running on 2 cycinders?

[Paul F]

I have a 1982 GS1100E. Yesterday it cut down to two cylinders after running the rpm up to 7000-8000 in second gear. I limped home (10 miles). When I got home I restarted it and had the same problem.
This morning I started it up and all four cylinders are running fine.

Any ideas as to what went wrong?

[PoPr]

Check your contact breaker gaps... My bike ran on 2 cyl, and I was going to check the gaps... Look at what fell out when I took the cover off :shock: link
The tip of the contackt breaker had snapped clean off. No wonder my bike ran like sh*t.. =)

[nabrams]

Definitely check your signal generator (as suggested), but don't rule out the possibility of a bad coil. When a coil is border-line it wil fail when it heats up - so the bike will run fine when first started up and then will start missing as the coil gets hotter. Eventually the bad coil will fail altogether. If the coils are the originals there's a strong chance that one is failing.
Identify which cylinders stop firing after a long ride.
Then switch the coils and see if the problem moves to the other cylinders.
This comparison will tell the tale.

[Paul F]

Check your contact breaker gaps... My bike ran on 2 cyl, and I was going to check the gaps... Look at what fell out when I took the cover off :shock: link
The tip of the contackt breaker had snapped clean off. No wonder my bike ran like sh*t.. =)

That looks pretty bad. Do you think the bike would run on 4 cyl. with that problem. Mine did the next morning?

[Paul F]

Definitely check your signal generator (as suggested), but don't rule out the possibility of a bad coil. When a coil is border-line it wil fail when it heats up - so the bike will run fine when first started up and then will start missing as the coil gets hotter. Eventually the bad coil will fail altogether. If the coils are the originals there's a strong chance that one is failing.
Identify which cylinders stop firing after a long ride.
Then switch the coils and see if the problem moves to the other cylinders.
This comparison will tell the tale.

Can you do a coil test it all cylinders are working. My problem is intermitent.

[nabrams]

Get those coils nice and hot (bring the bike to red-line if necessary) and the problem will be forced to surface such that two cylinders will just stop firing (just like it did the way you mentioned in your first post).
At that point, get off the bike, and crank up the idle adjuster so that the bike keeps running on two cylinders. Then pull plug wire #1 - if the bike dies, you'll know that the coil that fires 1 and 4 was still good - then re-attach wire 1, restart the bike, and pull wire 2 just to verify that RPM doesn't change - all this would clearly indicate failure of the coil that fires 2 and 3. If the bike does not change RPM after pulling plug wire 1, then you'll know that the coil for 1 and 4 is the culprit.
I think you get the picture, right?
If the bike runs just fine for the first 15 minutes even at fairly high RPM then it is alomost certainly an "electrics-heating-up" issue.

[PoPr]

That looks pretty bad. Do you think the bike would run on 4 cyl. with that problem. Mine did the next morning?

I´d say, that the bike will definetly NOT run on all four if the breaker is broken, like mine was.
I also vote for checking wich cylinders that are not firing (1&4 or 2&3) when coils are hot.

Is the bike running on two cylinders when cold also? Then you could just check your coils resistance with an Ohm-meter.

[Paul F]

The bike seems to run on all four when cold. Can you check the coils when running on 4 cyl?

[PoPr]

The bike seems to run on all four when cold. Can you check the coils when running on 4 cyl?

Well, if the bike is running on all four when cold, it´s really no point to check your coils when they are cold, ´cause they will work fine then
I´d say, check them while they are hot as nabrams recommended.

Does the problem occur at a specific RPM? Or just the hot/cold thingy? If its just the hot-issue, the RPM-thingy doesn´t matter.

[crag antler]

Wow and I was going to say my GT250 runs on 2 cylinders but then thought about it 8-[ :-D