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1979 GS750E did right

32K views 111 replies 21 participants last post by  woodsman 
#1 ·
so now that I have the GS in my garage, I can finally start ordering the things I need for it. The PO used if for track days, but due to a TBI from an accident (presumably on a different bike...) can no longer ride. My plan is to catch up on basic maintenance for it, do some suspension improvements and get it on the road. I still need to get a safety wire tool to wire everything down once its all assembled again.

As a side note... I know it may be douchey, but I'm seriously considering leaving the number plates on for the street.

Right now I have the following ordered:
-clymer manual
-Progressive front and rear suspension
-rear caliper rebuild kit
-front fork seals
-all balls wheel bearings
-all balls steering stem bearings

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The rear caliper was "sticky" and after taking it apart, one of the pistons was frozen, and the master cylinder had seen better days (there was actually a plastic o-ring lodged in the hole of the banjo bolt... weird). Luckily, the PO had two other rear calipers in various states that he gave me so I took all three and disassembled and cleaned them in order to put together one good one. A grease gun is the absolute easiest way to undo a stuck caliper!

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So right now, I have three serviceable rear calipers, two good pistons, and one good master cylinder. All that's left is for the rebuild kit to arrive and to get it all put together. Later on I'll upgrade the rear to braided lines.

The next issue was the leaky petcock. The PO had switched from a vacuum one to standard, and had made his own bracket for it. After taking the petcock off the tank and cleaning away the paper gasket and rubber cement gasket I found why it was leaking (other than shitty gasket materials).

Seems that there's a dent in the side of the opening that was a little too much for the rubber sealer to handle. In the next couple days I'll sand the area down and hit it with a coat of JB weld to level it all out, then get a strip of rubber to use as a gasket. This ought to do until I get the second tank cleaned out and painted up.
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Here's the petcock assembly... I've added some O-rings to the screws to hold them on for now. When the petcock is attached to the tank, the O-rings will seat in the recesses on the tank (like stock).

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And at the end of the day (but it still runs with fuel in the carbs):

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#3 ·
You have got the makings for a very nice vintage superbike. The one glaring issue for me is that hideous seat. It also looks like the rear cowl sits too far back behind the rear edge of the rear wheel. I would shorten the whole thin until the end of the seat cowl is even with the back edge of the rear tire. Then reupholster the shortened seat pan to look right with the tank and rear cowl. The yellow with black number plates are novice colors for club racing. If you are going to run number plates then do it with white plates and a black 34 on them. Google images will give you some ideas.

Ken
 
#5 ·
Thanks for the advice.

The seat is the stock setup, just the pan has been reupholstered... Ill see if it needs adjustment after riding it a bit.
 
#6 ·
There's a recess in the tank for the o-rings. The rubber gasket will cover the whole aluminum plate and the whole thing should sit flush. That said, yes, I am going to replace the whole thing... Probably with a pingel set up.
 
#14 ·
As an aside, it's really annoying dealing with thegsresources and how they're migrating their web site. Using internet archives to look up stuff on the site from 2013 gets old quick. That said, a ton of the stuff there is (obviously) geared towards the GS1000.
 
#16 ·
I say leave the seat. The original yosh gs1000 had a seat like that and that is probably why the po had that one done. On the GS the tail is bolted to the frame section so it is difficult to move it around without modding the frame rails. I mean the bike is already cut in another place so if you wanted to I don't see the harm in doing it since it will never be stock anyway, but I also don't really see the benefit as it is a lot of work to do properly.

Instead i would suggest swapping out the stock brake and tail for something that sits more flush with the cowl. Maybe LED. This will also help sell the faux race bike look as the original ran without lights.

If you want to run the plates either keep the ones you have or get copies of the originals off the yoshimura/ Wes Cooley bike.
 
#21 ·
No worries. Are you planning on using that tap you put the pic up of?

