1980 GS550L Won't Accelerate

[chef1366]

I did not use the retainer.

[KEITH KRAUSE]

#2 shouldn't have a wet plug. That needs to be fixed first.
Petcock may be leaking through vacuum line to #2? Float level wrong or sticking float? Compression has been checked? Solid electrical connections? Sorry if I'm mentioning things you've checked. Something's causing a high fuel level or poor spark/combustion in #2.
Seems like the carb rebuild may be where your problems started?
The Mikuni brass jets should never be replaced unless there was certain corrosion or other damage. Jet kits sometimes have incorrectly sized jets too. If it was my bike, I'd put them all back, including the float valves and original seats. The valves and their seats wear as a unit and shouldn't be mixed up but I would still put them all back and re-adjust the float levels. You ARE setting the levels at the correct part of the float? If the carbs weren't leaking out the overflow lines, there's usually no reason to change the float valves.
Are you positive the rubber diaphragms are installed/seated correctly? Just takes one failing to cause your problem.
The new exhaust will cause some decel' pop. Usually, an additional 1/2 to 1 full turn out (from factory setting) on the mixture screws will help. Some pipes require a stage 1 jet kit if it really bothers you. Still may pop a bit though. 3 1/2 turns out on your mixture screws seems a bit too much for just a pipe. And it still pops? Problem is somewhere else in the carbs I think.
A good vacuum synch may stop the popping too. Hard to blame the popping on anything else until the vacuum synch is done. Basic maintenance.
Focus on that wet plug and all the possible causes.

[KEITH KRAUSE]

By the way, your petcock should have the slot turned horizontally. That's ON.
Vertical is PRIME.

[flyingace]

After a high-speed plug chop, the plug really shouldn't be wet. If one cylinder is not firing, it could explain your symptoms - the bike runs, but you're dragging a useless piston around.

The quickest/easiest thing to do is swap the #2 and #3 plug wires and see if the wet condition switches to #3. I assume you have fairly new plugs and have already eliminated them as the problem. If it does, it's a coil/wire/cap problem. If that makes no difference, and you have good compression, it's probably something in the carb.

[ddaum]

Finding My Inner Doofus....

I FOUND THE PROBLEM!!...somehow...
\\/ \\/ \\/

Wow, the bike runs GREAT now, and guess what... it's 75 degrees out too!
Here's what I did:
I removed the carbs, pulled each slide and checked the diaphragms with no discrepancies. Then I pulled each needle out and found that all were assembled correctly except for #1. Somehow I put the washer below the spring on the needle when it's supposed to be above it, so I fixed that and installed all the slides. Next, I pulled each float bowl and re-measured the float heights. I had them all set to the high end of the spec range(low fuel level). I must have mixed that up, so I set them all equal to the low height setting (higher fuel level). Then, I re-installed all the stock jets, air, needle, pilot, and mains. I was also confused in my posts above because I did leave the stock needle valves and seats in, so they were good. I then re-assembled and installed the carbs with a new fuel line minus the in-line filter. I also re-set the air screws from 3.5 turns out, to 2.5 turns out. Then, WHAM-O! She started up and idled great, and now she pulls like a dream at all throttle settings! The popping is still there, but not nearly as much, only once in a while, but I think that as Keith said, a good vacuum sync should remedy that. Other than that, all I have left is to tune the air screws for high rpm at each cylinder, then vacuum sync. But she already runs very good with my bench sync. I rode around for a bit and chopped the engine at about 60mph again and checked the plugs. #2 wasn't wet this time and all were a little darker in color, but the color was even on all four. So I was definitely running lean before. I still may be a little lean but things are better now. THE POWER IS BACK!
Thank you all for your suggestions, comments, and ideas!

BTW- I'm 6'3" and about 280lbs, a BIG guy for this 550, but it pulls me around good. With my size, is it expected not to get more speed than what the speedo says (85mph)? Today I had a bit of a headwind and got 75mph and climbing slowly before I had to slow for traffic. Is this expected for my size and weight? Bike has no windshield or fairing and is an "L" model, so there are almost no aerodynamics.

Enjoy the weather!
Dean

[jimg]

I FOUND THE PROBLEM!!...somehow...
\\/ \\/ \\/

BTW- I'm 6'3" and about 280lbs, a BIG guy for this 550, but it pulls me around good. With my size, is it expected not to get more speed than what the speedo says (85mph)? Today I had a bit of a headwind and got 75mph and climbing slowly before I had to slow for traffic. Is this expected for my size and weight? Bike has no windshield or fairing and is an "L" model, so there are almost no aerodynamics.

Enjoy the weather!
Dean

I'm 5'7" and 240 lbs so not as tall but almost as big a load. Mine was doing about the same as yours.

The best investment I made was a National Cycle Plexifairing III. The Suzuki dealer here got it for me for about $140 including shipping. Mine will now hit 85 mph with no problem but gets pretty slow to pick up speed above that. It sure makes riding, mileage, and speed a bunch nicer on the highway. The Plexifairing III is just the right height for me on my 550E. You're taller but the L model lets you sit lower so it might work for you too.

Just think of yourself as a big drag chute sitting on top of the bike. A windshield will help the aerodynamics a lot!

The best thing to do is to measure from the top of the headlight to just below your eye level while sitting on the bike. You measure from the ground to the top of the headlight and then sit on the bike and measure from the ground to just below your eyes. A second person will help. Most windshields tell you the height from the top of the headlight to the top of the windshield so you can tell if it is the right height.

[ddaum]

The best investment I made was a National Cycle Plexifairing III.

Great info Jimg, I will definitely look into getting one. Thanks!

[KEITH KRAUSE]

Glad you got the bike running well.