1978 GS550 Idles for 5 seconds then dies

[joeman001]

Hi Ya'll,

I have a 78 550 and this thing was running fine the last time i started it up around 3 weeks ago and ive tried starting it over the past week and the longest ive gotten it to run was for 30 seconds before it sputtered out and died. Ive tried finding solutions on other forums with people saying it might be a CDI but ive read that alot of bikes before the 80s dont even have that and i cant seem to find one on the bike. Im thinking its a pilot jet problem as last time i filled up around a month and a half ago i did not put fuel stabilizer in it. I siphoned all the bad fuel off and put new stuff in and it didn't work, ive tried new plugs which didn't work, ive charged the battery to full which did not work and ive tried draining from the bottom of the carbs which produced gasoline that had fluid in it that was separated out from the gas and was oily. Honestly im just a college student with a cheapo bike and i dont have the tools or the know how to keep digging into this sort of thing. Does anyone have any ideas on things I could try to get it running? I do not want to dump the bike but i have never touched a set of carbs before and I do not have the tools or garage to do it but could get some if need be. Let me know what ya'll think, thanks for the help in advance.

-joe

[Big T]

Joe, you need to determine whether you have a fuel or ignition problem
So far, you're on the right track with fuel. Finding the contaminated fuel is a good start.
Now, about the idiots that told you to look for a CDI
No GS ever had CDI
Your bike came from the factory with points and condensor.
Take off the timing cover on the right side of the motor and see what you've got in there.
Start the bike and see if there's sparking.
Also, disconnect the fuel line at the petcock and test the fuel flow.. It should flow freely on Prime. On will flow when you apply vacuum to the vacuum port on the petcock
Also, when it runs, then stops, open the float bowl drains and see if there's fuel in there

I'm assuming it ran well recently?

[joeman001]

Hi Big T,

Talked to my dad on this earlier, he hasnt owned a GS before but a KZ440 and VFR750. He told me to do what you said and look to see if the points were sparking when i take the right side engine cover off that has the dual overhead cam badge on it. Again im a youngster and have only dealt with modern fuel injection so i am not sure what i am looking for. I did not see any spark coming off the (Distributor?) i just saw the main center piece spinning and lightly touching the two black pieces that are attached to the flat springs. I dont think its an ignition issue because i have pressed all the spark plugs against the frame and started the ignition and they all spark. Again i have no idea what the hell im doing so please tell me if i am missing something? Are the points farther back behind all the other parts of the (Distributor?)? Also any advice on how to not pour fuel all over the ground when disconnecting the fuel line? My petcock has (on, reserve and prime). Also no not really running that great recently. I live in columbus so starting last time was rough because its so cold actually had a fouled plug on the left cylinder (cylinder1). Ran a compression test every cylinder is around 120-130 besides far right cylinder which barely hits 100. I am sure that this is going to pain you as you all love GS bikes but i just need this thing to last another year to puts around campus. Before the winter it ran like a top, started it a few times during the winter now having problems. Thanks again.

-Joe

[Big T]

Joe, how long have you owned the bi ke?
Have you ever adjusted the valve clearances?
If the petcock is set to On or Reserve no gas should come out with the fuel line removed.
Get a foot or two of fuel line -5/8 and vacuum line 1/8.
Disconnect existing lines from the petcock and attach the new ones. Direct the fuel line into a glass jar, or similar.
Turn to Prime and observe flow for a few seconds.
Then, try On by sucking on the vacuum line. Repeat with reserve

Your description of the points sounds right

So, try these two tests
1. Run the bike, when it stops, open a carb drain and see how much fuel comes out. A small flat container is helpful
2. Run the bike, when it stops, pull a spark plugs and see if it sparks

[tom203]

Since you say it was running Ok two months ago...winter?? It sounds like your carbs got some water in them......maybe bad gas from station or someone messing with you.
I’d drain all four fuel bowls again. Don’t worry about any compression issues yet.

[Rich82GS750TZ]

Joe, I’m gonna take a different track here, just an opinion because you asked. And I write this in kindness and concern.

I have a kid at college in central PA, weather similar to Ohio. If my kid suggested to me that he’d like to keep a 42 year old bike at school on which to putt around campus, a bike he was not able to maintain or work on, wouldn’t know how to if he needed to fix anything, leave it out in the weather and expect it just to run when he needed it to, I’d tell him he was nuts.

I think you’re expecting too much. if you need transportation while at school, get a cheap used car.

Leave the bike back home in your dad’s garage if that’s a possibility. Make it something that you and he can work on together on your breaks from school.

Pay attention to Big T. He won’t steer you wrong. But there won’t be a quick easy fix on this bike. There’s likely years of neglected maintenance that you need to catch up on, and always more to do, but only if you’re willing to learn how, and you have the time and space to work on it. Quite often, you have to take something apart and leave it apart until parts are procured. That’s hard to do in a parking lot at college.

