Another Won't start thread XJ 500

I'm not gonna lie, I'm always hesitant to post on here. It's just intimidating and I feel like an idiot for being new, and not knowing so many terms or basic things. Just thought I'd preface with that. Been working on my '81 XJ 500 quite a bit. I'll try to just be short and quick. Started when I bought it, but only with spray, and ran pretty rough. Took the carbs off, cleaned them, they didn't seem too dirty actually, used an air compressor and carb cleaner. The membranes had a couple tiny holes, at the time didn't think it was too big of a deal. Worked on the bike more, put on pod filters, yes I know how this forum feels about them. Changed main jet from 105 to 115. Kept the pilot at 40. Adjusted the air fuel screws about 3,5 turns out, and moved the pins up 3 spots. Bike would start up and actually run pretty well sitting. But still only with spray at first, then would still start maybe within an hour or two, after that needed spray again. Replaced diaphragm and gaskets on the petcock as well. Took it out for a kilometer ride after letting it warm up and it ran pretty good. Didn't really feel any flat spots or hesitation. Well.... then I decided I'd take it for a little longer ride, about 4 kilometers. Didn't pay attention to the fuel while it was sitting to warm up and it was running rough. I realized it just needed gas, poured a little in, seemed fine. While riding it, it started to get a little rough, and then just died. Thought it was either fuel or battery. Luckily I was at the top of a hill. Rolled down the hill and also changed the fuel to prime again, popped the clutch, it started and went a little ways and died again. Thought after putting it on reserve maybe it was still a fuel thing as I didn't put much in. Put more in, started up and sat for a bit, so I assumed that was the issue. Came back out to start it up and drive the rest of the way to the garage. It started, choke was fully open, and it was idling super low and then just died. After that it wouldn't start even with spray. Took the carbs off cleaned and blew them out again. Diaphragm membranes seemed to develop little holes on all of them by that point, so I thought for sure it was that. So I ordered new membranes on the way, and looked for a temporary fix for a bit, and people said shoe glue. I put the glue on the holes yesterday, and today I tried to fire it up. Nothing... not even with spray. Not even for a second. So that was the short version. Wanted to try and share everything I've done and how it went down. Thoughts? Just weird to me that it started and would run fine, then after being low on fuel, and going for a little longer drive, now it won't start up at all. I've never checked the valve clearance, because I'm super new, and it scares me haha, and it was firing and running before so didn't think it was a problem. Oh, also I checked the plugs they all have spark.

 

did you check to make sure the floats are shutting fuel supply? did you check the float levels too? Sounds like you have a bunch of issues overlapping. start with the carbs running on a bottle. that will eliminate petcock issues. hook up some clear line to the fuel inlet and fill the line up until it stops draining. if it does not stop draining then one or more floats or needle and seats need work. once you get it running and shutting off from fuel starvation you can work on the tank feed issues.

 

Are you me? Because your story rings a lot of bells ...

Did you check the the charge in the battery before and during starting? If you put it on a charger, does it start then?

 

I haven't messed with the floats because when cleaning them they functioned fine, and when i would unscrew the overflow fuel would come out of all of them. I'm not sure if it's fuel starvation since before this time it would fire up fine, or even flood if I wasn't paying attention.

Haha yea, been there done that. It's not a charge issue, cuz it turns over no problem. Just wont' fire up.

 

There is no overflow screw. You were opening the float bowl drains, and confirmed that fuel is getting into the carbs. That does not confirm that the correct amount of fuel is getting in. If the fuel height is low the bike will be hard to start and run lean. If the fuel level is too high the bike will run rich and tend to bog. If the floats don't shut fuel flow off then gas will end up in the crankcase without any outward sign of trouble (unless the whole tank full of fuel drains out).

 

Apparantly, if the charge drops beneath 10.5 V when starting it, the starter will crank but it won't fire.

 

Sorry yea I meant the drains. Ok. I’ll look for how to measure float bowl height and what mine should be at. Again... just weird that it was working and then after a short ride it won’t even start for a second with spray even.

Yea mine won’t even turnover at that low ha. I always keep it on the charger after I try to fire it up a few times to diagnose stuff.

 

Setting the fuel levels

 

Ok so before I did fuel level stuff I checked the spark plugs again. They weren’t sparking to the center electrode or actually two weren’t at all... (sorry I thought I checked them correctly) they’re new plugs. So I brushed them off. And it started right up. Idle wasn’t bad. Just a little rough. Let it run for about 5 minutes. Came out about 3 hours later started it up. Seemed ok at first and after about 2 minutes it just slowly died. Could I have a mixture that is causing some type of soot or something to stop the spark plugs from working correctly?

 

Pull thhe plugs and take pitures of the business end for us to look at. Mark them as to which cylinder they came from, and photograph against a neutral background.

Have you removed the spark plug caps from the wires and checked for corrosion (they unscrew from the wires)? Usually there will be some, and all you need to dpo is trim back the plug wires by about 3mm.

 

Also test resistance 5k +-10%