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Bike Running Rough - HELP!!!!

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

Guest
Hey Guys, I'm still trying to get my 81 GS550L on the go after all summer and the biking season is pretty much over here in Newfoundland, Canada. I'll start by telling you what I've done:

New Points & Condensers, Static Timing, New Spark Plugs, Inline Fuel Filter, Petcock Rebuild Kit, New Float Needles and Seats for all 4 Carbs, New pilot jets for all four carbs, New rubber plugs for pilot jets for all 4 Carbs, Complete carb cleanup as per carb cleanup series.

Here's the problem - I still can't get one bit of sense out of the bike. It spits and sputters, dies out between 2000 to 4000 RPM, #4 exhaust pipe is cold (with lots of spark). It seems to me like the bike is only running on 3 cylinders. I'm getting frustrated with the bike and I don't know where to turn next. Right now it's barely mobile.

Please help with specific suggestions.

Thanks,
Craig
 
All your problems could very easily be attributed to the bike only running on three cylinders. You say #4 pipe is cold. Does 4 stay cold when you start the bike using choke? After it warms up enough to take it off choke and have it running on the idle jets, is 4 still cold. If you run the bike for two minutes at about 2000 rpm, does 4 still stay cold? Knowing what rpm range the pipe is cold in will tell you which part or parts of the carb are not working correctly. If 4 stays cold in all ranges and never warms up, then its probable it is still badly clogged and still in need of cleaning, or the float valve could be stuck closed, or there could be a BAD air leak on the induction boot between the carb and cylinder head. If you have CV type carbs, the diaphram could also be holed/cracked and inoperable if the carb doesnt work in any rpm range. If it works in some rpm ranges and not others, this would rule out a fuel availability problem. So the question is: is the carb working partially, or not at all. If partially, what ranges does it work in?

Earl
 
Thanks Earl,

Here's the best explaination I can get. I start the bike with full choke and it seems to run on all four. When I let the choke in, the bike runs really rough. As I begin to ride it the power is crap, but after a few moments, the power comes and goes. When the power comes, the bike works great above 5000RPM - good accelleration and smooth transition between gears. When the power goes, it definetly feels like the bike's running on three cylinders or less. "Sometimes" when I pull the choke, it seems that all four cylinders cut in and the power is normal, and the bike's rpm will shoot up to around 3000. I hope you can pick some sense to this explaination.

Oh Yeah, a note on the plug colors:

1&3 burning brownish gray
2 burning sooty black
4 not burning at all - same color as installed.

Thanks Again,
Craig
 
OK Craig, considering cyl's 1 & 4 fire together and 2 & 3 fire together, if it was an electrical problem, it would be very unlikely #1 would fire and #4 would not and #2 would run rich and #3 would run normal. You said you had good spark on all four plugs anyway. That would rule out wiring connections also. I think you have a fuel flow or fuel draw problem. Do you have the stock airbox installed? The bike will not run right without the airbox. Did you install new fuel and vacum lines? The first thing I would do is determine if you have unrestricted fuel flow from the petcock. I would fill the tank and then put a long length of clear vinyl or neoprene tubing on the petcock with the open end runing into a gas can. Turn the fuel petcock to prime and see if it flows uninterruped for maybe 10 minutes. If it does, I would switch the petcock to run and suck on the vacum line to see if the fuel valve opens in this position and fuel still flows into the gas can. Since you are using an inline fuel filter, make sure you leave it connected so as to check fuel flow through it. Some filters are highly restrictive. If you have good fuel flow on both petcock positions and are using the stock airbox, the next thing I would do is to reconnect the fuel lines. Put the bike on the centerstand, turn the petcock to prime for about 30 seconds and then turn it to run. (bike not running. I would get 4 paper cups and drain each float bowl into a cup. check to see that each float bowl is getting fuel to it and holding the same amount. Let me know what you find and we'll go from there.

