Stuttering while accelerating?

[Graman]

Thanks Motoman. How would you suggest making these measurements. I wouldn't of thought there would be any voltage at the coils unless the bike was running or at least cranking over. If running the voltage would be pulsing a couple of thousand times a minute. I'm not sure how my digital multi meter would react to that but I do have an older analog meter that might work better in this case.

[motoman]

Thanks Motoman. How would you suggest making these measurements. I wouldn't of thought there would be any voltage at the coils unless the bike was running or at least cranking over. If running the voltage would be pulsing a couple of thousand times a minute. I'm not sure how my digital multi meter would react to that but I do have an older analog meter that might work better in this case.

Talking voltage TO coils(primary ignition), not voltage to plugs(secondary ignition).

[TopCatGr58]

In otherwords, turn key on and check red/white wires voltages. During starting mode...the TCI bypasses the Ballast resistor and sends 12V to the coils for easier starting action, so you should see similar battery level voltage at the coils with just the key on. During running, you should see the voltage drop to about 9 volts due to routing thru the ballast resistor before going to the red/white input voltage/power wires/primary voltage leads....and you should be able to measure this also while running without any problems with pulsing affect.

T.C.

[3Phase]

Hey, Graman,

If it was 'good' (fast) enough to notice the ignition pulses, the digital meter might keep changing the least-significant-digits on the display but most will pretty much ignore it because they effectively can't 'see' the pulses.

When you installed the 3 Ohm coils did you bypass/remove the stock 1.5 Ohm Ignition Ballast Resistor? If you didn't by bypass the resistor you're running ~4.5 Ohm coils.

If you did bypass the resistor but the connectors are loose or dirty you've got an intermittent coil primary voltage supply problem.

Bypassing the resistor also removes the Start bypass feature when cranking the engine because there is no resistor to bypass.

You will have to remove the fuel tank to measure the voltage at the coils.
Red/White wire: V+ from 10A Ignition fuse
Orange wire: #1 and #4 V- to the TCI
Gray wire: #2 and #3 V- to the TCI

The TCI is supposed to shut itself off after a few seconds if the engine isn't turning over so it doesn't burn out the coils and transistors or run down the battery. Press the Start button and watch the voltage at the coil primaries.


Roughly the same type of thing will happen if, for whatever reason, the charging system isn't keeping the system voltage up. The TCI will start to stumble and fall over on it's pointy little transistorized head.

.

[motoman]

In otherwords, turn key on and check red/white wires voltages. During starting mode...the TCI bypasses the Ballast resistor and sends 12V to the coils for easier starting action, so you should see similar battery level voltage at the coils with just the key on. During running, you should see the voltage drop to about 9 volts due to routing thru the ballast resistor before going to the red/white input voltage/power wires/primary voltage leads....and you should be able to measure this also while running without any problems with pulsing affect.

T.C.

Thanks T.C........knew I could count on you or a couple others for more detailed correct enlightenment! I just get lazy, and try to start the initial trouble shooting procedure.

[3Phase]

Just a quick note about the Start circuit and the stock Ignition Ballast Resistor bypass feature when the resistor has been removed or bypassed for aftermarket 3 Ohm coils:

The Start circuit resistor bypass feature doesn't just bypass the Ignition Ballast Resistor during engine cranking, it also bypasses the killswitch and the 10A Ignition fuse but the current and voltage that can be fed to the rest of the Ignition circuit is limited by the 1.5 Ohm resistor.

Normally during engine cranking, 12v is shunted up to the TCI with the Green wire on Starter terminal of the starter solenoid.

The TCI sends that 12v through a White/Red wire over to the V+ side of the Ignition Coils but after the ballast resistor so the coils will get full battery voltage during engine cranking.

When the Ignition Ballast Resistor has been removed or bypassed, the amount of current that can be supplied to the entire Ignition circuit during engine cranking is only limited by the size of the Green wire on the starter solenoid and the White/Red wire from the TCI to the coil V+ connector.

Usually that's not a problem when everything is copacetic and the new 3 Ohm coils will live happily ever after. If something goes worng then the entire Ignition circuit becomes a fusible link.

.

[Graman]

Thanks guys. Your a wealth of knowledge.

I did bypass the ballast resistor when I installed the 3 ohm coils. I will make these measurements tomorrow if I can and post the results. Friends not home today or I would be doing it today. I did check the connections to the coils a couple of months ago when I replaced the plug wires and they looked good but I will check them again.
Good news on the valve job. I talked to my friend earlier and he said he wouldn't mind if I left my bike in his garage for a few days while the shims were ordered in. Great. We will only have to take it apart once.

P.S. I had another friend I ride with who owns a 2006 Harley Road King drop by when I was testing my pickup wires the other day. He told me I should of bought a Harley so I wouldn't have to be working on my bike all the time. I laughed at him and told him that my bike is already 36 years old and that I will probably still be riding it when his Harley is in the scrap yard. He has already spent more taking his Harley into the dealer for a variety of problems than I have spent on buying my XS1100 and all of the mods and repairs that I have done 3 times over. Not including the $16,000 he paid for it used. Just another brain washed Harley owner.

