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Hard to start/keep running 77 550

  • Thread starter Thread starter bobth1019
  • Start date Start date
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bobth1019

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I'm having a starting/running issue with my 77 gs550. I picked up this bike a short while ago. Pretty good shape but hadn't been started in years.

I pulled the carbs, cleaned them (at this time multiple times) and the best I could do is similar to the issues in another post "Engine Not Getting Fuel After VM Rebuild" which reading through was helpful. I had fuel filling bowls but no starting for other than a moment or two with starting fld being sprayed directly into carbs. Fuel would come out overflow tubes.

As I said at this time I recleaned carbs out more than once to be on safe side, reset the float heights and now I can get the bike to start but only with air cleaner box off and carb inlets plugged with cloth (I gave this a shot just for the hell of it as a last resort and was surprised to hear it start). Then it runs alright till I pull cloth out and dies. And at this point (after resetting float heights) no more overflow issues.

So yes, a touch too lean but what is creating such an extreme issue with this? I can't see anything that is so wrong as to create this. What should I look at now?

thanks, Bob
 
Did you dip the carbs and rebuild them with new orings as per the carb cleaning tutorial ?

Sounds like your petcock is toast and difficulty starting is a sure sign of the valves needing adjustment. :)
 
Thanks for taking a look, Larry...

The petcock seems to be working ok as fuel flows pretty well from it and once the bike started the valves sound ok so not sure if those are the issues. I keep feeling it's something obvious I'm missing. All the carbs are doing the same thing for one thing.
 
Is the air filter solidly clogged causeing it to be choked to death? Have you tried it on prime and leaving it on prime once it starts? If it stays running on prime, does it die after a few minutes in the on position? Is the vaccuum line from the carbs to the petcock NEW and not any hairline cracks making it suck air? Have you replaced the intake boot Orings? Are the boots themselves free of cracks in the rubber where they meet the steel flanges? Does it have an inline fuel filter, and if so why havent you eliminated it yet? Have you pulled the petcock to see if the internal periscoping filter is clogged? Are the metal band clamps that secure the carbs in the boots stretched and causing an insufficient seal to the carbs...possible air leak there?
 
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Hi,

These bikes don't run too well if the airbox is not installed. It creates an air/fuel mix that is way too lean.

Clean the carbs properly, according to the guides on my little website. Fix and seal the air intake system according to the guide on my little website. Go through the maintenance lists in your "mega-welcome" and take care of all those issues. Skipping steps or taking shortcuts will leave you frustrated. Let us know what you find.


Thank you for your indulgence,

BassCliff
 
The other guys problem was mainly fuel screws broken off in the carbs, blocking the gas flow

Sounds like that's what you have also, constricting the air flow causes fuel to flow from other places inside the carb
 
Thanks again for taking the time...

I've looked at/tried all the very good points you mentioned, Chuck, and all seems well or haven't seemed to help. Literally, the only way it will start/run for any length of time is to plug the carbs inlets with paper towel or t-shirt. The carbs seem ok at this point. I've pulled them apart and went through them now 3-4 times assuming I'm missing something so at this point I think they're ok. I tried a different gas tank and no difference. With the air box /filter on it's a no go because I can't plug up the carbs enough to get it started. Any combination of choke, gas, petcock other than plugging up the carbs doesn't make a dent in this. Way to much air but nothing is obvious to me....I have a feeling it's something right in front of me but I don't know what.
 
VMs...Did you use a bread tie wire and poke it ALL the way into the pickup tubes....the fixed thin brass one sticking down from the carb bodies? Did you remove and poke all the holes out in the emulsion tubes? And the pilot jets? Are all the choke plungers clean and clear passages? Are you certain the slides are falling all the way down? A miss routed cable will cause them to stay up a bit..and any little bit they are up from the bottom and its not gonna want to start. Be sure they are falling all the way down and that the bench sync has been done correctly. Dont twist the throttle open to try and get it to start..that does the same thing as the slides hanging high. Just choke..leave throttle alone and crank. I suggest you pull them recheck everything as far as the holes and passages being clear. Use carbs spray and blow compressed air both ways down all the orfices and passages. Turn the big idle knob all the way out till there is no pressure on the throttle linkage and recheck the bench sync. Make all slides just a sliver of light thru them and even looking. When you readjust the idle knob, just touch it off and add about 2 turns max. An over adjusted idle knob will also open the slides and it will not want to start. Try the idle knob before you remove them though.. reset it like i described.
 
