78-79 E/F/SF Simplified Wiring

[Brian_D]

Sloooowly dissassembling my 79 F project bike for some slight modifications. Have gotten this far into the stock wiring and thought it may be helpful to others here - of course all the standard disclaimers for liability and errors apply




All checks were performed against a stock 78E wiring harness (thanks andreas) and a stock 79F bike. According to clymers, the same wiring is also on the 79SF. Feedback and corrections are welcome.

[kta]

I'll have to compare what I did to how you set up yours. I completely gutted the wiring on my project bike. The bike kick starts, there is a toggle for ignition power and a toggle for lights (headlight and brake). The toggles are under the seat. Everything else is gone. I'll check out what I actually did and compare my colors to yours.

[audijunky]

You Guys are nutz Seeing all that wiring hanging there makes me quezzy I plan on moving some switches from handle bars to frame somewhere, like the on/ off switch and starter button but I am thinking twice about it now. How long did it take you to unwrap and sort all thoses wires out?

[TomB]

78-79 E/F/SF Simplified Wiring

Nice one Brian

That'll help a lot. I'm making my own harness so I'll use this for a guide, the only difference is I'm using Honda CB900 ignition CDI's and pick ups.

I was going to try and get an original harness to alter but there is going to be so little left I couldn't see the point in the end.

Tom

[John]

One question

Looking at the diagram, it seems that you have the resistor wired up to be in use during the crank cycle, and not during the run cycle. The wire leading from the start soleniod should be supplying full battery voltage during cranking, and then once it's running, the resistor should be in the run circuit to drop the voltage to around 9v. Other than that, nice work.

[Brian_D]

John, thanks for the heads up. Will double check that part of the oe harness this weekend and confirm. Think that was BEFORE I got my $2 reading glasses

[John]

Maybe you need the $5 reading glasses. Or maybe even the glasses with the funny lines running across the lens...like mine.

[Brian_D]

Eye doctor had perscribed those funny glasses with the lines over a year ago (never got it filled). Now he wants me to go in every year for an annual eye exam - ha. If he was a real doctor, I wouldn't need glasses - or an annual checkup.

[TopCatGr58]

Great work Brian,

Originally posted by Brian_D
Eye doctor had perscribed those funny glasses with the lines over a year ago (never got it filled). Now he wants me to go in every year for an annual eye exam - ha. If he was a real doctor, I wouldn't need glasses - or an annual checkup.

Careful, them's fighting words! There are 2 ophthalmic techs here on the Forum!

IF you're over 35 y/o, it's recommended to have an eye check for at least to check your Intraocular Pressure to rule out glaucoma.

If there is any family history of it, or other eye diseases ie. macular degeneration, diabetes, it's even more important to get yearly checks. Many of these diseases can cause lots of damage before they affect your actual vision, and then it can be too late!

But if you are otherwise healthy, then we commonly allow folks 2 year intervals. Ain't growing "up" fun?!
T.C.

[79XS11F]

I plan to replace my wiring harness .. on both bikes ... as they came from the factory. It is the next thing on my list. I will do both while the frame for the restored bike is out for painting
Rob

[Brian_D]

hypothesis ....

Originally posted by John
Looking at the diagram, it seems that you have the resistor wired up to be in use during the crank cycle, and not during the run cycle. The wire leading from the start soleniod should be supplying full battery voltage during cranking, and then once it's running, the resistor should be in the run circuit to drop the voltage to around 9v. Other than that, nice work.

checked and rechecked the stock '79F wiring harness with a dvm and still can't find a mistake - which brings me to the following hypothesis ....

PARTIAL voltage is supplied to the coils (thru the ballast resistor) during BOTH the crank and run cycles; when the TCI senses cranking voltage on the R/Y input, it switches FULL voltage to the coils on the W/R output.

Feedback and corrections are welcome.

[Brian_D]

Re: 78-79 E/F/SF Simplified Wiring

Originally posted by TomB
.... the only difference is I'm using Honda CB900 ignition CDI's and pick ups.

Tom, can you enlighten me some more on the CB900 coils and pickups? I've read some of the info referring the coils on the UK site but missed the references to the pickups. Can the pickups be used on ANY year XS or only with the 4R0 TCI?

[TomB]

Brian

I'm using CB900 pick ups at the crank which are physically nearly identical to the XS pick ups, and I'm using CB900 CDI's (two, one for each coil) to trigger the ignition, so no Yamaha ignition components at all. Coils can be any coil that doesn't use a ballast resistor, I've got some CB550 Honda coils spare so I'll use them.


Here are a XS set of pick ups (left) which I will remove and replace with the Honda pick ups (right) The CDI's are above with red leads, the coin sat on top was just to give some of the UK lads an idea of size, probably not relevant to you lads
The CDI's are a lot smaller than the XS TCI, I'm mounting them under the gas tank next to the rec/reg with a small home made bracket. The CB550 coils I think will fit the XS frame brackets, maybe a small alteration.


I've had this set up firing on the bench from a battery and ran a steel screw driver across the pick ups, got a huge spark.

Tom

[Brian_D]

Cool. I'm definitely interested in following your progress on this. May be just the ticket for my '79F project (read years in making).

[TomB]

Following my progress????

I hope you're a patient bloke, I'm still welding up the frame and monoshock conversion.

I'll definitely keep you informed or keep an eye on progress here