Looks a little primitive is all. Is there a vac port on your carbs? My early (kickstart equipped) gs 750 parts manual shows a vac diaphragm tap but this somewhat clearer pic from my gs thou shop manual gives you a manual on off type like that which you have now.



options are there and unless you start making a shitload more power from the mill than it likely pumps now, i doubt you'll drain the bowls via lack of flow rate from the standard types in a hurry. Higher (sustained too) high speed touring on my 81 gsx1100 has never shown up a propensity of the tap to starve and thouh not race spec, when the chocks are pulled the big girl does slake her thirst pretty hard.

i like the fibre type washers personally, copper doesn't appreciate reuse and aluminium less so.
 
#23 ·
I guess this raises the question, is there some huge benefit of a vacuum petcock vs standard?
 
#29 ·
Productive Week:

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Got progressive front and rears, fork seals, front and rear all balls wheel bearings, all balls steering stem bearings, fuel filter and some other minor things.

Rebuilt the rear caliper and master cylinder, fixed the leaky petcock, and repaired the headlight switch a few days ago.

did the forks today...

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By the looks of the dust boots, the rusty mess that used to be the retaining ring, and the seals that were frozen solid to the forks, as well as the grey ooze that was fork oil, I don't think this has been serviced in a while. I went with 20wt oil and preloaded the springs 1/2" to start. Ordered new retaining rings and dust boots today too, so those should be here some time this week.
As soon as those come in I'll be able to button up the front end.

After that I just need to install the rear wheel bearing and she'll be rolling again.

Things to do this week:
-Change the oil
-Change front and rear brake fluids
-Safety wire everything back down

One question: the bike came with a steering damper. the mounts were on the left fork leg, just below the bottom triple as well as on the frame tube. I installed the damper to the mounts and the damper reaches its end before the tree hits the steering stops (and yes I tried adjusting the damper). Is this how it's supposed to work or do I need a longer damper?
 
#30 ·
One question: the bike came with a steering damper. the mounts were on the left fork leg, just below the bottom triple as well as on the frame tube. I installed the damper to the mounts and the damper reaches its end before the tree hits the steering stops (and yes I tried adjusting the damper). Is this how it's supposed to work or do I need a longer damper?
Throw up some pics. I'd imagine there would be some way to mount it so it doesn't hit the stops on the damper (maybe spin the clamp on the fork leg?).
 
#32 ·
Some progress in the past two weeks...

got the dust boots and retaining circlips in so I was able to get the front end mounted. After mounting up the handlebars and grabbing the brake lever, I noticed there was no resistance... strange because they were working ok before I took the bars off the triple tree. popped off the reservoir cover and saw there was no fluid in it. No worries, I was going to flush them anyways. (These front brakes could use a rebuild as all the rubber bits are pretty sad but I'll do it after putting a few mile on the bike). Anyways, I was graced with this sight when flushing the system:

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gross.

Went ahead and added fluid to the newly rebuild rear caliper and master cylinder. Went easily enough, but after bleeding them pretty thoroughly it still drags a little bit, so I'll have to do a little troubleshooting on that.

Other than that, I got everything torqued down and just need to begin safety-wiring all the bolts that were taken off.
I received the title in my name the other day, and I was planning on registering it historically (bike as i bought it didn't have blinkers or a horn so registering it historically wouldn't require an inspection) but since I have the horn and blinkers and it will only take me an hour or two at most to get everything wired I'll likely just get it inspected and registered normally.

Just need a few more good hours on it and I'll be on the road (once a good rain storm washes most of the sand off the roads here in MO).
 
#33 ·
And we have blinkers.
Since the left side controls were completely fucked, I've butchered the box so that I could fit generic buttons and switches into it (until I feel like buying a new one). As you can see, I have on-off for the light (hi-beams only for now... daytime runner anyway), on-off-on for the blinkers, and an interrupter button for the horn (to be installed tomorrow-ish).

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Here you can see my hood-rat wiring job. Everything works and is secure, so what more could you want. Also, you can see my chopped up gauge brackets. Somewhere along the life of the bike, the wires for the gauges were cut really short. Rather than having that monstrous dash sitting there useless, I pulled the gauges out of it and plasti-dipped the orange buckets black. I cut the bracket in two so I can bring the gauges in closer to each other. A case of form over function perhaps, but I don't really care. Eventually I'll wire the gauge lights into the headlight switch.