[3Phase]

Tell your friend he's got a lot to look forward to because ninety-percent of all Harleys ever made are still somewhere out on the road today -- the other ten-percent made it home safely!

.

[Graman]

Tell your friend he's got a lot to look forward to because ninety-percent of all Harleys ever made are still somewhere out on the road today -- the other ten-percent made it home safely!

.

Good one. Gonna have to use this one next time he comes around.

[TopCatGr58]

Just a quick note about the Start circuit and the stock Ignition Ballast Resistor bypass feature when the resistor has been removed or bypassed for aftermarket 3 Ohm coils:

The Start circuit resistor bypass feature doesn't just bypass the Ignition Ballast Resistor during engine cranking, it also bypasses the killswitch and the 10A Ignition fuse but the current and voltage that can be fed to the rest of the Ignition circuit is limited by the 1.5 Ohm resistor.

Normally during engine cranking, 12v is shunted up to the TCI with the Green wire on Starter terminal of the starter solenoid.

The TCI sends that 12v through a White/Red wire over to the V+ side of the Ignition Coils but after the ballast resistor so the coils will get full battery voltage during engine cranking.

When the Ignition Ballast Resistor has been removed or bypassed, the amount of current that can be supplied to the entire Ignition circuit during engine cranking is only limited by the size of the Green wire on the starter solenoid and the White/Red wire from the TCI to the coil V+ connector.

Usually that's not a problem when everything is copacetic and the new 3 Ohm coils will live happily ever after. If something goes wrong then the entire Ignition circuit becomes a fusible link.

.

Hey Scott,

I reviewed the the wiring diagram for the 79Sf, as well as the 80 G that you provided in great detail/color....above you stated "GREEN" wire?

I thought it was the Red/Yellow wire that comes off of the starter relay to the TCI, and the RED/WHITE from the TCI that is energized to bypass the B.R. during the start process.

The Blue/White wire on the starter solenoid is of course the negative ground trigger/actuating wire....that's the closest to GREEN for it. Not trying to nitpick or point fingers regarding a possible description error, just didn't want to have him looking for the wrong wire.

As far as the circuit NOT having a fuse, would you suggest we put a fuse inline with the Red/Yellow wire going to the TCI to provide the protection against a SHORT that could otherwise fry the TCI??

T.C.

[LoHo]

Don't feel bad; the first time I really got on the throttle, I stuttered for about a week.

[3Phase]

Green to Red/Yellow

Larry! LMAO! I know that feeling!

T.C., I know my '80G_US schematic shows it but I'll have to check the '79SF harness hanging on the wall of the garage. I'm pretty sure it has a fat Green wire on the same solenoid terminal as the Black wire for the Starter too, like the '80G.

<Jeopardy music>
....
</Jeopardy music>

Yep. I haven't checked my '79F but the Green wires on my '79SF and '80G are relatively short. You are absolutely correct about the Red/Yellow wire that actually runs up and into the TCI. I forgot about that and there's a bullet connector where the Green and the Red/Yellow wires join that's run under the edge of the seat pan next to the plastic inner fender.

Randy would probably know this off the top of his head without pulling apart a TCI but I think there's a diode inside the TCI between the pins for the Red/Yellow 12v IN and the White/Red 12v OUT. The diode keeps the resistor bypass circuit from backfeeding current into the Starter motor once the engine is running.

A fuse would be a good thing for a true belt-and-suspenders setup but it's not strictly necessary as long as you remember the Ignition circuit is not fused when you're cranking the engine.

.

[motoman]

Interesting........only way I ever knew how to check voltage spike peak being in spec. at plug was using the 'old school' Sun diagnostics roll-around cabinet machine having the ociloscope, which showed a potential problem BEFORE it was noticed 'seat of the pants' operating vehicle.

[3Phase]

I wish I had one of those old Sun machines but assuming it worked and was still relatively in tune, the display would probably be all gassy and getting dim.

There are modules that you hook up to the engine and use your computer like a handy-dandy Sun machine with even more capabilities but, uh, I refuse to hook up anything with fifteen to fifty-thousand volts on it or more to my computer.

Of course I'd be fine with using one with any computer that isn't mine! I'm just saying, you, know?

.

[CaptonZap]

I wish I had one of those old Sun machines but assuming it worked and was still relatively in tune, the display would probably be all gassy and getting dim.

There are modules that you hook up to the engine and use your computer like a handy-dandy Sun machine with even more capabilities but, uh, I refuse to hook up anything with fifteen to fifty-thousand volts on it or more to my computer.

Of course I'd be fine with using one with any computer that isn't mine! I'm just saying, you, know?

.

http://http://stuccu.com/s/Dso+Nano+...02efd&device=c
Wrap a three inch long piece of wire around the plug lead, hook the Oscope lead to the wire, the scope to ground, and let induction coupling be your friend.
No high voltages involved, unless your plug leads have leaks, and a spray bottle with water on a dark night will answer that question.

CZ