Earl

CraigPardy said:
Thanks Earl,

Here's the best explaination I can get. I start the bike with full choke and it seems to run on all four. When I let the choke in, the bike runs really rough. As I begin to ride it the power is crap, but after a few moments, the power comes and goes. When the power comes, the bike works great above 5000RPM - good accelleration and smooth transition between gears. When the power goes, it definetly feels like the bike's running on three cylinders or less. "Sometimes" when I pull the choke, it seems that all four cylinders cut in and the power is normal, and the bike's rpm will shoot up to around 3000. I hope you can pick some sense to this explaination.

Oh Yeah, a note on the plug colors:

1&3 burning brownish gray
2 burning sooty black
4 not burning at all - same color as installed.

Thanks Again,
Craig
Click to expand...
 
O.K. Earl. I'll test for uniterrupted fuel flow this weekend and get back to you early next week. I think you're right about the electrical assumptions. We'll see what happens anyway.

Thanks Again,
Craig
 
carbs syncronized?

carbs syncronized?

I had a sililiar problem with my 1100. The carburetors were so out of sync, that one of them barely ran at all.. IF you haven't addressed this issue then take a look at it. I read the book and found the adjusting screw s and without the mercury sticks I syncronized them enought to make it rideable.. later I got ahold of some mercury sticvks and did it right.. Just a thought.... good luck with it.. joe
 
Hey Guys, just getting back at my GS550L troubleshooting. I took off the rubber intake manifolds today and three out of the four had separation of the rubber and steel. Could this have accounted for all my problems that I experienced as explained above? Anyway, I will be getting all new intake manifolds and strip the carbs once more. Also, do anyone know of a brand name of a 1 gallon can of carb soak that can be purchased in Canada?

Thanks Again
Craig
 
It is common for there to be some seperation with age. That doesn't necessarily mean they are leaking though. Just pull them off and examine them closely from the inside to see if the cracks go all the way through. Some guys will use WD-40, carb cleaner, or starting fluid sprayed around the manifolds with the bike running to see if the idle changes while spraying.
 
I checked the intake grommets again and 3 of the 4 we separated from the metal all the way through. A couple of new items, on the airbox side of the carbs, only 1&4 have clamps while 2&3 do not - is this right or should all four have clamps. Also, what type of o-ring goes between the metal on the grommet and the engine?

Thanks,
Craig
 
clamps

clamps

not sure about the oring grommet question, but yes all 4 carbs should have a clamp on both sides of the carbs holding them to the engine and to the air box. You can replace these with just a clamp from an auto parts store (suzuki will probably want an arm and a leg for the things)
 
Yes there should be an O-ring between each intake boot and the head.
Dink
 
I bought 4 new OEM exhaust "O" rings at my local dealer a couple months ago. A set of 4 was less than $5. I dont know the composition of the rubber.

Earl


CraigPardy said:
what type of o-ring goes between the metal on the grommet and the engine?
Click to expand...
 
Thanks - got the OEM part number for the o-rings from bikebandit.com. Will be a couple of weeks before I post to this string again - Craig.
 
Be sure you use a hammer type hand impact driver to remove the intake flange screws. A normal screwdriver will ride up and strip the heads as will an air impact driver. When you are ready to remove the screws, take the phillips bit you will be using out of the impact driver and hold it in the screw, striking it with a hammer to seat it exactly to the screw. Then put the bit into the driver being sure to hold the driver VERY tightly against the screw head.
The blasted screw heads are soft and they strip easily. If you do strip a head out completely, you can get another chance if you take a dremel tool and with a cut off disk, cut a slot so you can use a slotted driver bit.

Once you have them removed, I think its best to replace them with hardened metric Allen screws.

Earl


CraigPardy said:
Thanks - got the OEM part number for the o-rings from bikebandit.com. Will be a couple of weeks before I post to this string again - Craig.
Click to expand...
 
About the only time I've had a cylinder stay completly cold and not burn the plug, the float was in upside down, this shoves the needle into the seat and holds it shut.
 
trotski said:
About the only time I've had a cylinder stay completly cold and not burn the plug, the float was in upside down, this shoves the needle into the seat and holds it shut.
Click to expand...
Isn't that stock for Australia, being down under and all? :lol: :lol:
 
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