1980 gs550L 1st bike build

[JEEPRUSTY]

You are not supposed to leave the petcock on PRIME
I do not know about your but there are three setting on mine
PRIME ON and Reserve

The first one is open and fuel flows via gravity.
The latter settings require vacuum fromt he engine to allow fuel to flow.

Check your oil for gas and change it if there is any evidence of contamination.

Its all in the Mega-Welcome...............

 

[CCC-TT]

What I meant was that when I bought the bike and for the first 3 days that Ive owned it (before I knew to look at the petcock) it had been set to "PRM". After realizing that was the incorrect setting I changed it to what apparently is the run setting(the notch in a vertical position in line with an arrow pointing down that says "FUEL" above it). After setting it to the run position and going to sleep, the fuel had all drained out over night.
This, I realize, is a petcock issue. but my other concern is that when it had been set to PRM, there was a slow leak out of the bottom of carb #2. Would this be consitent with a petcock issue or am I now also facing the issue of stuck float needle?
And again, thanks for the responses guys. This forum is appearing to be much more directly informative than the lexus/supra forums that I am used to with my car.

 

[mike_of_bbg]

That's a bad petcock. The vacuum hose from your petcock goes to carb #2. It's supposed to work that the vacuum from the carb pulls on the back side of the diaphragm and allows fuel to flow across the front side. If that diaphragm develops hole(s), it can allow fuel to run down straight to your #2 carb and promptly find it's way toward the ground with gravity's help. Success stories with rebuilds are fewer than failure stories, and it's generally recommended to shell out the $60 or so for a new petcock.

Though, as an 80 yours might have an "alien" petcock. Does your petcock have a lever and 3 settings? Some 80 models used a rather odd petcock which was quickly abandoned by Suzuki. Of course they used different bolt spacing, too.

Some of that fuel may have run IN to cylinder #2 then down to the crank case. Make sure the oil is not overfull and smelling powerfully of gas. Also make sure cylinder #2 isn't full of gas before you try to start it again and hydro-lock the motor.

 

[CCC-TT]

Thanks Mike,

Now you can see what I'm working with.

It is set back to PRM for now to avoid the gas flow issue. My next questions:

- why will the bike run fine with it set to PRM but as soon as I move it vertical the bike will not idle at all? It will start and run but as soon as I let go of the throttle it dies.
- How will I check to make sure the cylinder is not full of gas? And if it is, what will I need to do to remedy the situation?

 

[Mad Mark]

as long as your having fun with it. its your bike do what ever you want.

i would have recomended getting it running before doing cosmetic stuff though

 

[mike_of_bbg]

This thread describes the "dreaded 1980 petcock":

http://www.thegsresources.com/_forum/showthread.php?t=176459&highlight=1980+petcock

There's no reserve setting on that one. As to why it would idle on PRI but not ON, it's probably because the ON setting is flooding cylinder #2 down the vacuum line. Check the vacuum line and see if there are signs of fuel in it.

OEM replacements for that petcock are still available for about $74 + S/H:

http://www.boulevardsuzuki.com/fich...y=Motorcycles&make=SUZUKI&year=1980&fveh=2111

Or OEM-ish for a bit less:

http://www.z1enterprises.com/Petcock-vacuum-Suzuki-50mm-bolt-spacing-2636.aspx

The spacing is unfortunately different from other petcock models, so it's not easy to retro-fit the ones from other years. I've seen pictures where the bolt holes have been elongated on other years' petcocks, but there's potential for gas leakage with that. You might be able to find a suitable adapter plate and use a Pingel or similar tap, capping the vacuum port on #2, losing the vacuum function, and just having to remember to turn it off.

If you leave the petcock on PRI or get a non-vacuum type like a Pingel you run the risk of the carb needle valves not holding back the fuel and having leaking issues again. There's no real "ideal" solution.

Just pull the plug from #2, peer in with a flashlight, and make sure you can see the top of the piston to verify it's not full of fuel.

If your oil level is high and it's gassy because some of it leaked down that way, you'll want to change the oil.

 

[CCC-TT]

Yea none of that seems to be good news.

Judging from that link, the PRM function is what I thought was the ON position. So last night when it flooded out everything, is when it was set on PRM. Since ive had it then, it has been set to the middle between PRM and ON. I'm going to switch it over to the ON position and see what happens.
I had considered getting a fuel cut off valve and installing that in-line on the fuel line in order to stop fuel flow when the bike is off. Would this work as a temporary fix?

 

[cowboyup3371]

Like Mike said that is the dreaded 80s petcock and will prove to be a headache for you. Please go back through the top 10 newbie mistakes as well as Basscliff's information and get all the proper maintenance done before you go too much further. You'll want to buy a replacement petcock and I think in some of the threads about that style discussions were made about possibly putting a Pingel on there. You'll have to manually shut off fuel when you turn off the bike but it might help out some.

 

[CCC-TT]

I just went out and started messing with it. I set it to the actual ON position and it started and ran the bike with no issues. The bike runs and idles, a little low, but it idles. I also pulled off the vacuum line and did the thing where you suck on it to see if fuel comes out and none did on either PRM or ON. I did notice that when the bike was off there is still fuel visible in the fuel filter so i dont know how much that plays into anything.
I also checked the oil and I didnt particualrly notice any gasoline smell from it. Though there didnt seem to be much oil in there, at least I didnt see any when I looked in with a light, only a coating of oil on all the parts inside.
I left the petcock set to the ON position now to see what happens and try and get a better idea of the problem. In the mean time I will go check his site again and see what I can come up with.

 

[CCC-TT]

Update:

After moving home and messing with the bike some more she is running perfectly. I charged the battery up for a day and she's back to firing up immediately when the button is hit. I ran another bottle of fuel system cleaner through it and now she runs better than ever. I do think that I may have to turn the idle adjustment screw maybe a 1/4 turn to raise idle slightly (its sitting right at 1k but sometimes wants to fall below)...
-Can anyone reccomend an ideal idle setting?

A few days before moving home I bought a set of drag bars but after a test fit I was less than impressed so its back to the stock bars, though I did lean them farther forward on the mount in order to stretch my arms out a little more

At this point I dont have anything to do to the bike other than idle so I'll ask for your opinions here. Now I have already decided to go back to real suspension in the rear, just something lower than stock... but what else would be some cheap yet effective mods I could start working on to improve the performance of the bike?
I like the fatter tire in the front look that Ive seen on some bikes... any pros/cons to this and how is it to fit a wider wheel/tire on the stock forks?

-Brakes? (with my sc300 I was able to swap the brakes from an LS400 and a Supra TT... anything like this in the bike world as opposed to going completely aftermarket?)

-Pod Filters? Ive read things about the issues with re-jetting after these mods but I own a wideband and have experience tuning fuel injected motors so would this still be more trouble than its worth?

-Exhaust? Again, Ive read the issues involved with re-jetting after exhaust but I'd like a little more throaty sound from her. Any suggestions to a decent sounding exhaust that doesnt throw off performance too much?

Really any suggestions as to things to do to the bike other than putting it back to stock... I need something to keep my hands busy.