It finally stranded me.

'85 XJ700N, 18,500 miles, totally stock

I have had a problem with the bike shutting down at idle until it is fully warmed up, at which point it runs and idles perfectly. Recently, it has been hard to start after sitting for several days.
Today it was a little hard to start, with or without enrichment. After riding about 8 miles and having lunch it was a little hard to start and shut down a couple of times. It doesn't stumble, it just shuts down. Got to a gas station and it would not start, although at times it tried to. Went home, got the trailer and came back, and it fired right up but I had to rev it to about 2000 to keep it going until it got warmed up.

The battery is fairly new, stays on a maintenance charger, and spins the engine well. The valves are in spec. The plugs look perfect. It is tuned on the lean side with respect to the pilot screws which I set using a colortune plug. What baffles me is that it shuts down just like it does when I turn off the ignition--instantly. I am thinking a fuel issue--maybe need to open the pilot screws slightly. But I am wondering if there is anything in the ignition that might be causing a problem at idle? I'm getting too old for this.

 

How "fairly new" are we talking? I'd check the voltage drop when trying to start.

 

When was the last time you cleaned the sidestand switch?

That's not likely related to the hard start (though it can be), but it may explain the sudden shutdown.

 

you could start by unplugging the black/white wire from the tci that will eliminate the sidestand as issue if the problem goes away.

I would also clean and inspect the ignition switch, run switch . look for loose connectors in the circuit

didn't you have an ignition issue before something about rain?

 

Battery bought last August. Have not cleaned the kickstand switch but I will. Have not gone into the ignition or run switch. The problem only happens at idle and before the engine reaches normal running temperature, which leads me to believe it is not the the kickstand switch, ignition or run switch. The rain problem happened at normal temperature and was solved by using silicone grease on the wire ends an the lip of the plug caps along with flexible covers over the plug wires from the caps to the coils. (Looks really good!). I am wondering if I have the pilot screws too lean since i set the on the lean side of blue using the colortune plug.

 

Hmm have you set petcock to PRI (if you have stock petcock that is) possible vacuum line is collapsed . Another thing to try is give your carbs a HOT SHOT , drain all 4 float bowls, prop tank up pull fuel line off of petcock , with a large syringe or Turkey baster fill fuel line with acetone/liquid carb cleaner ( I use Berrymans B11) 50/50 mix. Let sit for 45 min , drain float bowls ,reconnect fuel line and set to PRI fill bowls and start bike see if this helps . Other thing possible fuel cap ven is plugged slightly, open cap and see if it runs better.

 

I have the stock petcock which has been rebuilt several years ago, and I do set it to PRI if it has been sitting for a few days. I have also gone through the fuel cap and it vents freely. The carbs were cleaned several years ago and I have not had any issues until the last 2-3 months, so maybe the "hot shot" is needed. I've never done that before or known anyone that did. Is there any concern about damaging the floats and seals? I am still wondering if anyone thinks slightly opening the pilot screws might help.

 

i do, it's easy, it's undoable and it's free.
i find a rich stall stumbles, slows down then quits, a lean stall just stops.
how does it act when it's good and hot?

 

When it is good and hot it runs and idles perfectly, although I have it idling at about 1200-1300.

 

sometimes if my 750 is in that not cold but not hot zone, i give it full choke for "one thousand one" then shut the choke off, no throttle, and hit the button and it starts right up.

 

Does the XJ700 have a separate fuse for ignition system? If so, bad clips? Have you replaced the fuse box.

My XJ550 used to periodically "shut off" just like you describe, like turning off a switch. Would hit a bump, shut down. Would also have it shut down at random. It was corroded fuse clips.

 

The 700 uses ATC fuses. Master fuse in a seperate holder, and the rest housed in the gauge cluster.
Might be a cold or corroded solder joint though.

Carbs might be the issue too.
One thing at a time.

 

The hot shot will not hurt anything it can dissolve deposits , can save you from having to pull carbs possibly. Last week my buddy tried this on his KTM and he got some crud out of bowl ,bike ran better .

 

Have not had, a chance to work with it yet but will this week. Just thinking, how many miles on a set of plugs? These have about 5,000, but look really good.

 

replace at 1300 km 8300 miles then every 12 months or 1200 km. clean and regap every 4000 miles 6 months

 

Thanks.

 

Today I opened the pilot screws about the width of 2 dimes and removed the air filter to clean it. It had some oil on it so I guess I'm getting some blowing in from the engine. At the same time I noticed that the fuel filter was leaking so I removed it and now have a straight fuel line from the petcock to the carbs. Hit the starter and it fired off easily. (However, I did wash some of the oil out of the filter with gasoline, so we will have to see how it works after it has run for a while.)

I was just lucky to find the leaking fuel filter and now I am a little worried about putting another one on. the one I had was the plastic filter with the 90% bend and the stone looking filter. It was leaking where one of the posts goes into the side of the filter. Anyone have another suggestion for a fuel filter?

 

you can get the metal cylinder filters the internal is removable and can be cleaned. the plastic ones do melt after long use there is a thread about it.

 

INLINE FUEL FILTER Longevity Alert


In line fuel filter

 

something like this