[joeman001]

Hey Rich,

No i am fine on transport i have a new Camaro which is what i spend most of my money on anyways lol. I have the GS550 because i love running around campus on a bike during the summer to friends houses and to the grocery and stuff. I understand what youre saying about it being an old bike and that its not going to run right when sitting outside all the time. The bike is already somewhat shot. Needs new drum brakes, new shocks, new seat, paint work, i need to replace the turn signal circuit its just a ton of stuff thar i dont want to fix and i just need the thing to run for the next year otherwise im gonna have to dump it for something with fuel injection. Gonna try what Big T said to do but its pouring down rain today. The previous owner was an older gentleman who had like 4 or 5 different bikes apart and seemed to know what he was doing and he said he did carb work and valve work on it but he just didnt restore it. It was a good runner before the winter but i only bought it because it ran good and he seemed like a decent guy plus it was 1000 bucks for a bike so i didnt really care too much. Only trying to get some help on the bike because i am trying to diagnose what the issue is before i decide to spend hundreds of dollars on a bike that has low compression on one of the cylinders. Thanks for all your help will keep you guys posted after i run a few tests suggested by Big T.

-joe

[Maddevill]

If you noticed a separation line in the gas, you have water in your fuel. The water will sit on the bottom. Drain all the gas in the system and start with fresh. Also check your gas cap for leaks or park it under cover.

Mad

[joeman001]

Hi again Big T,

So i disconnected the fuel line going to the carburetor and then watched the flow on res, on and prime. Prime obviously dumped a lot of fuel but on reserve and on the petcock was constantly dripping fuel. I drained the line going to the carbs and i drained float bowls 1 and 4 and the gasoline looks horrendous. I actually was going to drain 3 and 2 but float bowl drain screw 3 is stripped so i cant really do much on that. I am going to say with 99.9 percent certainty that the carbs are totally clogged because the fuel looks so bad and there is so much separation. See pictures attached. What do you think i should do going forward? I reattached the line and primed it and then set it to on and i got the bike to rough idle around 1000 rpm for around a minute and half so i think we are getting somewhere. To answer your question on ownership i bought it in aug of 2020 and the guy before me said he did valve and carb work on it before. Thanks for all the help again youre a great resource.
unnamed.jpg

-Joe

[timebombprod]

I'd do a carb rebuild and replace the petcock with an OEM one, somebody has the rebuild for these carbs in there signature. Super easy (but possibly tedious), if you can take the carbs apart on the fuel rack you can take them off the rack no issue, just number the carbs, and also the pieces for the float assembly should be numbered to keep the fuel levels the same on each carb. Just don't get any rubber in the carb cleaner, could use pinesol if you want to get the rubber cleaned up too.

Checkout the valve clearance, if your bike has a constant tick that sounds kinda like a coin then you might have a valve tick. The gaskets are around 50 dollars and so are the right petcocks, I'd check amazon for the petcock and ebay for the valve cover gasket to see if you can get a better price, but use a website like suzukipartshouse.com first to get the initial prices of things.

A faulty petcock will make your bike sound like everything's going wrong internally. You'll hear constant pops and sputters and the bike will not want to move up the rpms really at all, I rode my bike for maybe 2 neighborhood roads with a faulty petcock and it was like riding one of those robotic bulls.

[cowboyup3371]

Use the existing jets, get new o-rings from www.cycleorings.com (the owner is a member here), and new bowl gaskets from partsoutlaw.com or z1enterprises.com.

Pick up a gallon can of Berryman’s carb cleaner as it has the small basket to hold parts in it. Then, Follow the procedures for the VM carbs on Basscliff’s site (http://members.dslextreme.com/users/...rb_rebuild.pdf)

Also, there are several members within 70 miles of you. The forum whisperer, Steve, lives in Centerville while I live in Miamisburg (both in the Dayton area) and Storm64 is up towards Cleveland. You can always give me a shout if you want some help.

One last thing, I’ll be at Iron Pony on Sunday to get new tires for my 550 and may even have time to go see my daughter in Newark if you are interested in someone stopping by.

[steve murdoch]

Another example of the quality members on this site.
You're a good man, Scott.

[Maddevill]

If you don't address the water in your fuel, you're wasting time. Just my .02

Mad

[Big T]

You need to completely drain your fuel system.
You still have water/ whatever in there

Drain the gas tank, then remove it and leave it open to dry.
Drain the carbs
Check the oil for gas contamination

[joeman001]

Fixed!!

I got a 5/16 line and drained all the gas from the system including the carbs. Was still running only two cylinders until i pulled the spark plugs and saw that cylinder 3 was fouled pretty bad. After replacing it started to idle on 3 cylinders and when it got to temperature cylinder 4 actually started firing even though it wasnt when it was cold. I believe the compression at cold temps is too low on that cylinder but on higher temps its enough to ignite the fuel. Took it to the gas station and for a half an hour ride and it runs pretty damn well for a 42 year old bike that definitely has seen better days. Thanks for all your guys help on this problem. Youll probably see a post in the electric section about a bad turn signal circuit here soon.

- Joe