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79 SP1000 - Is it fuel flow or electrical?

F

Fish

Just got it firing!
Joined
Mar 15, 2009
Messages
3
I'm a long time browser of this site, but now a first time user.
I have been resurrecting this low mileage (23,000 mi.) SP for about 2 years. Ran fine when I brought it home and put on 800 miles over the next year or so. Last fall the engine stopped for no obvious reason less than a mile from home. Inspection turned up lots of rust in the tank. I had the tank cleaned and coated by a local shop; replaced all fuel lines, cleaned pet cocks and rebuilt the carbs. Also, during the last year replaced plug wires, plugs, starter and other unrelated items. Cranked up the bike this past week and sorted out the recently rebuilt carbs; idles and seems to run fine. HOWEVER - it runs even and strong for less than a mile and then just quits, like it ran out of gas. Let it sit for awhile, it will crank up and go, but less distance.
Since I have been working this issue since last fall, professionals have suggested items such as proper gas cap, ensure a vented one is in use, etc. All suggestions have been tried, yet I have not identified the problem.
Could the problem be something other than fuel? The bike came with the common electronic ignition upgrade installed.
I'm at a loss for new ideasl
 
So it quit after a mile, then restart a little later, runs for another mile and quit again etc.
When this happened to my SPIII I tried all the fuel items, but it was actually a faulty coil, which was breaking down when hot.
 
Nice diagnose Brian... Fish, I was going to say go after the electrical next. Coil would be my guess as well. Next time it quits, carry a spare plug with you, pull the cap(s), and insert on each side to see. Are your coils stock or Dynas?
 
RacerX wrote:
Next time it quits, carry a spare plug with you, pull the cap(s), and insert on each side to see.
Click to expand...
That's far more sensible than I managed. I did check the spark, but by the time I had pulled the plugs out, the coil had obviously cooled down enough, which led me to keep trying all the fuelling possibilities, which included riding for that mile with the filler cap removed.
 
That's a great idea. I don't know much of the history of this machine thus those coils could be older than dirt. Something I should have done previously as a matter of eliminating a potential problem.
Thanks,
Art
 
Since the bike came with the Dyna installed, I don't know whether the coils are stock or not. The coils can be described as light gray aluminum cans. My main ride is a '99 EV11 and no commonality with a lot of the SP components.
R/Art
 
Fish wrote:
Since the bike came with the Dyna installed, I don't know whether the coils are stock or not. The coils can be described as light gray aluminum cans. My main ride is a '99 EV11 and no commonality with a lot of the SP components.
R/Art
Click to expand...


Looks like they are original 30 year old coils. Also since you didn't describe how it died (sudden power loss vs. gradual starvation), also check float levels if the coils are OK.
 
I've said it before, and I'll say it again.. Carburation problems are almost always ignition..:cheer: but..in my experience, a bad coil will start to miss before going tits up, not just suddenly quit firing. You *did* open the fuel cap when it quit, right?
 
I had very similar problems on my SP with 26k miles, I stuck the Ignition lead on the switch into my running lights and fixed it. When I got home I replaced the ignition switch , been good ever since.
 
Chuck in Indiana wrote:
in my experience, a bad coil will start to miss before going tits up, not just suddenly quit firing.
Click to expand...
In my case referred to above, it most certainly suddenly stopped working, no suggestion of missing before.
 
I had a fair amount of coil problems on my SP. Don't know anything about the Lucas Rita.. But failure when hot is typical.
 
Clean all the rust out of the screens at the carb inlet and from the petcock screens. Sometimes, they'll mostly clog such that you run out of fuel in steady-state running but then after it sits for a few minutes, enough fuel leaks in that you can start it again. Same thing happens if the "neck" stretches on one of your float needles.
 
The spare plug idea sounds like the way to identify whether fuel or electrical. Not familiar with RITA, but I've seen semiconductors that run hot, like voltage regulators, become thermal intermittent. You can make them go open circuit by heating and pop back into operation by cooling. A heat gun and can of freeze spray might allow you to isolate it to the ignition box or coil.
 
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