Stalling at Idle (1982 XJ650 Maxim)

So I rode to work yesterday morning (Tucson Arizona) it was about 50 degrees. I put the choke all the way open on start up and let it warm up while I got my gear together. I rode 25-30 miles at about 45ish mph stopping occasionally at lights to work. I got off at 3pm, it was a nice cool 90 degree dry heat. I started to ride home. The bike refused to maintain an idle at stop lights and died on me twice. Thinking maybe I was just an imbecile I walked it across a cross walk into a gas station and put in some more fuel (91 premium) based on my math the bike has a 3.4 gallon tank and should have roughly 30-40 mpg based on a Google search it should make it like 120 or so miles and was at 65 mile at time of stall from last fill up. 2.4 gallons went into the fuel tank so theoretically I should have a whole gallon left correct? After I let it warm up again at the pump I was able to get it home but HAD to have the choke all the way open until I was maybe 5-10 minutes from home or it sounded like it was going to die on me again as it did previously with the choke all the way open.
Am I an idiot and it was just running on empty?
Do I need to again fiddle with the idle screw that I just can't seem to wrap my head around?
Am I an idiot and not using the choke correctly?
Please tell me I'm an idiot and my bike's ok.
Are there any surefire methods to set the idle screw?

 

I should also state that the carbs have been cleaned and battery was charged last week.

 

And when was the last time the valves gaps were checked?

Also, check your coils and plug wires.

My 81 650used to to that. I found that one of my coils was going bad as well as the valves were out of spec.

 

I'm going to assume never because that's how my ownership of this bike is going. Any tips on where to begin to do that?

 

After a quick search online checking the valves looks to be way beyond my BS diy skills. Any way to diagnose to make sure that's the problem?

 

if you're opening the choke ( fuel enrichment) that could point to the carbs, fuel passages, jets blocked....float height(s) off.....?

Are you sure she's getting fuel, when NOT on 'choke' (float heights, float bowl etc)

 

Adjusting valves is easy , requires some allen wrenches, metric feeler gauges , an adjustable wrench, a JIC screw driver , and a large zip tie or piece of romex . A plug socket and ratchet to remove plugs and a thin blade screw driver or pick tool to pull shim out . The other thing for you to check do you still have the stock vacuum petcock? was it set to ON or PRI? check vacuum hose to make sure it is not split or off. Run bike on PRI see if this helps if so your petcock may need rebuilt . Xj 4ever sells overhaul kits they are cheap .

 

Petcock was set to On at the time of stuttering. I'm not sure if it's stock or not. Looks the same as the one in the specs exploded view.

 

My neighbor who is a mechanic cleaned the carb. I trust him.

 

Try it on PRI see if it runs better, but check hose to manifold .

 

Also that is a laundry list of things I don't have but will gladly purchase if they assist in fixing the problem; any idea how much that haul would cost me?

 

The hoses are very old and do have cracks but no leaks that I can tell. They are on my list of things to fix was hoping I could get some miles in before hand though.

 

Not very much if you get it from harbor freight, but the quality of the tools is not there. You can either invest in good tools, or get harbor freight quality.

 

I'm ok with Harbor Freight now to be replaced at a later date.

 

At Harbor freight probably less than 30$ Have you went to xj4evers site at top of page? go to the information overload hour lots of good info . There are some threads on doing the valve check ,after taking measurement go to chart in manual see what reading it takes ,after pulling the shim read number on bottom of shim (NEVER install with number face up ...it will wear away number) determine if it requires a different shim Example if shim is 275 and chart shows 280 , that is size you need . Most Yamaha Dealers have the shims when I did mine I needed 3 shims cost 9$ each .Sometimes you get lucky and only have to move shims around the cylinders. Just do not turn over the engine without a shim in place . It sound hard but is not bad at all should take about an hour , another tip write down what shims are in which cylinder and weather it is intake or exhaust this makes it easy the next time you have to do this.

 

Ok cool. As for the plugs and coils?

 

Ok so it happened again today. Rode to work in 50 degrees with no problem whatsoever. Halfway through my afternoon ride home it just drops RPMs and dies slowly, trying as hard as it can to rev back up but drops to 1k with the choke all the way open in desperation and then kaput, dead. After some prayers and a virgin sacrifice on the side of the road and trying to start it like mad in ON, PRI, and then RES, it comes back to life. It has 48 miles logged and I filled it up the day before yesterday and didn't ride it yesterday. It has 0 issues until like the halfway point of the trip.

 

pop open the gas cap . see if it starts up . the vent in the cap may be clogged
Your Gas Cap and You.

I would just clean the cap to be sure.

It could also be your pickup coils failing. had an issue like you discribed. I would take bike on test ride and it would fail and run on 2 cylinders at the same point in the test ride within a half mile.
last test ride pickup failed completly no restart after it cooled down for 20 min.


if it were a charging system/battery problem I doubt that you would get bike started again

if when your vac hose heats up it develops a crack or leak it would be difficult to restart bike and your carbs would be starved for fuel. consider changing that old hose cheap fix

 

Ok going to try that in a bit once it cools down I'm scorched.

Ok please stick around I will test this within the hour and report back

 

My friend believes it may just be that the idle mixture is still wrong? But I honestly have just kind of been setting that until it just stops stuttering and hoping for the best?