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1979 GS 750L resurrect

  • Thread starter Thread starter Crake
  • Start date Start date
C

Crake

Guest
I figured I better put this info under a more appropriate forum. I've posted a number of pics under the new owners thread and intend to keep them coming as the bike progresses...

So to summarize, I picked up a '79 GS 750L from a fellow east of Regina, SK. This bike's original owner passed away in the 80's and the bike has largely sat, ever since, with the original 5K kilometers on the odometer. The PO (a friend of the original owner) used to store it indoors but lately pulled it out into his yard in hopes of selling it. He wanted $600.

The bike rolled easily in neutral however the pistons were naturally frozen. By and large, the bike looked in pretty good shape for 30+ years of storage.
 
Week 1 + 2

Week 1 + 2

Shortly after getting the bike home, I pulled the spark plugs and blasted all the pistons with a can of Fluid Film. Closed them up and took off for Christmas holidays.

Upon getting home, I pulled the tank, seat, airbox, and carbs. By the end of Week 2 I had the pistons rotating after putting a wrench to the crankshaft.

The air filter was completely disintegrated so I pulled it out and hosed out the air box. New filter ordered from the US.

Pulled apart the carbs. 30 years of old gas had left quite a mess in the bowls. I was originally hoping to clean the carbs as a unit but after seeing the jets, into the solvent they went...
 
There is a VM rebuild guide on BassCliff's site if you do not have it already.
 
Week 3

Week 3

After a few days soak, I was able to completely disassemble the carbs without damage. The carb slides were glued in place - a gentle warming with the heat gun eventually released them. I scrubbed the carb bodies down good and back into the solvent for a second bath. Each needle and jet was given a good cleaning and back into solvent for another week. I couldn't get the gaskets off without ripping them. New gaskets ordered from the US.

While waiting for the carb parts to arrive, I tackled a few more odds and ends. I cleaned up and painted the battery box and airbox, repaired the broken tach cable, scrubbed some rust off the various chrome trim, and took apart the gas tank. It was thoroughly rusted inside. I tumbled some bolts and nuts inside the tank to loosen most of the rust and cleaned off the sending unit (which was encased in about 3mm of rust). I'm pretty sure the bottom 1/4 of the tank was some sort of rusty petroleum slime for the first 10 years of the bike's storage. There was even a high-level mark on the sending unit float etched in the rust coat....
 
Week 4

Week 4

I have resolved to tackle one small project, every day, until my carb parts come...

The rear tire was dragging - I was initially worried about drive train issues but it was just a sticky rear brake caliper (duh). Disassembled and cleaned the caliper with my 6 year old daughter. She wanted to get her hands dirty... Changed the brake fluid in the rear master cylinder and the rear brakes are working good.

The front master cylinder, on the other hand, is gonna need a rebuild. The fluid was pretty much evaporated and reduced to a crumbly residue. I stripped the cylinder and cleaned out the internals, however on reassembly the plunger didn't want to slide easily. I suspect the spring has lost a lot of compression - it was pretty rusted - and the rubber cups were pretty hardened. I'll look at ordering a new cup and piston set once I get my next allowance.

Air filter arrived this week. Air box looks much nicer with a coat of flat black paint.

I disassembled the petcock - fortunately, only the intake ports were plugged with crud. The rest of the parts were clean and servicable. The rubber diapraghm was a little brittle, but I soaked it in oil and gently worked it back and forth until it flexed easily. After I got all the twigs and berries cleaned, I reassembled it and crossed my fingers. The vacuum action seems to work, and the internal o-ring valve seals nicely. With any luck I won't need a rebuild kit (or new petcock).

Today I experimented with electrolysis - This weekend I'm gonna drop in an anode in the tank and see if I can lift some of the rust out.
 
Doing small projects like that is an excellent idea. You should also go through the wiring harness, checking and cleaning the connectors with DeOxit.
 
koolaid_kid said:
Doing small projects like that is an excellent idea. You should also go through the wiring harness, checking and cleaning the connectors with DeOxit.
Click to expand...
Yep, electrical is gonna be my focus soon. I haven't put any voltage to the harness yet, not sure if there's any gremlins to chase out before attempting a test start. Fingers x...
 
Yeah, good deal. Pay special attention for melted multiwire connectors, blackened/melted wires, etc. Look at the color of the stator, it should be a nice light tan color, not dark and no dark spots, and start considering replacing the regulator with a quality unit, such as the Polaris.
 
Tank electrolysis

Tank electrolysis

Started electrolysis on the tank last night. For an anode, I suspended a thick steel bolt in a chunk of capped and drilled PVC pipe, but It didn't go very deep into the tank. And the petcock/sending unit hole keep leaking water no matter how I plugged them. After flooding my workbench and wasting about two hours trying to plug leaks, I decided to submerge the entire tank in a plastic tub and hang the anode outside the tank. There's a lot of scratches and pitting on the outside of the tank so I'm gonna strip the tank anyway... I might as well de-rust the outside of the tank at the same time.
 
...

...

Onward and upward... had a productive couple days. Got the carb gaskets in the mail while I was out of town on training. Spent last night reassembling the carbs with new gaskets and O-rings (the VM carb rebuild manual was priceless) and did a manual synch on the carbs. Got the carbs and airbox with new air filter remounted on the bike with a surprisingly minimal amount of cursing and swearing. In retrospect it was very easy getting them back on. My buddy's 450 was a bit more difficult, as I recall...

