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

 

Apparently the problem is fixed. As indicated earlier, I opened the pilot screws slightly, less than two dime widths. I also noticed that the plastic fuel filter was cracked and leaking so I replaced it with an Emgo filter similar to the one XJ550H suggested. Now it starts almost immediately and seems to idle well even when cold. I am tempted to ride it to work tomorrow but will probably wait until the weekend to test it. Stranded wasn’t a good feeling.

Toomanybikes is sending me an air box duct, so when that gets here I should be all set—at least I hope so. Thanks for all the input and hopefully this thread can be put to rest.

 

You have a sediment bowl on each carb and one on the petcock, why do people insist on putting a filter in-line?? It's just asking for fuel problems.

 

there's plenty of reports of that petcock filter floating loose in tanks. So the next stop would be the beanie filter on the needle valve, that would plug up in a second, most of them are plugged or rusted and never replaced. The next stop, the float bowl, how long would it take a chunk to swirl around
in there and get sucked into the low speed jet?
i don't particularly like to clean out carbs.
it's better to have it and not need it, than need it and not have it
how does it cause problems?

 

They restrict fuel flow more than they do good in my opinion. I dunno how many 2-strokes I've had to pull filters off of because they were running lean from not enough fuel flow. If the system was pressurized, OK, a screen filter would be fine. It's not, though. If you have a lot of floating debris in your fuel tank, including a fuel filter, then you should probably address that instead of just sticking an inline filter in. There is a lot more negative pressure at the petcock than there is in the line above the carbs which is why the filter is located there.

 

The Emgo filter I used has a 5/16 inlet and outlet and a copper screen as the filter element. It is larger than the plastic ones and fuel literally pours through it. If I were using that much fuel I probably couldn't get more than 4-5 miles out of a tank of fuel. My carbs do have the little screens over the needle valves, but it's a lot easier to clean the Emgo filter than taking off the carbs.

 

I can take my inline filter out and the bike runs just the same as it does when its installed. Piece of mind goes a long way especially when a bunch of time and effort goes into making the carbs spotless. Even good filters cant catch absolutely everything.

 

It's fine if you actually know type of filter you should be using and what the flow should be. Most people are going to just go to Autozone and pick up the cheapest filter that will fit the hose. As a general rule gravity-fed systems should never have an in-line filter. They don't come from the factory with one for a reason, there is no negative pressure void in the line to support draining and you just introduce an air pocket mid-flow.

 

I get my filter at auto zone special order it is rated for 4 cylinder motorcycles.
but you are correct that some people put just any filter on and have issues.

many things don't come from the factory and the reason is financial .
compare the 550 seca to the euro 550.

euro 550 has dual disc, oil cooler, nice shifter mechanism like my 750 all because factory had to hit cost factors to sell bike in North America.

Yamaha did not intend for the XJs to be around for 35 years, which is why you need a filter
new tank no rust very little is going to happen and if it does $$ service call to the bike shop.

 

That custom Yamaha filter petcock was WAY more expensive to design and produce than to just use an existing line filter and tank pet from the general market.

 

Well, I rode it to work today and it started and ran well. However, when I got home I noticed that at idle it would stumble slightly when I bumped the brakes. I thought that was sort of odd. Any idea why or if I should be concerned?

 

with the way Japanese manufacturing works I doubt the petcock and design belongs to yamaha

 

that's what i've done for the last 10 years

i put "negative pressure void" in the tank every fill up, great stuff, smells good to
sorry, one too many

 

I do not have an answer to this question. can you tell us more about when this happens?
are you at a stop when this happens? or coasting along?

 

Floats may be too low?

 

C

As far as I can tell it only happens at idle. I have heard that the alternator does not cut in until about 2000 rpm, so I assume that hitting the brakes puts a draw on the battery and that somehow has something to do with it. But then I really don’t know much about the electrical system.

 

check your battery voltage and alternator out put.
per instructions in this thread
The Ultimate Relay, Switch, Sensor, and Diodes Guide

 

Thanks for the link. Somewhat intimidating for someone who does not like electrical issues. I will give a shot at checking everything this weekend, but I have determined that it only happens at idle when the brakes are applied. Have not check it with the blinkers but I will.

 

if you have low output and/or bad battery, amp draw of brake light may be causing issues with the tci or just stressing the alternator.
causing alternator to drag is the best way I can describe it

 

That is what I am thinking and afraid of. The battery is not too old so I’m afraid that’s not it. That would be too easy.

 

how low is your idle? maybe 50 more rpm and it won't happen

 

I have thought the same thing, because when fully warm it idles around 1300, and cold less than 1000. I have not increased the idle because I didn’t want any higher idle when warm.

 

Check tbe case and frame ground connections. No paint or corrosion between the ring terminals and the mount points is best. Also make sure the battery ground wire is secure and there is no play where the wire is crimped.

 

you were having issues then changed fuel filter because old filter was cracked. adjusted mixture screws. have you installed the air box duct yet?
duct install may need some tune up adjustments as it does affect air flow.

 

Got the air duct and it’s in but I really had a chance to get it fully warmed up yet—hopefully today. Fuel filter is in.

 

Started it today. Battery reads about 12.6, and drops to about 10.10 when cranking. When cold at low idle, slightly less than 1000, battery reads about 12.27; at 1500 rpm it reads about 12.6; at 2000 it reads about 13.1; and, at 3000 it reads about 13.6. At cold idle if I hit the brake it drops to about 12.1 and may stall. At higher rpms it still drops slightly when the brake is applied but doesn’t seem to effect the engine. Any problem with those numbers?

I also think that I may be dropping a cylinder at cold idle, so maybe I am still a little lean on that cylinder—- no idea which one yet.

 

* approximately 500-2000 rpms: 1.8 volts gradually increasing to 14.2 volts
* 2000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all models except XJ700-X and XJ750-X)

If your charging voltages are too low, suspect the alternator brushes first, then perform the alternator stator and rotor checks as described in the Alternator Section.

your brushes need to be checked how to in this link.

The Ultimate Relay, Switch, Sensor, and Diodes Guide

 

Should I just go ahead and get new brushes or is there some way to check the ones I have?

 

you start by ohming the wires externally to alternator to see in it is needed to open up.
then measure length of bruhes 11mm is min. spec and rotor will need to be cleaned with hard art eraser and clean the crumbs with canned air and electronic spray cleaner do not overdo it.

the way I think, if I am going to open the cover the brushes are going to be changed. you may also consider replacing the brush holder

 

I have been trying to buy a house—unsuccessfully unfortunately—so I have not done anything yet. Not sure how to “test the ohms” and can’t find anything about it in my tech manual. How would I go about that and what reading am I looking for?