struggle struggle... '80 550L starts, idles, dies, then won't restart.

[Guest]

Wow, I'm getting close to ending it all!! lol
I have done what I think is all the maintenance, sensible upgrades, and used quality parts.
The bike began having starting problems last fall. I pulled the carbs and cleaned them well. Again...
The initial restoration was only less than 1000 miles ago. I used all new o-rings from Mr. Barr. Valves were done at this time. Plug leads were trimmed back, new plugs and caps all around. Coil relay mod is done as well. It has always had a finicky start, but never a "problem". It always started and ran great once running.

This spring, it would not fire at all, even with ether. I was seeing intermittent no spark symptoms. My battery tested bad even though it was cranking the motor over for short periods between charges. I replaced with a new AGM last week. My ignitor tested bad to the best of my abilities, so I shot the lock off my wallet and put a Dyna S in. As soon as those two things were done, it fired immediately. Idles so sweetly, it's like a song. A few minutes later, it will die and not restart unless it sits for awhile. I got it running enough to ride 3 miles down the highway to the gas station and back. Started perfectly at the station, and came right home. Wife got on, stalled it, and it would not restart... Let it sit for about ten minutes and it fired right up again. It ran for a few minutes and died. Would not restart again. Wife started it easily this morning, and let it idle. Died after about 3 minutes and would not restart.

I'd rather say I don't have a random NO- start condition, but a random START condition...

[tom203]

Try replacing the 10 amp ignition fuse- it might be cutting off the current to the kill switch and dyna randomly. Gets hot ,opens circuit,and then "heals" itself again after cooldown. Next suspect the kill switch doing the same thing. Extra 3 amp load of starter solenoid goes thru fuse and switch at restart.

[2BRacing]

My guess is that you have a fuel supply problem. Try putting the petcock to the "prime" position, and see if the bike still dies after a few minutes.

If it continues running, the petcock should be replaced. Also check that the vacuum line from petcock to carb is not split open.

Is the fuel tank clean? Maybe a lot of crud has built up around the filter on the petcock, preventing good fuel flow.

[MatBirch]

still having trouble... I did go back through fuel systems, and removed an inline filter. I checked the petcock, and all the lines. Tried running it on Prime. Everything is working as it should. I'm now fairly certain it is NOT fuel related, as I can force the failure far quicker than the motor can burn the fuel in the bowls.
It did get better, which I attribute to the filter removal, to the point I thought I had it. I then went back through everything again, focusing on the electrical. I know it has nothing to do with this particular problem, but I went ahead and put an SH775 r/r in, as I was seeing 15.7V at 5000 rpm.

Anyway- It now fires instantly (the first time) and idles beautifully. I even got to go for about a 5 mile ride. I really thought I had it licked. Here's where I get lost-

I pulled back into the driveway to grab the wife and go for a ride. As I was in the middle of my multi-point turn around, I stalled it, and it would not restart.
Some experimenting over the next several hours led me to this-
If I turn the key off or use the button switch, it will usually start again. If I stall it quickly, by say... dropping the clutch, it will usually restart. If I LUG it and stall it, (as my beginner wife might do, or I did turning around...) it MAY restart, but do it more than once, and it will not restart. It seems as though if you "load it up" or stress it, it will fail.
Once it sits for 10 minutes or so, it fires right up. After several hours of sitting, I can make this scenerio occur at will.

I have searched extensively, and found very little. I found one thread with a long list of exact symptoms, however, no conclusion. Searching the username, I believe I found that he replaced the coils and solved it. Is it possible for coils to overheat and "open" or otherwise fail under load? I have a set of known good coils from a Honda CB 750F dohc that would be simple to hack in there... I know the standard interweb reply is that coils "never fail" and it's always something else. I'm just feeling like I'm out of "something else" to look for

[tom203]

Before you go to trouble of hacking in those honda ignition coils, add a jumper wire to orange/white wire that feeds + to coils and dyna . Drape the opposite wire end some place safe where you can get at it and attach it to + battery terminal next time it craps out on you. This bypasses all ignition circuit switches. If it then starts right up, you know that it isn't the coils or dyna. Of course, you will have to stall it out to kill it.

[MatBirch]

easy enough, thanks! I'll report back...

[MatBirch]

No change. Still didn't restart. I think I'm going to give the coils a try. Sure won't cost me anything but a little time.

[bearrocco]

Having the same problem with the same bike installed dyna system let the bike idle or ride for about 5 minutes it stalls wont restart , I noticed today when I check voltage at the orange white ignition power wire when acting up voltage is around 8.50 volts seems low . when it cools and restarts , its about 10.5 volts any Ideas .

[MatBirch]

OK- all signs lead to FIXED! I couldn't ride it tonight, but I was unable to recreate the failures in the shop, as I was before. I can stall it all I want, get it good and hot, then stall it, etc. and NO failure! It springs to life perfectly each and every time. (Even once when I forgot to plug in the 1-4 coil)
Victory seems to have arrived in the form of the old Honda coils. I had them left over from my CB750F. I had swapped them out with CBR f2 coils for an improvement on that bike. I had to make a quick harness to plug them in, and at this point only have them mounted by one bolt each. I had a nice long length of high tension cable, and the caps on the bike are nearly new, so I assembled all new leads on the coils.
So far, so happy!

[Grimly]

Next time anyone tell you coils don't fail - tell them they're spouting BS.
I've had a few that did exactly what yours did - when hot they'd go intermittent.
Oddly enough, the most recent one to do that was one of a pair of CBR1000 coils, the same as you're now using. They were 20+ years old, though. When working, they were excellent coils on the Suzukis.