Franken Electrical Issues

[Gallaecus]

I started building a bike from a box.

the frame is 4RO "81 Special"
the engine is 3H5 "80 Standard"
the wire harness is 78-79 Standard"

79 carbs, 2h7 tci. 79 reg/rec

I got it to run pretty well but when it came to the lighting system....things went not so well...

First was the problem with the directionals. what i ended up doing was....not using the blue wires in the front and I tapped into the ground for the rear signals. using special turn signals. they seem to work 95 percent of the time now but sometimes one side wont flash.

now for the headlight. sometimes it worked sometimes it didnt. and went hand in hand with the tach. the standard had a switch on the right control for the lights. i have a later control without the switch so I put a switch in between the blue/black and red/yellow.

before this I was relying on the headlight relay. and it was working and so was the tach.... when it stopped working....the HI LO switch would send the tach to 5k.... hi 5k lo 0... the engine was not running... I am not making this up...

So thats when i put the headlight switch in. and it gave me a headlight, but did not fix the tach.... the tach stays at zero when idling but with the switch on it seems to read correctly with the throttle, but drops to zero without throttle. with the switch OFF...the tach will jump to 5k with a hard blip of the throttle.

I have plugged and played different modules quite a few times, so i need to regroup, start over and document this here in a thread.

Not sure if it is related, but when riding the bike.....hard acceleration will cause stumble or a cut out. seems to be at higher speeds in higher gears, but that last quarter turn of the throttle causes a cut out. I have pulled on the pick up wires to no effect. swapped tci, reg, headlight relay, flasher relay, cleaned contacts and more.... so thats my story...thanks for listening.

[Gallaecus]

[Gallaecus]

can I use 78-79 harness on an 80 engine ? on the 80 schematic it is showing a diode in the field on the white wire from reg to relay.

Im assuming i have by passed the relay with the switch installed, but the tach still doesnt function. i have replaced the fuse block. the schematic only show tach lights. what drives the tach and from where? am i looking for an intermittent broken wire shared by head light and tach ?

[Gallaecus]

any Electrical Gurus out there ?

[bikerphil]

The tach gets it's signal from the one of the alternator legs (AC voltage).

The headlight relay is also triggered by the alternator, the yellow wire is used on the 78-79 models and the white wire with the diode triggers the relay on the 80-81 models.

The headlight relay may be bypassed by unplugging it and jumping the red/yel and the blu/blk in the harness plugs.

The 78-79 uses a different headlight relay (internal diode) than the 80-81 (external diode).

The reserve lighting unit (RLU) may be bypassed by unplugging unit and connect blu/blk and blu/yel together at the harness plug.

[Gallaecus]

thanks Phil.
should I leave the headlight relay out. and jump the wires, or jump it on the back side of the connector and leave the relay in there?

do I need to by pass the RLU ?

I will try that tomorrow, thanks

[bikerphil]

Unplug the relay and make a jumper wire with two male spade connectors to connect in the plug of the harness. In other words, take it out.

Bypassing the RLU just simplifies everything for the time being. Try it both ways.

[DGXSER]

If I am reading correctly, I think Phil is saying the harness you have does not have a diode in it. So, if you have an 80-81 relay it also has no diode in it. So the two will not work and play well together. Choice is to bypass the relay, or add the diode into the harness wiring. Or get a 78-79 relay.

The RLU is IMO kind of like the OCTY, it is extraneous and suspenders with your belt. To simplify your headlight system I would bypass it since it may be part of your problems. I bypassed mine a while ago when I installed an HID headlight. Did just as phil suggested, made a jumper wire for the said wires, packed the other ends in the connector with dielectric grease and wrapped in e-tape to keep down on corrosion issues.

[Gallaecus]

looking at the diagrams in ch 7, I think I have already by passed the relay and have jump L/B and R/Y with the switch from the connector to Right hand controls. I have the head light working, but not the tach. they worked for a while and went together. I will try what phil said and also just removing relay. the schematic for 78 79 does not show the tach, only tach lights. and that white wire from the reg that should have a diode in it and trigger relay now goes to my fuel gauge which does work cuz its a special tank with a standard gas gauge. and that yellow wire which exists in my harness but not in my alternator still baffles me as to how the relay did work for a day. Im thinking I should just get the right harness.

[ManagerMike]

Check the charging system per the manual, it provides the tach signal as well as the latching signal for the headlight relay. That they both went together strongly suggests a common problem, and the one thing they both have in common is the charging system.
Good luck, Mike.

[Gallaecus]

I am considering using this harness from an 80 81 special.
but I need to know if this is compatible with the 80 standard engine 3h5
the wire harness does not match the schematics color code for
the TCI or the number of wires to TCI.
would I use the 2h7 or 4r0 tci
and the pick up coil problem i am having is starting to make sense.
in addition to the headlight and tach correlation to alternator.

[DGXSER]

That harness is for an 81 special. For the most part, very interchangeable with the 80 engine. However, the 4RO TCI is a one year specific to the 81. If you use the 4RO TCI you need the timing setup for the 81 which does not have mechanical advance.

[Gallaecus]

thx Don.

you are correct.. apparently a 78 79 harness does not play well with an 80 81 motor. my bad.

here is more info offered up by Crazy Steve ... thx

http://www.xs11.com/forum/showthread.php?t=35337