Signal Generator 101

[Thomas Kenny]

Just finally got my Vance and Hines pipe on my 1984 GS550ES. Sounds great!!

HOWEVER!! Bike started to run poorly after riding it for 20 or 25 miles and got to the point that it would only run if I kept the revs up on the centerstand. Then just as my dear wife walked into the garage, I got a BIG backfire, and bike will not start. So I pulled all of the plugs and grounded them and got good spark on all but number 4 cylinder. I unscrewed the sparkplug cap, cut about 1/8 in. off of the high tension lead and screwed the cap back on which brought a good spark back to the cylinder. Plugs on first pull were wet with fuel. Still won't fire? So I did a check on the Signal Generator and the book calls for 250-500 ohms and I am getting about 50 if I am reading my ohmeter right. SO! I got spark and I got fuel, but no fire??? Question? will the coils fire the plugs out of time if the signal generator has failed? I am getting GREAT spark? I am really stymied on this one. Don't want to try anthing more for fear of damaging the lower end if I do get fire but out of time.

Any ideas out there? Thanks

[Redman]

If you were getting any good spark on 1 or 4 and 2 oe 3 then you know the signal generator is good. The signal gnerator is basically wire wound into coils, so it is eiter going to work or not work, I dont think its gonna work but after a delay and fire ignition at wrong time. You say you are now getting good spark on all cyclinder (after triming the one lead).

Lets take a look at your ohm meter. If you short the two leads together, does it read zero ohms? Is it digital meter? Or analog with meter needle that can be zeroed with a zero adjust knob? If it doesnt zero it probably needs new battery. If it is analog, there may be a couple different ranges for the ohm selection, need to be aware of what you select and read apporiate scale on meter face.

I can not address any issues relative to the aftermarket exhaust.

[Thomas Kenny]

Thanks Redman, I have an analog two range Ohmmeter. I pulled the signal generator off of the bike. The magnets in the pickup heads are broken as I lifted the pickups off of the backing plate the magnets stayed on the backing plate and are in pieces. I bought this set used from a motorcycle salvage yard about three years ago. My bike was running well and I ride it all of the time. The backfire that I got out of the muffler was huge? The bike then struggled to run and finally stopped firing at all. I am going to order a new signal generator although I am with you that these must be operational as I am getting a substantial spark on all four plugs. I guess I will start probing into the fuel system. Not sure if a backfire can damage the rubber diaphrams that lift my slides, but the backfire seems to have started all of these problems. I'll sort it out in time. Thanks for your reply. Tom

[tkent02]

Let's see, new pipe, and a few miles later it's not running so good.....

I would be checking compression. A new pipe makes it run lean, burns up some valves, so no more compression, all the spark in the world can't fix that. I'm not saying that is your problem but it seems pretty likely, a change in pipe and mixture won't effect the ignition one iota.

By the way, does anyone know what an iota is?

[Thomas Kenny]

Thanks Redman, I used a friends digital ohmeter and got 372 ohms on one generator and 384 on the other well within the range of 250-500 in the book. So my generators are OK. Next purchase will be a digital Ohmeter. I just read my analalog incorrectly.

Tom