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Also, I've figured out why the PO had the steering damper the way it was (stopping the tree before it hit the steering stops). Because of the bars and the after market throttle, the steering stops allow the throttle cable elbow to hit the tank. something else to add to the list.
 
#35 ·
I used ethanol resistant fuel tank repair "putty". I actually only needed a tiny bit to bring the dent up to a level where the rubber gasket would seal evenly.
 
#36 ·
Took the bike for a shake-down ride today... nothing fell off and nothing broke.
I did notice that the battery died after a bit, but I was able to kick start and continue (albeit with a dim headlight/tail light and no blinkers). I have the bike on the charger right now, but we may be looking at the common stator issue for these GS's.

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I did also figure out why I thought my rear caliper was sticking. Apparently there's now some interference between the rear brake stay and the rear tire...

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I'm not sure how that wound up happening... so if anyone has any suggestions, I'd appreciate the input!
 
#38 ·
Check your chain alignment. It is very difficult to certain from your photos, but it looks like the axle may be cocked. Maybe the chain adjuster on the left side wasn't tight?



...and most GS's are "free of charge", so to speak. Look into regulator and rectifier issues first. If the stator checks out, then a Shengdin SH775 rectifier is a good upgrade. (Polaris RZR 800) and Triumph Bonneville Harness.
 
#39 ·
Check your chain alignment. It is very difficult to certain from your photos, but it looks like the axle may be cocked. Maybe the chain adjuster on the left side wasn't tight?
Dingdingdingding!

Rear axle was cocked indeed. Just goes to show you, even when you've gone and taken your time with everything, go over things a third time so you don't die.

...and most GS's are "free of charge", so to speak. Look into regulator and rectifier issues first. If the stator checks out, then a Shengdin SH775 rectifier is a good upgrade. (Polaris RZR 800) and Triumph Bonneville Harness.
The electrical system as it stands is pretty jacked anyways... I'm going to go an re-do everything wiring-wise on this once my Z1 is back on the road.
 
#41 ·
some thread necromancy since we're on the GS750 train lately...

when we last left off, I had been running into the issue of the bike not charging and after doing some research and multimeter checks, I found the regulator/rectifier to be bad. I went ahead on the recommendation of thegsresources and installed a polaris RR, subsequently fixing the issue.

I took the time to adjust the valves and found them to be pretty far out of tolerance. I was able to swap a few of the shims around but wound up having to order 5 new ones. Hopefully all those years of losing tolerance haven't burned any of the valves too badly. I replaced the cam end plugs, cover gasket, and vacuum gasket? while I was in there too.

I also picked up a dyna ignition and coils (from here: Dyna s Electronic Ignition Coils Wires Suzuki GS550 GS750 GS850 550 750 850 ND | eBay) figuring that the original coils were one of the final things that were crapping out on the bike.

well I got them installed and everything timed with a timing light and then went on to sync the carbs. Go figure the 3/4 slides were sticking and the adjustment screws were completely fucked so I dropped $150 on ebay and picked up a second set of carbs for the bike. I cleaned them out, rejetted them, and had them synced in less than 5 minutes. The bike feels a million times better now, and starts 100x more easily. Lesson learned, don't just glance at the slides or adjustment screws when cleaning carbs.

Final step was to add a switch to the headlight bucket to give me hi/low beam option.
The bike is now registered and road legal.

I'll probably ride this bike for a few months and look at trading it for something neat in the spring... maybe a road-legal sandrail?
 
#43 ·
So after several trouble free years of riding, the hoodrat electrical system is finally giving me issues. Rather than try to fix the mess that myself and the previous owner created, I bought a used harness on eBay for $30 and spent another $20 on generic handlebar switches.

First up was to run the harness through the ultrasonic cleaner with a 50.50 mix of distilled water and Krud-kutter.



The water after:



Afterwards I rinsed the harness and sprayed all the connections with contact cleaner, then hung to dry.



Here's the switches:



Now I need to sit down with the wiring diagram and get these new switches set up.
 
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