Wiring: Tach/Headlight/No Start

[corey]

Here's the deal. On my way to work today, my bike was running terrible. Cutting out, stumbling, popping from the exhaust. I was confused, since I went through the carbs last week and the bike has been running great for the last three days. Well, when I got a chance to look at it, I realized the Reserve Lighting indicator was on. So I decided to check that out first, in order to set aside my frustration before tackling the poor running problem.

Alas, I found no obvious problems, though I did note lots of cobbled up wiring from the PO. After more examination, however, I found that the RLU light came on, even though both the high and low beams of the headlight worked (!!!). Also, when I toggled back and forth between high and low beam, my tach would jump up to an unspecified reading, then fall back (either immediately or upon switching back to low beam).

After a couple hours of electrical analysis, I figured I was getting no where and would examine the poor running condition. I took the carbs out and tweaked some, then replaced them. Whalla! Ran like a charm... WITHOUT THE RESERVE LIGHTING INDICATOR ON. :| "WTF?" I said to myself. By this time I was tired of tinkering and just crossed my fingers in the hopes that the electrical grimlin had died.

After a few hours, it was time to ride again. This time however, the RL indicator was back, along with the poor running condition (stumbles, pops, and curse words). I figure I have a short somewhere but lack the appropriate wiring diagrams (for now: thanks Hammer!) to diagnosis this problem myself.

Anyone know what is going on??! Any clues as to which wires are screwed up, if that is the case??? Thanks in advance...

[planedick]

WTF

Sounds like a loose connection on the headlight circute. Do you have a good connection at the fuse block? I mean are the fuse clips tight on the fuses? If you have the original type fuse block put a small "O" ring around the ends of the clips to keep the fuses tight.

[corey]

Good suggestion. Just so happens my fuse panel is all messed up, what with the PO putting too high an amperage of fuse in the headlight spot. The wire insulations were melted on both sides of the fuse before I repaired them!

However, can that cause the crazy jump in my tach? Also, would the headlight fuse have anything to do with my bad performance? I was thinking it was something with the ignition, as both the tach and performance were being negatively effected.

[mitch]

did you check

Your pick up wires??? MITCH

[TopCatGr58]

Hey Corey,

A bouncing tach needle can be an indication that the charging system isn't working properly, trigger signal for tach comes from one of three white wires for charging circuit. IF the battery power gets too low, like below 10.25 volts, the TCI won't work properly, and can cause poor running as well! Check your battery, and recharge it, and then see if bike runs okay. Then, check for ~14 volts at 2500 rpm, if still only 12 volts, then it's not charging properly, or the voltage reg/rect isn't working right!

So...aside from your fuse block, sounds like you need to really inspect, clean ALL of your wiring connections. Corroded connections are the most common reason for Gremlins! And causes more resistance, which may also be a reason why the P.O. put in higher rated fuses. But also will need to check for bare rubbed wires in the headlight housing, and where the wires move/wiggle when the handlebars are turned, possibly rubbing against the frame!?
T.C.

[prometheus578]

Like Topcat said, if voltage gets too low, bike can run poorly. Had similar prob with jumping tach. What spooked me was that if I used a turn signal when it was jumping, the bike died. (I spook easily on long trips)
Had a bad connection at the in-line fuse that I had spliced in for the main. Was heating up and melting the plastic. Spliced in a better brand of fuse, and hooked up spare regulator and no more probs. Which cured it, I don't know. Corroded connections are the root of all evil.
Oh yeah, also had a cargo trunk with four bulbs, so that was sucking down some juice, too. (disconnected that real quick.)

[skids]

Re: Wiring: Tach/Headlight/No Start

It sounds to me like the battery is on its dying bed. They can get hot and short internally. If this happens, they can be like a big resistance in the charging circuit. Remember that the headlights, the tach, and the black box all need a minimum voltage to work. I had a battery fail (suddenly) where the headlight went out first, then the tach, and finally the bike started running like you described until it just quit.

Hope this helps...

[corey]

Well, I checked my battery: it read 12.4 volts with the engine off. I already had the bike dissambled partly, so I haven't checked it with it running. Besides, it won't run past idle (dies if you try to rev it AT ALL), so I'm not sure how accurate a running test will be.

On the other hand, a friend and myself checked all the connections and they appear okay. Cleaned the ones that needed it, but they didn't need much. No bare or rubbed free wires, that I could see: I might check again. Also, I removed the ignition coils and checked the ohms on them. The primary circuit for the left coil read 2.8 ohms, with the secondary reading 28.4k ohms. The right coil also had a primary circuit reading of 2.8 ohms, but it's secondary circuit had a reading of 23.3k ohms. The bible says that the given figures (primary circuit: 1.5 ohms, secondary circuit: 15k ohms) should be accurate at 68 degress Farhenheit, but the shop I was in was about 83 degrees. Is this temperature difference the reason my readings were off? ...or are my coils just fried?!?

[Dragonrider]

hmmm 12.4volts on a digital voltmeter? That's actually quite low for a fully charged battery....should be more like 13.1...

You might turn on the key and see how far that drops...(shouldn't drop very far at all on a charged battery....)

Good luck!

[TopCatGr58]

Corey,

Sounds like someone has put in different coils. The OEM should say on their side, "use external resistor" meaning that they are the 1.5 ohms kind and use the Ballast Resistor to keep from frying them. However, the newer 81-82 model uses the higher resistance coils, ~2.8 ohms, and NO ballast resistor, and they Don't say anything about using external resistor.

Your secondary resistances may be varied by the condition of the spark plug caps, you probably measured with them on, and they have separate resistances from 5-8 kohms each. Take the caps off and remeasure.

If you do have the newer styles coils, then you need to bypass the ballast resistor to get the proper voltages to the coils, just unplug the resistor, and jump the wires together.
T.C.

[corey]

Hmm... this is all making sense now, TC. It really does sound like I have a later model coil... As a matter of fact, a lot of stuff on my "79" is later model. I wonder if my bike isn't actually an 80. Do one of the numbers in the VIN indicate production date? 3h3014937 is my VIN.

I'll double check the battery... from what you say, Dragonrider, it does sound a bit fishy.

Thanks to everyone by the way; all of you are definitely helping me along!

[TopCatGr58]

The Vin guide referencing the 1st 3 items, 3H3, shows it's a 79! But no telling what P.O.'s do to these things before "WE" get ahold of them!
T.C.

[corey]

True true... it was just a wild jecture, anyway. I'll work more on the coils/battery tomorrow and get back to you guys.

[corey]

Okay, so the spark plug caps definitely add more resistance. The ohm reading with the caps off were 11.5k ohms and 11.8k ohms. So this means my caps are bad, correct? They shouldn't be resisting this much, I'm sure. I just need to look for the 5 ohm caps, right? I know MikesXS has them, but I'm going to look locally first, as I have a strong desire to ride!!!

Also, I overrode the ballast resistor (I think that is what it is called). You said that's necessary, right TC?

[randy]

Corey,

Follow T.C.'s advice. You have 3 ohm coils, so don't need the ballast resistor.

If you can't wait for new caps, take a look inside the plug end of the cap. That little brass connector may have a slot in it. if it does, you can unscrew the connector and the resistor will fall out. Many times there is corrosion in there. Clean it up and you should see a difference in the resistance reading. If not, ditch the resistor and substitute a cut piece of screw or rod the same size. You should have spark then.

The resistor is only there to reduce RF interference, it's not needed to make the spark.