Hi,

A '77 would be VM carbs.

bobth1019 said:
the only way it will start/run for any length of time is to plug the carbs inlets with paper towel or t-shirt... With the air box /filter on it's a no go because I can't plug up the carbs enough to get it started...
Click to expand...
Clean the carbs properly. CLICK HERE to see how. They need to be completely disassembled and dipped for up to 24 hours. Then reassemble them with a new O-ring kit from http://cycleorings.com.

Seal the airbox and repair the air intake system so that it doesn't leak. Whatever you do, don't do these: Top 10 Newbie Mistakes

The remaining critical items are as follows (from your "mega-welcome"):

***********Quoted from Mr. bwringer************
Every GS850 [and most other models] has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting. It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years. It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

1. Intake O-rings (install NEW OEM or Viton only - common nitrile O-rings will quickly deteriorate from heat)
2. Intake Boots (install NEW -- these cannot be repaired)
3. Valve clearances (more important than most people think)
4. Carb/airbox boots
5. Airbox sealing
6. Air filter sealing
7. Petcock (install a NEW one)
8. On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)
9. On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.
10. Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.

What I have noticed at the rallies is that very, very few 850Gs are actually running right. Make VERY sure it's actually running the way it's supposed to before busting out the modifications.

Brian's E-Z and fun plan for GS850 happiness:

1) Seal the airbox and air filter with weatherstripping.

2) Ensure no intake leaks. Spraying WD-40 or water doesn't tell you much, since very small air leaks can cause problems even though they won't suck in enough WD-40 to make a difference. Replace your intake boot o-rings and boots if needed, and seriously consider spending the lousy $28 for new airbox/carb boots.

3) Ensure clean carbs with correct settings, new o-rings, and original OEM jets. No, not just squirted with something. I mean completely disassembled.

4) Check/adjust valve clearances (Manual calls for every 4,000 miles. This is not optional.)

5) Ensure healthy electrical system.

6) Seriously consider upgrading coils and plug wires.

7) Install new, stock NGK B8-ES plugs gapped to .031".

8 ) Fine-tune float height and idle mixture screw to ensure best off-idle transition.

9) Clean air filter and reinstall with only the lightest oil mist -- over-oiling and/or letting the filter get dirty is a common and critical mistake, and will make the bike run funny at low speeds and run rich. This may take a few tries.

10) Make sure the exhaust seals are sealing.

11) Ooh, much better now, huh? You're gonna need upgraded suspension - Progressive or better fork springs and shocks. Set suspension sag appropriately.

12) Upgrade brakes with new pads and stainless lines to deal with all that extra speed.

13) Install new petcock, since I'm going to head to the roof with a rifle if I have to read about yet another #2 plug fouling and failed hillbilly attempts to rebuild the petcock and/or deny there's a problem.

14) Oh yeah -- check compression somewhere in there to ensure the valves and rings are reasonably healthy.

15) You'll probably need new OEM clutch springs -- the clutches last forever, but the springs get tired after 20 years or so under pressure. E-Z and cheap.
Carburetor maintenance:

Replace the intake boot o-rings, and possibly the intake boots. Here's the procedure:
http://bwringer.com/gs/intakeorings.html
Here's an overview of what happens with this particular problem:
http://cycleorings.com/intake.html


***********************************


This is the plain and simple truth. It's a 30 year old machine and needs a lot of love. You'll find a lot of "how-to's" on my little website.

Thank you for your indulgence,

BassCliff

 
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bobth1019 said:
Thanks for taking a look, Larry...

The petcock seems to be working ok as fuel flows pretty well from it and once the bike started the valves sound ok
Click to expand...

Perhaps you can tell us what OK valves sound like?
And valves which are too tight and getting ready to burn up, what exactly do they sound like??

Do the maintenance, or buy a new bike.
 
I would suspect something in the way you are setting the floats
 
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