Help! Why does it keep shutting off?

First off the bike is an '81 Seca 750. About a month and a half ago it started this problem and has slowly been betting worse. It started as the bike would shut off while I was driving but it would start right back up on its own in less then a second. Then it began shutting off when I would put it in gear for the first time (it would usually sit about a week between rides). It might take 15 starts to get it to stay running. Now it sometimes shuts off when I put it in gear even when the bike has been running for a few miles. Basically it will cut out at any time and although it has not left me stained I thought I was going to be today.

When it turns off it is like hitting the kill switch, instantly off RPM's drop strait to 0. I was thinking about the side stand switch but I put it away running and use the center stand, the switch does not appear to be sticking either. I tried to slowly put it in gear, as I move the lever the neutral light will turn off and the gears will rub but once the gears engage one another it shuts off.

Any thoughts as to what it could be? I think it is electrical but there are so many switches and relays on this thing that I am lost.

 

I know this sounds odd but... is your main fuse sliding around in the fuse box? Mine was doing that so I put a piece of electrical tape on it. Just a thought.

 

Fuse's look good. I replaced the fuse box with one from Radio Shack a few years ago.

 

Two other causes would be the engine kill switch needs cleaning or the TCI is going out. The fuse box digi3e mentioned is the main cause of this problem.

 

There might also be a short in the kickstand safety/kill switch...?

 

thats what i was going to mention , does your kickstand have a safety switch on it? if so check it out cause if its acting up it will act like the kill switch and shut things down.

 

Another thing that can cause this type of problem is loose/dirty battery terminl connections. Be sure to check the bolts holding the positive lead --> starter solenoid, and starter solenoid ---> starter.

But this sounds like a sidestand switch problem to me also. You may be able to find where it plugs into the main harness and simply bypass the switch with a jumper and go take a test ride. If it doesn't start at all after jumping the harness side, disconnect the swith entirely and try that.

HTH,
-Matt
83 xj9

 

Lift the fuel tank. Unplug the relay under the frame closest to where the tank bolts down. Test for the symptoms you outlined.

Symptoms gone? Yes?
Service relay.

Place relay in the jaws of a vice and tighten the jaws of the vice until it is impossible to apply any more tightening force. When the relay is squeezed flat; remove it from the vice and skip it across the surface of a pond.

Get new or known-to-be-good relay.

Special Note: The safety relay IS NOT THE SAME as all other Yamaha relays.

The generic relay gets the "Signal voltage" across the TOP two, side-by-side spades (viewed horizontally).

The SAFETY relay gets the "Signal voltage" across the LEFT two, over - under, spades (also viewed horizontally).

See what happens when you unhook the relay.

 

Thanks for all the advice, I will be printing out this thread and testing everything tomorrow. Hopefully I can get this figured out soon, fall break is coming up and it's the bike or the bus that I have to take home.

RickCoMatic,
What do those relays do? I see there are several of them but I am not sure of there actual function.

 

The ONE Safety Relay takes signals from the sidestand, clutch lever switch and the circuit that indicates the bike is NOT in neutral and does not allow the bike to start or run if any are closed when the start button is pressed.

If the relay is malfunctioning, it will disable the ignition and prevent the bike from starting ... or ... kill the ignition circuit if the bike is running and placed in gear.

The WRONG relay will ALLOW the starter to engage ... with the bike IN GEAR and the clutch lever released ... a very dangerous condition.

 

OK, I check the side stand switch, seems to be working fine.

Battery connection is also fine.

I pulled the relay nearest the tank mount and the bike would not start, do I need to run a jumper wire in the harness when I remove the relay?

 

Nope. Without the relay you should be abale to get the bike to start and run without cutting-out.

Here's the "But":

The bike needs to be in Neutral to Re-start it. The wiring diagram's are almost impossible to read all in black and being so small.

However, it looks like Neutral is the default safety circuit. Looks like if you're running the bike and shut it down or stall it ... you'll need to shift the bike into Neutral to get the Starter Motor to engage.

(It looks different on the 650 and 750Seca. Anyway, the way I see it, the Neutral light circuit is part of the safety circuit and the bike might have to be in Neutral to get it to go.)

However, it does look like there's nothing wired to the ignition that will make the bike shut-down unless you Kill Switch it ... or, stall-out!

 

OK, now I am discouraged and very, very frustrated. I had my brother mail me the electrical parts from my parts bike in hope that I could replace whatever is wrong. Over the summer I plugged each relay into his Seca and they seemed to work, the bike still ran and everything worked.

So I go out to the parking lot today for some plug and test (in the 40 degree weather). Well wouldn't you know it but the bike starts up fine, I warm it up for a few minutes and it runs normal the whole time. So I try replacing the relay under the left side cover and go for a ride, the bike shut off 2 blocks down the road. I coast to the side and it restarts without hesitation and I am off again. Now I do loops staying near the apartment and the bike runs great for the next 20 minutes. Then it shuts off. I pulled over and tried to restart it but whenever I would put it in gear it would shut off again. So now I lift the tank and start swapping relays I tried the 3 different relays that I had (not sure what one is supposed to go in there since they all look the same) and I tried putting the original relay that was under the left side cover back and then plugging the new relay in under the tank, still nothing. Finally I went back to the original setup and the bike didn't work on the first try but then worked on the second time I put it in gear.

