1978 GS750 Wiring questions

[Kyle M.]

Hello all, this is my first post here and I have a lot of questions. I will start off with this one

I need a wiring diagram or someone who knows how to wire in the magneto to the rectifier. I have 3 wires coming from the magneto, do they all go to the rectifier? This is a custom set up on this bike. Then how about the regulator? I need a little help, thanks

[Steve]

First of all, BassCliff will be along shortly.

Now, for your wiring dilemma. Your bike has separate units for rectifier and regulator. It is possible to get a single unit that does the function of both. Member Duaneage usually has some for sale for $40. They are tested and proven good before he ships them, so you know you will be getting a good one.

If you wish to keep the stock setup, yes, all three yellow wires go to the rectifier. Then the output of the rectifier goes to the input of the regulator. The output of the regulator then goes to the battery and the rest of the bike.

.

[BassCliff]

Hee Haw Howdy!

Hi Mr. Kyle M.,

Let's see if this will answer a few of your questions. It's your mega-welcome!

Let it be known that on this day you are cordially and formally welcomed to the GSR Forum as a Junior Member in good standing with all the rights and privileges thereof. Further let it be known that your good standing can be improved with pictures (not you, your bike)!

Perhaps you've already seen these, but I like to remind all the new members. In addition to the carb rebuild series, I recommend visiting the In The Garage section via the GSR Homepage and check out the Stator Papers. There's also a lot of great information in the Old Q&A section. I have some documentation on my little BikeCliff website to help get you familiar with doing routine maintenance tasks (note that it is 850G-specific but many tasks are common to all GS bikes). Other "user contributed" informational sites include those of Mr. bwringer, Mr. tfb and Mr. robertbarr. And if your bike uses shims for valve adjustments, send an email to Mr. Steve requesting a copy of his Excel spreadsheet that helps you keep track of clearances, shim sizes and other service work.

These are some edited quotes from one of our dear beloved gurus, Mr. bwringer, with ideas on basic needs (depending on initial condition), parts, and accessories.
***********Quoted from Mr. bwringer************
Every GS850 (and most other models) has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting. It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years. It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

1. Intake O-rings (install NEW OEM or Viton only - common nitrile O-rings will quickly deteriorate from heat)
2. Intake Boots (install NEW -- these cannot be repaired)
3. Valve clearances (more important than most people think)
4. Carb/airbox boots
5. Airbox sealing
6. Air filter sealing
7. Petcock (install a NEW one)
8. On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)
9. On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.
10. Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.
***********************************
Carburetor maintenance:

Replace the intake boot o-rings, and possibly the intake boots. Here's the procedure:

http://bwringer.com/gs/intakeorings.html

Here's an overview of what happens with this particular problem:

http://cycleorings.com/intake.html

You'll also want to examine the boots between the carbs and the airbox. There's a good chance these are OK, but check them over.
And finally, if things still aren't exactly right, you'll want to order a set of o-rings for BS carbs from the GS owner's best friend, Robert Barr:

http://cycleorings.com

Once you receive these rare rings of delight, then you'll want to thoroughly clean and rebuild your carburetors. Here are step-by-step instructions that make this simple:

http://thegsresources.com/gs_carbrebuild.htm

***************************************
OEM Parts/Online Fiches:

I would definitely double and triple the recommendations to use Cycle Recycle II and Z1 Enterprises as much as possible. These guys are priceless resources. Z1 tends to have slightly better prices, CRC2 has a wider range of goodies available. If you're near Indy and can bring in an old part to match, CRC2 has a vast inventory of used parts.
http://denniskirk.com - Put in your bike model and see what they have.
http://oldbikebarn.com - seems to be slowly regaining a decent reputation, but it's still caveat emptor. They don't have anything you can't get elsewhere at a better price anyway.
http://www.babbittsonline.com/ - Decent parts prices. Spendy shipping. Don't give you part numbers at all. Useful cross-reference if you obtain a part number elsewhere. Efficient service.
http://bikebandit.com - Fastest. Middlin' prices. Uses their own parts numbering system to obfuscate price comparisons -- can be very confusing for large orders. Cheapest shipping, so total cost usually isn't too bad.
http://flatoutmotorcycles.com - Slow. Cheapest parts prices, crazy shipping costs. Don't expect progress updates or much communication. Real Suzuki part numbers.
http://alpha-sports.com - Exorbitant parts prices. Different type of fiche interface that's quite useful at times, especially with superceded part numbers. Real parts numbers. Shipping cost and speed unknown due to insane, unholy pricing.

