Dies after start and random plug

Hey y'all, I’ve got an issue. I can’t quite wrap my head around with my 1980 xj650.

Last time I asked, a question for my bike it was grenade throttling, and I’ve come to fix that issue, and last night I even had it going at 1,500 rpm alone, not without faults, but now the issue is it's killing itself. I’ve kind of got a list of issues, so please stick around.

Alright, for my first issue, I tried vacuuming syncing the carbs, and it was in sync, but one of the gauges was going crazy. I’ll add a video, but now the next day it’s killing itself completely and won’t start without starting fluid and pulling the throttle, but the bowls have fuel, so I just don’t know.

Another issue is that I’ve got a random black wire that goes to nothing and a plug that, believe it or not, goes to nothing. I want to say that the plug is for my blinkers, considering they don’t work. I’ll add photos.

I just don’t know what to do. I know I have a vacuum leak, and I feel like it could be the throttle shaft seals.

This is my first bike, and I don’t want to give up on her, but obviously she wants to give up on me. So right now it's kinda ask for help before I go and take the carb apart again. I appreciate anyone who can give me an idea on the issues.

here’s the video:
https://youtube.com/shorts/9ZIIlTr2Tf8?si=nJln75T98-_PQk_E

 

Tip for anyone reading this, when posting vids, post longer vids and slow down the camera movements.

OK,
For the sync gauge, did it come with some little plastic valves? male fittings on both ends that you cut the hose from the gauge to the carb and then insert those little valves. Those valves are used to restrict the air flow to the gauge so that the needle does not bounce so much.

Are you certain all 4 cyclinders are firing? That can also mess with the sync.
That sound of the bike especially if its stock pipes does not sound like you are running on all 4.
If your warmed up and have the choke off, are all the pipes way too hot to touch?
Is it a YICS bike? are you using a YICS plug when syncing?

As far as the lone black wires, you got to trace where they are going to.
the 3 prong connector might be your turn signal relay? Do your turn signals work?

My personal opinion on vacuum leaks is that too many people focus on that before focusing on the more common things. Often its because its the first thing people suggest you check when the bike is not even running on 4 cyclinders, is out of sync, carbs not cleaned properly or idle screws not even adjusted right.

 

Yes, I’ve accounted for all that right now; it’s straight piped, so that’s what you're hearing. I’ve put them in sync both on the on the bench and in the vacuum. I’ve cleaned the carbs; it’s not a YCIS bike, the idle screw is good, and the black wire is not connected on either side. I just wanted to see if people had an idea. Also, yes, my blinkers don’t work, and that’s why I figured that’s what it is.

 

The wires to the coils come straight from the tci so unless power to the tci is affected by that wire it hasn't any importance in running.
The 3 pin socket is one of two that looks like(other being headlight) that and is in the right place for the indicator relay.

Spark and fuel/air are key to running. Basics.
Running well is a whole other set of pain of course.

So.
Battery -> ignition switch -> cutoff switch -> crank pickups -> Tci -> coil -> plug wires -> plugs caps -> plugs
And
Tank -> tap -> hose -> fuel filter -> carbs
And
Air filter

For the main 3 things.

Each one one those links can have issues, some more than others.

I personally had a crimped fuel line last week which was so stupid I slapped myself when I found it.