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Old 03-21-2015, 03:28 PM   #1
G54B OP
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Joined: Oct 2013
Location: Gunningbland, NSW, Australia
Oddometer: 50
'78 gs550

I have this:




My uncle bought it new in '79, rode it for fifteen years, then Dad had it for a few years, then it was parked in an old pigshed on the farm.
61,000km, motor was rebuilt less than 5,000km ago, did have points but was converted to electronic ignition sometime in the 90's, and it's all there and in pretty good shape for a bike that's been sitting for as long as this one has.
The kicker: It sat for a while then wouldn't go again. That was 15 years ago. Dad reckons it's the electronic ignition module, or I've been told that it could be a pulse coil issue.
Plan is to make it go, make it stop, replace everything that needs replacing and ride it.

First order of business: How does one remove the carbs without breaking anything when the airbox boots and intake manifolds have gone rock hard?
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Old 03-21-2015, 03:48 PM   #2
Johann
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Oddometer: 571
General bodges that I have used on four cylinder UJMs......

To get the carbs off look under the seat to see where the airbox is mounted at the back. If you are lucky it will be bolted to either the rear subframe or part of the rear mudguard assembly. You might be able to move the airbox back an inch or two which will make removal a lot easier.

To replace leave individual rubbers in a pan of boiling water . When you remove them from the pan they will be soft and pliable for about 30 seconds before they cool and harden again. Either you manage to fit them before they harden or put them back in the pan for a second go.
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Old 03-21-2015, 04:07 PM   #3
zap2504
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Quote:
Originally Posted by Johann View Post
To replace leave individual rubbers in a pan of boiling water . When you remove them from the pan they will be soft and pliable for about 30 seconds before they cool and harden again. Either you manage to fit them before they harden or put them back in the pan for a second go.
Something I've saved from past posts (don't remember where) concerning re-vitalizing rubber carb mounts:
"My carb boots on a Honda CB 550 were just completely hard after sitting for 23 years. Just horribly expensive to replace with OEM. With nothing to lose, I immersed them in lacquer thinner and checked them twice a day. The things swell up and you would swear that they are ruined, but they shrink back to normal in a few days. Some guys also use wintergreen available at drug stores and make some sort of brew mixing it with the solvent. I just use the lacquer thinner until the boots soften enough and then soak the boots in the wintergreen for a day. As they start to shrink, the wintergreen sucks in to the rubber. The wintergreen at a cheaper price is also known as Thor Tire Prep #12 and available at kart shops to soften racing tires.

Thoroil.com to find the stuff...15 bucks for a one quart lifetime supply.

My carb boots shrank back to normal in a few days, but I make no guarantees on yours. The boots are completely supple and I can squeeze then together with 2 fingers..."
And:
"I recently ran into a formula for softening age-hardened rubber... couple ounces of wintergreen oil in a pint or so of xylene. I just did some intake boots & they went from rock hard to like new flex in 24 hours. I am astounded at how well it worked. The wintergreen is supposed to have a natural plastisizer in it called meythyl salicylate. The test bits did not swell up noticeably and are still pliable after a couple days sitting on the bench. I put another set in mix yesterday & they show improvement, but not as dramatic as the first set. I intend to leave them in until tomorrow & see if they continue to improve. It's the same mix though, so maybe some fresh materials would speed things up.

I got the oil from a local health food store, another source is homeopathic medicine. I hear that sports medicine uses it too.

so.... it's about 3 weeks since I made the original post. I also treated a 2nd pair of intake boots, and today I installed them. The first set I did had some small cracks (before the treatment) so I used the better set. Anyway, all the boots are still soft as when they came out of the mix."
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Old 03-21-2015, 04:09 PM   #4
lkr57
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I had a 77 GS550 just like yours. You can unbolt the airbox and slide it back 1 or 2 cm, but that's about all. I don't think it can be removed until the carbs are out unfortunately.

I'd try a heat gun on the boots to warm them up and get them more pliable and also spray them with some silicone lube or WD40. Then you just have to kind of wiggle the carb rack out. It's a tough job but you will get them out even though it may seem impossible at first!
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Old 03-22-2015, 07:00 AM   #5
Pussboy
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Joined: Aug 2002
Location: Chesterville, OH
Oddometer: 388
My very first bike was a 1978 GS550! Dark blue with the orange pinstripe. I loved that bike and it started my infatuation with motorcycles. I am on bike 15 now and I still remember how great that bike sounded with its 4 into 1 header!

Great bike! Good luck with your project!
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Old 03-22-2015, 08:55 AM   #6
shakeybone
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I have a GS650E myself, love the GS bikes. Check out thegsresources.com for lots of help and info. Also http://members.dslextreme.com/users/bikecliff/
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Old 03-22-2015, 09:47 AM   #7
nate25tenn
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I have an '80 GS550. Have to slide back the airbox then tug the carbs out before the box comes out. That link is a total life saver for these bikes. Also check out GSResources.com.
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Old 03-23-2015, 12:11 AM   #8
G54B OP
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Location: Gunningbland, NSW, Australia
Oddometer: 50
Cheers fellas. Dad said that getting the carbs out would be a mission, so here's hoping it goes relatively smoothly.
Those should just need a bath, easily enough done. What I'm worried about is the suspected ignition issue, I have no idea where Dad got the electronic ignition from, and whether or not it's even possible to get a new module for whatever he used, if that's even the problem. Guessing pulse coils would be easier, as they're not likely to be universal-type aftermarket jobbies.
I guess I'll find out when I pull the mag cover.

This is second on the list of bikes I have to get done at the moment, it's going to stay where it is until I get to a point where I feel I can take a break from fixing up my first bike (an 11/1980 DT175), then it'll be full steam ahead.

I've owned a number of old dirtbikes but this will be my first roadbike, should be an interesting experience... Compared to my current bike (10/'81 IT250J) it's a big, heavy, complicated beast, haha
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Old 03-25-2015, 08:29 AM   #9
IHWillys
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Quote:
Originally Posted by zap2504 View Post
... another source is homeopathic medicine...
zap2504, good tips on reviving old carb boots.

However on sourcing wintergreen... Homeopathic "medicine" would not have any wintergreen in it. It would be water or alcohol or anything but what the homeopathic "ingredient" is. Check out the "law of infinitesimals" purported by the founder of homeopathy and thus the intent to dilute past Avogadro's number.

Homeopathy is the king of placebos. I don't think the carb boots would be as easily fooled as we humans are.

Ken
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