I quickly got back on the bike and rode it 100 feet and it shuts off again. This time I start thinking, that most of the time it will cut out under acceleration, so with the bike in neutral I start it back up, put it in gear and it shuts off. Well now I start it in neutral and rev it to 7,000 RPM and hold it there for a second, it didn't miss a beat. So I let it drop back to idle and put in gear and the stupid thing shuts off again. Now I am MAD!! I then try to restart it and nothing happens, nothing at all. The lights are on but nothing happens. So right now it is sitting on the side of the road.

This bike has rarely given me problems, it made it coast to coast this summer, and now it is just so frustrating.

So, can I bypass all these relays? Any suggestions short of a match (that is plan B)?

 

I just went out to more the bike, it is street sweeping night. It fired up and ran ok, put it in gear and drove it the block to the parking lot then just to see what would happen gassed it. Sure enough as the RPMs rose it shut off. Then when I put it in gear it would shut off again.

So to recap it shuts off randomly, more often when under acceleration but sometimes while holding the throttle steady. When I restart it sometimes it will shut off when i put it in gear, sometimes it is ok.

 

With all this going on ... now, the first thing I'd do is swap-out the Ignitor.

If you swap-out the ignitor ... for one that is known to be good ... you'll either be cured, or ... we're going to have to do some serious electrical trouble-shooting.

Hope that the Ignitor swap does the trick ... if not; we'll need:

12 V Test light.
Multi-meter.
9 V (Smoke detector type) battery.
2 Pair - Red & Black Test leads with alligator clips on both ends. (Short money at Radio Shack)
Spray electronic contact cleaner without oil base ... the disappearing kind.

Someplace inside with good light to shake it down.

 

I do have a spair Ignitor here but I have never tested it, is there a test that I can do off the bike for it? I guess I can try to plug it in tomorrow and hope it makes a difference anyways.


I really wish I had my Yamaha manual here.

 

The best test I know is: Plug it in ... see what happens.

In the mean time ... a couple of things to check-out.

Pull the left side crankshaft cover and inspect the whole area for moisture or anything loose. The mounting bracket for the ignition contacts might be loose in there.

The Clutch lever safety switch comes into play; too. Shoot a quick shot of WD-40 into the guts of the clutch lever switch ... and then "Work-it" a few times and give it another quick blast.

If the situation gets totally out of control ... and, we don't make any good progress emailing ... load it up and bring it to My Little Shop of Horror's, near Boston. Good things happen here.

It's sorta like "Hogwart's School of XJ-Wizardy and Magic."

 

Well I know it is not the clutch switch. I forgot to mention that that is bypassed. The original owner bypassed it and I have never bothered putting my spare one it. I did check it today and the connection is still good. I will also check the left side cover, I forgot about the advancer in there.

I just wish it wasn't electrical; I hate electrical stuff, especially when I am not back in my warm garage with lots of time. Either way I will have to make it out to Boston in the spring/summer or whenever you have your next carb. clinic. It would be nice to ride with another XJ’er. You have some nice roads out there too. I took rout 2 into Boston this summer, the western part had some real nice roads and overlooks 8) .

 

I had this happen on my XJ some years ago. It was a faulty side stand switch. In my case the shaft on the switch that the kickstand spring pulls out was broken. So the shaft would stick sometimes and others not. I discovered it by pushing in on the switch shaft. Since it was broken I removed the spring that pulls the shaft out and then removed the broken part of the shaft. The switch was now "on" all the time. Has worked ever since.

 

I took the BlueMax problem and the PO fudging the Clutch switch into consideration when I wanted the Safety Relay pulled and the running situation -- post pulled-relay -- checked out.

I've re-read the thread a few times for some clues to go on. See if this makes sense to anyone.

Since the bike will -- occasionally -- start and make high rpm -- in Neutral ... but, shut-down immediately when placed in gear -- indicates that there IS a problem with one (or more) of the Safety features.

The bike shutting down when placed in gear is the safety feature of the Side Stand circuit.

1. Rule out problematic side stand issue. UNPLUG the Side Stand lead.
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Bike runs good at higher rpm's -- dies at 3-thou and below. This is a can of worms. We got to pull the worms out one at a time.

The bike (assuming the brushes are within specs) makes a bit over 14 Volts when it gets above 2,750 rpm's. The 14 Volt push is high enough to overcome a resistance somewhere.

1. The Ignition fuse contacts in the fuse panel would be the Prime Suspect.

BUT <--- That's the BIG but. The bike has had multiple jump-starts from a source exceeding the capacity of the Voltage Regulator. The Regulator has been damaged to the extent that it fails to provide any current, at all, to the system, unless the alternator is rotating at high rpm's. Below 3,000 there's no current to the battery. The bike runs on the limited power supplied by the battery -- with possible high resistanses (Fuse clips, and aged contacts) complicating matters further. Once the limited reserve in the battery (20-minutes) is used-up the bike quits!

2. Unplug Voltage Regulator connector and inspect plastic surrounding the red wire for signs of overheating (melting) and the spade connection for bluing or arcing. This happens when a jump-start goes bad. Likely to happen immediately if the HOT wire is connected BEFORE the GROUND wire. Voltage Regulaters for these bikes actually pollute ebay!
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Least likely; but never-the-less something we need to consider ... is that the bike is possessed by Evil Spirits who hate you. In which case, you're going to need:

Some candles, a goat and a couple of live chickens! : )