4RO Ignition Unit

[MileHighXS]

Hi guys, I've been a long-time lurker on the board and finally got around to registering. My '81 XS1100LH is about ready for the road after nearly a year of part-time restoration work. When I bought it, it hadn't been run for at least 10 years. You can imagine how I felt when she fired up for the first time!

It would have been impossible to get this job done without the members of this forum so, to you all, an overdue thanks.

I can use some help with my 4RO ignition unit. I may have fried it tonight charging the battery. The bike when from quick-starting to not firing at all.

Is there a quick check I can do to isolate the unit as the problem?

Does anybody know where I can buy a good working replacement?

Any progress been made on repairing these boards on a component level?

Thanks, Mark

[randy]

Hey, Mark. Welcome.


That's quite a list of questions, but I'll try.

First, it's not likely that you fried your TCI by charging the battery, unless you reversed the +/- with the key in the on position, but that's not likely either, because that would discharge the battery.

The only way to truly isolate the TCI as your problem is to swap it with a known good one, but there are a few things you should do before that:

Have you gone through all of the connections from the TCI to the coils and from the TCI to the pickup wires? Don't miss the connector behind the fuse holder plate. You have to remove the plate to get to it. Clean 'em all up, then see what you get.

Then check the Ballast Resistor. I've heard that some 81 models did not have them, but I had one on my 81 Special. If it's open you won't get a spark except while cranking. This can be confusing, because when you crank, you'll get spark, then when you let go of the starter button, no spark, motor dies.

As far as TCI replacements, they come up on Ebay frequently. Just be sure to get a 4RO unit, because those have electronic advance on the board, unlike the earlier models (78,79,80) that have a mechanical advance unit under the timing plate.

I have had success repairing the 4RO units. If all else fails, as a last resort you can ship it to me and I'll go through it. Let me know and I'll send you my address.


Hope this helps. Keep us posted on your progress.

Randy

[MileHighXS]

Thanks for the quick response. I'll run some tests today and get back to you. I noticed in an earlier post, you mentioned replacing the 2 transistors in the TCI with Motorola 3055s. Will they work on this 4RO unit or is that for the earlier ones? MArk

[randy]

Mark,

The 3055's are in a TO-3 case and are for the earlier boxes, the 4RO uses a TO-220 case. If I were going to venture an eductaed guess, a good choice would be a TIP-41 transistor. It has similar characteristics to the 3055.

HTH Randy

[MileHighXS]

Hi Randy,

I ran tests on the ignition coils, pick-up coil wiring and TCI outputs to the coils. All checked okay but no fire.

Then I pulled the ignition unit, cleaned and re-soldered every connection, inspected and cleaned every related connector on the bike and finally cleaned and re-gapped the plugs.

I put everything back together and she started right up. I guess I found the problem (or problems) but couldn't tell you what it was! Maybe she just needed the attention.

Tomorrow I'll sync the carbs, set the idle and see if I've tamed her enough to ride her.

Thanks for the help. Best, Mark

[randy]

Mark,

90% of TCI problems are fixed by re-soldering the pins on the board. Most often the pins that connect to the sockets are the cuprits. For everyone out there, when you open the cover there is a double row of pins near the sockets. With a small soldering iron, re-heat and apply a small amount of 60/40 solder to each pin. Be careful not to use too much solder as to bridge between pins.

The rest of the troubles can usually be cleared by cleaning the rest of the connectors in the IGN system.

Looks like you did them all, so you won't have to worry about them for a while. When I re-built Swamp Thing I took apart every connector in the wiring harness and either cleaned or replaced all the pins. Then I applied a good copper grease to them. No wiring troubles yet.

Glad you found it.

Randy