'81 GS550T idle and high rpm issue

[Badooka]

Yes there is, having clean slides won't make a difference in adjusting them so they are fully open and the slide is even with the throat in WOT- this is a small item that can be missed and you'll never know if the bike is operating at top end-

[heater63]

So I think I've determined that this is an ignition issue. As I mentioned before, last week I noticed that the plugs on cylinders 2 and 3 were not firing. So I ordered new Dyna DC1-1 coils and replaced both of the original coils. I test them after installing and verified that all 4 plugs got a nice big blue spark. Today I tried starting up the bike again and noticed that the headers on cylinders 1 and 4 were very hot, but 2 and 3 were just warm to the touch. So I pulled the plugs on 2 and 3 and saw that they were not firing (well sometime I would get a single spark if I tried for a few seconds).
Does this sound like a bad ignitor? Do they fail intermittently? Seems strange that the coils seemed to work just fine 2 days ago ...but now I am seeing the original problem.

Any ideas?

[Nessism]

I'd check voltage at the coils. Should be battery voltage or slightly less.

[heater63]

Hey Ed, I checked the voltages at the coils. They are both getting approx 8.8V. It sounds like it should be closer to 12V. Is that a symptom of a bad ignitor? Also, I followed the ignitor test outlined on BassCliff's site ... (using a multimeter to bypass the signal generator and fire your plugs.) I was unsuccessful. I did however verify that the signal generator had a resistance that was in the correct range.

[Nessism]

Resistance in the wiring harness knocks down the coil voltage, which effects spark. Your coils should be getting at least 11 volts, or more. You can try cleaning up the harness connectors or look for the Coil Relay Mod on Cliff's site. Once you get your head around what needs to be done it's really easy.

You can grab power from the accessory screw on the fuse block.

Good luck

Edit: http://members.dslextreme.com/users/...relay_mod.html

[Badooka]

Make sure you hear the click on the wire to the coil post- no click it's not going to fire.

[heater63]

I will definitely perform the coil relay mod described on Cliff's site. But, if I failed the ignitor test, could a bad ignitor be the source of my drop in voltage at the coils?

how does the dyna S ignition work? does bypass the original signal generator and ignitor?

thanks for your help everyone.

[Steve]

..., could a bad ignitor be the source of my drop in voltage at the coils? ...

No, the ignitor has nothing to do with supplying any voltage to the coils. It only switches the grounds from the coils. Yep, that's all it is, ... electronic points.

You mentioned earlier that your coil voltage was 8.8. What was the battery voltage at that same time?

Please do a couple more quick tests before replacing any parts, it will help tell you whether you really need to change anything:
Go back and test your coil voltage again. Was that with the engine running or engine OFF and key ON? Either way, check the coil voltage, then right away, check the battery voltage. Or, better yet, put your red meter lead on the battery positive terminal and your black meter lead on the orange/white wire at the coils.

Getting separate readings, you will have to do the math to see what the difference is. Doing it the second way, it will tell you directly what the voltage drop is. You are looking for as small a number as possible, one volt is not bad. Two or more volts, and you might benefit from the coil relay mod.

.

[heater63]

So guys.... I performed the coil relay mod and that worked great. I read like 11.2V at my coils now. Earlier this week, I was still having an issue with not getting spark on cylinders 2 and 3. I double checked all my wiring to the coils and ignitor and found that the ground on the ignitor was pretty loose. I fixed the loose ground and now all the plugs fire great. However, I still don't think I'm getting combustion on cylinders 2 and 3. When I feel the exhaust headers .... cylinders 1 and 4 are extremely hot. but 2 and 3 aren't very hot. i know this isn't the most scientific methodology, but if the headers for 2 and 3 arent hot and I have verified the plugs are firing .... that leaves the carbs again.
As a recap, I just finished rebuilding the carbs 2 weeks ago (tore them all apart and soaked for several hours in carb dip, replaced o rings and jets, pilots 2 1/2 turns out). My symptoms are that I need to hold the throttle and keep the rpms at like 2500 rpm to keep the engine from dying. Also, if I rev the engine, I can't get it to rev past 6000 rpm. And if I suddenly close the throttle get the rpms below 2000 and open it up again, the engine can't recover and it dies.
Do these symptoms sound like I'm only running on 2 cylinders?
Any ideas on how I should proceed with my troubleshooting?

Thanks everyone, I appreciate all your help and input.

[althomas101]

Since you skipped the carb boot o-rings you might want to do that so you can ensure your not leaking air (Tip: buy a cheapo impact driver to remove the screws). While your waiting for them to come in the mail check your valve lash. And since you have to remove the carbs again LOOK at the slow jets to see if you can see light through all of them, just because they got a soaking doesn't mean they are clear. Also swap the #2/#3 slow jets with #1/#4 that way if the problem moves you rule out ignition. Good luck!

[heater63]

When I rebuilt the carbs, I ran a wire through all of the holes on the jets and carb passages to make sure they weren't plugged, per the procedure Cliffs website.

I know I haven't got to the intake boot O-rings and valve adjustment yet. I guess I just want to see if anyone else here agrees that my symptoms sounds like I'm only running on cylinders 1 and 4 ... or other ways I could verify that assumption.