Stainless Bolts, Viton o-rings, metric taps, dies, assorted hard-to-find supplies and materials, etc:

http://mcmaster.com - Fast, cheap shipping, good prices. No order minimum, but many items like bolts come in packs of 25 or 50. Excellent resource.
http://motorcycleseatcovers.com - Great quality, perfect fit (on original seat foam), and available for pretty much every bike ever made. Avoid the textured vinyl -- it's perforated.
http://newenough.com - You DO have riding gear, don't you? Great clearances, always outstanding prices and impeccable service.
***************End Quote**********************
Additional parts/info links:

GSR Forum member Mr. duaneage has great used upgraded Honda regulator/rectifiers for our bikes. Send him a PM.
New electrical parts:
http://stores.ebay.com/RMSTATOR or http://www.rmstator.com/

http://www.ricksmotorsportelectrics.com/index.php

http://www.electrosport.com/

For valve cover and breather cover gaskets, I recommend Real Gaskets (reusable silicon):

http://www.realgaskets.com

Carolina Cycle

http://www.carolinacycle.com

Ron Ayers Motorsports

http://www.ronayers.com

MR Cycles

http://www.mrcycles.com

Moto Grid

http://www.motogrid.com

Salvage/Used

http://www.ricepaddymotorcycles.com

http://www.ozpowersports.com/

If all else fails, try this:

http://www.used-motorcycle-parts.org/

Used bike buying checklists:

http://www.amadirectlink.com/roadride/Riderresc/checklist.asp

http://www.clarity.net/~adam/buying-bike.html

Lots of good info/pictures here:

http://www.suzukicycles.org

http://www.cyclechaos.com/wiki/Motorcycle_Wiki

http://www.bikepics.com
Basic motorcycle maintenance/repair:
http://www.dansmc.com/mc_repaircourse.htm
Online Clymer manuals:
http://search.ebscohost.com/ Click on "Small Engine Repair" then "Motorcycles". User=library, password=library. Note: This link may not work if you are on a school campus.

Thanks for joining us. Keep us informed of your progress. There's lots of good folk with good experience here.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

Click here to go to BikeCliff's website.

[Kyle M.]

First of all, BassCliff will be along shortly.

Now, for your wiring dilemma. Your bike has separate units for rectifier and regulator. It is possible to get a single unit that does the function of both. Member Duaneage usually has some for sale for $40. They are tested and proven good before he ships them, so you know you will be getting a good one.

If you wish to keep the stock setup, yes, all three yellow wires go to the rectifier. Then the output of the rectifier goes to the input of the regulator. The output of the regulator then goes to the battery and the rest of the bike.

.

What is the benefit to doing that?

As far as the wiring, the regulator only has 2 wires, a yellow which is the input and a black/white, which is a ground, no output. After I posted this, I went and downloaded a shop manual and got things figured out basically. Well worth the $9 IMO

Another question, will these bikes run without a battery?

[tomm]

The benefit is a more robust charging system. The stock setup has the regulator regulating one of the three stator outputs. The yellow stator output wire goes to both the regulator and one of the rectifier bridges. Another one is unregulated and always connected to another of the rectifier bridges, and the third is unregulated but only connected to a rectifier bridge when the headlight switch is on. The replacement setup eliminates the headlight circuit and regulates the full rectifier output instead of one of the rectifier inputs.

And no, you should not run without a battery.