Periodic shutdown is driving me nuts!!!

This is driving me nuts!! 82 750 Max will run fine and then all of a sudden it acts like someone turn the key off. I need to turn the key off and on, and crank the starter anywhere from 2-20 times, and all of sudden it will fire right up. There are no loose grounds or loose wiring. There is no pattern to when it does this or how long it will take to get it to fire again. Sometimes it will do it once and then it won't do it at all while I go for a 30-40 min ride. Other times it will do it at half a mile, then at 3, then at 1....no relation to bumpiness or smoothness of road...nothing that I can figure out to get me pointed in a direction to start trouble shooting....
Gurus got any ideas?!!?

Keep in mind I am running Harley controls and have eliminated the atari gauges...

 

It may be a shot in the dark, but this really sounds like an electronics shutdown issue. Have you checked the relays (specifically the safety, and ignition)? After that I would take a look at the Coils, TCI, pickups in that order.

I have had coils do exactly what you describe. Run good for a while then shut down unexpectedly. Only after sitting for a while would it run again. Very irratic symptoms.

Ghost

 

Yes very erratic symptons, could be anything from coils relays TCI. I would start looking at the relays first, especially the saftey relays. Unplug the side stand relay and ride, just remember the saftey is dissabled when you do this.

 

I have had very similar issues due to poor battery performance. Your battery could have the right voltage but not be able to supply proper current. It will act like everything is fine and then die; you won't be able to start it for some amount of time and then it will act like nothing was wrong and fire right back up.

Sounds like you may have checked this already, but still, weak battery can cause some of the seemingly strangest behavior.

 

When it happens, again ... try seeing if she'll run on Prime.

I've seen a bunch of Bikes, over the years, that quit when hot because the Hose to the Petcock wasn't actually Vacuum Hose.

The Non-vacuum Hose would collapse on itself shut-off the gas.

Then, check your Alternator Brushes.
You might be "Living-off-the-top of the Battery."

The Battery supplies the system with adequate current, ... but isn't getting Charged ( +14.2 ~14.5V DC to the Battery @ 2000 rpm's & above).
The Battery doesn't have enough Amps.

Measure Alternator Brushes
10mm or less = replace.

 

Mad_Bohemian - I had that exact same problem (in ATL city traffic no less) and for me it turned out to be a battery lead that had just enough wiggle room to break contact intermittently. I strapped the battery down, removed all wiggle, and tightened that problem away. Does the engine die or all electrical function?

I also had a short that prevented the starter relay from functioning properly, but I fixed that today. I don't like electrical problems.


RickCoMatic, holy crap that might be what happened to me tonight.

My bike isn't even home right now, I had her die 4 times and could not make her restart the last time. I walked home 2 miles in the rain to get the trailer. I was lucky I was so close.

Real similar thing. 1982 XJ750 Maxim, starts up perfectly. The first 10-15 minutes of any ride is golden, the engine just sings in all gears and at all RPMs . . . then after that time the throttle response starts getting really choppy and "spongy" and then after another few minutes it's like twisting the throttle does nothing at all - when she finally shut down tonight I had her wide open and couldn't hit 4000 RPM, could barely hold 30 MPH and had to get off the 4-lane.

There was no electrical problem with the lights or hitting the starter, but it was like there was no gas. I think I'll look at the vacuum hose - I wouldn't be surprised if it was messed up, everything else on the bike is screwed. It's 80+ degrees even at night here in Georgia, I don't remember having this problem in the winter. Then again I was in Atlanta then and not taking her up to 60+ mph for any extended periods. Tonight when this started I found myself barely hitting 55 mph in 5th gear with the throttle wide open. Then when I slowed down to make a stop sign the bike just died at 25 mph.

 

Thanks guys, I'll run through the system again and look for problems.
I don't think it's the battery since there is no definable wait-period before it will start after dying. Sometimes it 10-20 seconds, sometimes a minute but it has never been more than that.

How would I check the TCI? I'll take some pics if I get some time today, but that was on of my thoughts. Would it matter where I have the TCI and the heat sink (that finned 2x3 is thingy). The TCI is packed in kinda tight and the heat sink is under the side cover...

What spec should I be looking for for the coil and/or TCI ?

Rick, when I check the alternator brushes, am I measuring the size of the brush for wear??

 

Sidestand switch. If the sidestand switch is intermittent, it will keep shutting the bike off when it's in gear. ANYtime it's in gear.

Betcha. Unless you've bypassed it already.

 

When the bike is running, pull the seat and wiggle/press/etc... on the main fuse and the ignition fuse inside the fusebox. A loose bunch of fuses can cause this, too. Been there, done that.

Dave

 

Yes.
Wear.
Some have a "Wear Limit" line.

Also l look for signs the Brushes are arcing and burning the Orbit Paths on the face of the Rotor.

If the Rotor has scorched marks, ... Scrub them with an Old Style Typewriter Eraser. The "Round" one, ... with the Broom attached.