1980 SG cutting out as it gets hot out...

[Bonz]

Hello all!

Haven't been around in a while, my 1980 1100 SG has been a model of reliability and consistency since I did a full carb dissasembly and cleaning last fall. I lurk every now and again, to see what's going on.

Here's what I've got going on now that it's warming up outside. I have not had this issue in either of the previous 2 summers/years since buying the bike. Here goes...

Yesterday, once the bike got good and warmed up (hot, as in normal riding in 90+ degree temps) when I come to a stop, the bike idles well, then quick drop in rpm (250 rpm or so drop) and it quickly pops back up to 1100-1200 rpm where I have set the idle. Seems to do this in a somewhat rhythmic pattern. Then, when pulling away from the stop as I feed in clutch and throttle, it hits a quick drop in rpm and the bike jerks as i try to catch the rpm drop with the throttle, or I don't catch it and it stalls.

I took the bike out early this morning, 58 degree temp, took it for a good ride and it ran fine. Many deliberate starts and stops on an empty 2 lane road, and it would not act up. Rode to work today, as it got into the 70's and the bike got warmed up again, the same pattern as yesterday developed but not as bad, like a lesser version of the same problem.

I have defintely correlated the problem to the increase in outside air temperature, therefore overall higher temps of things on the bike.

SO, do you guys think it's an electrical (coil?) issue as things heat up and get heat soaked or something to do with the fueling? I still have the Octy on my bike, petcocks work fine, tried going to reserve and prime, doesn't seem to make a difference.

What say you?

[CatatonicBug]

Try the pickup coil wires. The wires may be breaking inside the insulation.

Take the timing cover off, and, while running, tug on the wires to see if it changes anything. You may need to splice in new wires.

[Bonz]

Do you feel that is something that would be heat related, or wouldn't it run with the same issues all the time if that were the issue?

[CatatonicBug]

It may be that the extra heat just made the insulation that much softer, exacerbating an existing problem, or maybe it's just a new problem that isn't necessarily related to the weather at all. It's worth looking at either way, since this is a known issue for these bikes.

[Bonz]

I agree, I've seen many posts on the issue with that wire. It's something to take a look at when I can for sure.

So my thoughts on the coils getting hot and malfunctiong, as they are almost 31 years old, doesn't seem to be the issue from what you are saying and what I am describing, yes?

[DGXSER]

It does sound electrical in nature. Perhaps a coil issue or something in the ignition system overheating. But it does seem wierd to be that ambient temperature dependant and not bike temp dependant. I'd say get the bike good and hot like a twenty mile ride or so, pull the tank and check your coil readings. See if they show bad when hot.

[XSokieSPECIAL]

What do your plugs look like and do you smell fuel when it does this.

It very well may be an electrical issue but when mine acted up in the heat it turned out to be carb related.

When was the last time you synced the carbs?

[petejw]

if the pick ups check out ok,
you could be running rich, and with the
temps warming up it could be making it worse,
check your air filter is clean and as xsokie stated check your plugs
to see how there burning.

[Rickrod3]

Mine acted the same

For me it was carbs flooding.
Easy to check.
Pull the air cleaner bottom check for gas.

[shutchis]

Running Lean?

I think you're running a bit lean on one or two cylinders. Try using the enrichment circuit (sometime called a choke lever) and slowly add fuel to see if it makes any difference. Also check your air filter; be sure it's in good shape and sealing. A leaking air filter will also cause it to run lean. You're in Colorodo...altitude and heat will reduce the air pressure. P.S. I live near Houston, we start our days at 80F and go up from there; it's cool today, only 94F. Yesterday was 99F.