I have the old fuel tees (no O-rings) so I'm a little concerned they'll leak when I put gas to the carbs. We'll see what happens. Hopefully the rubber will swell a bit in fresh gas and they'll re-seal.

I took a heat gun to the gas tank paint and it peels off nicely with a razor blade, right down to the bare metal. Got most of the paint off the top of the tank. There was a lot of surface rust under the paint, especially around the gas tank cover. Once I got all the paint flecks off, I brushed it all with rust converter.

In between projects over the last few weeks, I cobbled together a colortune plug. Hopefully I'll be able to put it to use once the weather warms up.

+3c in Regina today... Feels like spring already... :pray:
 
Pic

Pic

Here she is ready for her first test start. Just waiting for my buddy to come by with his battery and we'll give it a crank.

After hooking up the carbs yesterday and and putting gas through the lines, carb #3's overflow started puking gas. So the carbs came off again. Should have tested that first before putting them back on... Lesson learned. Turns out #3's float was set a little lower than spec. Readjusted that and all four floats seal nicely. Carbs back on the bike.

At some point #4's spark plug cap came apart (there's a big gouge in the boot) so the internals spilled out over my nicely swept floor. Not sure how to put them back together, I disassembled the others and kinda cobbled #4's boot back together.
 
It's alive.... IT'S ALIVE!!!

It's alive.... IT'S ALIVE!!!

Test start went unexpectedly well. After about 30 seconds of cranking with the occasional fire, the bike puked 30 years of crap out the tailpipes and gradually stumbled to an idle. She'd only run on choke, would immediately die on throttle, and guzzled gasoline like a Hummer. My higher brain functions tell me there's fuel/air mixtures to adjust, but for now I'll do a victory dance and grill some steaks for supper.
 
Good news these old bike are awesome , I got two I need to get running soon to , it's fun and addictive,Brian
 
Back on track

Back on track

Well after a bit of a fuel supply issue the 750L seems to be running good. She fires on the first stroke (no choke) and seems to idle well. I gave it some hard throttle last night and blew a few more cobwebs out the pipe. My temporary gas tank is too small to warm the bike up and properly tune it, so I'm making the tank restore my next priority.

Last night I stripped the old paint down to the bare metal and gave the tank a good sanding. Put two coats of primer on the tank before bed. Gotta make up my mind what color to go with 'cause it's about time already...

- "Crake"
 
Some updates

Some updates

Well I've gotten behind on my updates. Here's a few new details....

Turns out she wasn't running as well as I thought - #2 & #3 run fine but no fire on #1 and #4 at all. Good spark, compression and fuel's getting through. Pulled the plugs on 2 & 3 and did some monkeying around with the fuel/air mix on the problem children. Now #1 and #4 fire on about 3/4 choke. So there's some progress. I wanna check the fuel levels in the bowls but I gotta get my hands on the appropriate tool. Gonna put all F&A matters on hold as I'm sick of stinking up my attached garage & house. My wife has been frowning and sniffing a lot. I'd do it outside but it's friggin' COLD.

Put about six coats of flat black on the tank and side panels. The decals were a little chewed up over the years so I gave them a few nice aluminum coats and they look ok. (This project is all about the cheap!) I skipped the clear coat (as it's seldom worked well for me in the past) and laid down a bunch of coats of automotive wax on top. I think it looks ok. Good enough for my purposes.

Took apart the seat. The leather is completely rotted and the seams are all coming apart. At least I'll have a material pattern to work with. The foam was in good shape. The pan? Very rusty. Dropped it in the electrolysis tub and gave her a jolt for a few days. (My tub isn't big enough for the entire pan so I have to keep rotating it). Pulled her out this morning. There's a few rusted through spots I'll have to fill with the welder but I think she'll do.
 
Looking pretty good!

Mine came with the same handlebars, I sent them off to the scrapyard with all haste.
 
More updates

More updates

Its been awhile since my last update, took a bit of a hiatus. I've been chipping away at a few things in the past couple months.

Got the tank hooked up, the petcock works fantastic, no issues there. I really hate the fuel line routing to the carb, I think I got some permanent scarring on the backs of my hands from trying to connect the fuel line after the tank was installed.

I pulled out the old sewing machine and about 20$ of marine upholstery and sewed up a half-assed seat cover. It doesn't look professional but it will do for now. Bought a new battery. Last week I ordered a $50 piston cup set for the master cylinder and got the front brakes working. The whole process went surprisingly smooth.

The bike was leaking a lot of gas last time I ran it. I suspect the #1 carb float is sticking. There's a lot of smoke out the left exhaust and #2, #4 plugs are pretty black. The damn F/A mix is clearly off and it's super frustrating to adjust those fuel screws once the carbs are on the bike. I suspect I'm gonna have to pull them off again and lean up all four cylinders. Right now the bike fires instantly with no choke at all so I'm thinking the mixture's rich on all four carbs. For now, I've drained the bowls and let her sit until I can roll it out on the pad instead of stinking up the garage.

Now, if the damn snow would melt, I might be able to take it for a quick trip around the block.

Here she is, sitting impatiently on the driveway. C'mon, spring!
 
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