my other thread (https://www.hondashadow.net/forum/55-wanted-board/566328-part-needed-red-label-cdi-box.html). I've been updating it for a while, but I felt it was time to make a new thread.



I've been working on getting my 84 Shadow vt700 running for some time. It now has spark, compression and fuel, but doesn't want to start, just backfires every now and then as it turns over. I pulled the plugs and found gas on them, so I'm thinking it's an air delivery issue.


Checked the carb out and the vacuum pistons are able to open just fine by hand, but are VERY sticky coming down. I also noticed the needle jet seems to be loose in its seat in one of the pistons. Could this be my problem?
 

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Is there any way the spark wires or coils are wired to the wrong cylinder? They need to be dedicated to the cylinder that is fired by the pulse generator in sequence of timing.


Also the slide should drop easily with the spring pressure. I would compare each carb to see why they drag. The looseness is weird also. One guy had his apart and left a small brass piece out where the needle goes into the lower chamber.
 

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Discussion Starter · #3 ·
Is there any way the spark wires or coils are wired to the wrong cylinder? They need to be dedicated to the cylinder that is fired by the pulse generator in sequence of timing.


Also the slide should drop easily with the spring pressure. I would compare each carb to see why they drag. The looseness is weird also. One guy had his apart and left a small brass piece out where the needle goes into the lower chamber.

It's possible I swapped the connectors when I was testing the cdi boxes, will check that out later tonight.


Something I was wondering though...Does it matter which coil terminal the wires from the cdi boxes connect to? I couldn't find any markings on the ignition coils, and couldn't tell by the picture in the shop manual so I just connected the wires however they seemed happiest placement-wise.


The pistons were covered in dust and dirt from the PO leaving the carb out, so I figured it was dragging due to a buildup of grit. Pulled them out and cleaned them as best I could, but they still drag which is why I came here. Didn't see anything like a loose piece when I checked it out, but I'll check again.
 

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It doesn't seem to makes a difference which connector is the power in black/white wires. Mine don't have + or - markings either. I think that is because these are a complete circuit with the 2 plugs firing forward and reverse and it wouldn't matter which way the current flowed. Basically a transformer.
On the older cars with a single coil if you wired it backward it would produce about 30% less spark. But they were wired different inside.
 

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Here is a wild idea. The 1984 has 3rd box called spark unit # 2. Some guys have said that if they take that out of the circuit it starts and runs.

It's CRAZY because my 1983 manual shows I don't have one of those and yet mine does have one sitting behind the starter area and plugs in-line into the 2 main boxes,.

It is one of those factory secrets the Japanese don't tell about. Try to remove it to see if that helps. It just disconnects.
 

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I forgot the picture of the wiring.
 

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Great news!!!
Did you remove that 3rd spark unit and it fired up?
Was that the fix?
 
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