1980 GS 550 no power after 60mph

[bodcherokee]

I got my first bike out of a barn were it sat for 10 years or so as a foot stool. Great condition just missing carbs. It is a 1980 GS550L. I bought a donor bike for the carbs, it was a 1980 GS550E. I got the L running and it is great in the city but once you get up into 4th 5th and 6th gear it is a dog. You cannot rev it past 4500 rmps in 5th or 6th and it wont go over 60 mph. If i hold it at 60 for more than a mile, when i slow down, it dies. I'm guessing it's a fuel issue but i have completely cleaned the carbs and i have the stock air box on with no leaking. Any help is appreciated, thanks.

[Suzuki_Don]

Hi. Welcome to the forum.

Did you give the carbs a proper clean?

Did you disassemble each carb completely and dip each carb individually in Berrimans as required?

Did you replace all "O" rings inside carbs and also boot "O" rings?

Are there any air leaks from old hardened boots on airbox side and engine side of carbs?

Does the petcock flow enough fuel?

Is the tank breather blocked?

Is float level set correctly?

Just some of the questions that need to be asked.

[mike_of_bbg]

The dying after a minute sounds like bad venting of the gas tank. The next time it dies, try popping the gas cap off and see if it starts right back up. Might also check the petcock screen for gunk. Do you have an inline filter installed?

Silly question - are you removing the choke as it warms up?

[cowboyup3371]

When you "cleaned the carbs" did you completely disassemble each one, dip the bodies in Berryman's carb cleaner for 24 hours, replace the orings, spray out each orifice and run a thin wire through the jets, bench synch, adjust the valves, and vacuum synch? Were the intake boot orings replaced (at least)? Are you running pods or stock filter?

Welcome to the forum. Each of these questions are going to be answered for you in the site and info you'll get from Basscliff. Be sure to run through the maintenance procedures correctly or you'll continue to have issues.

Where are you located? Through that in your profile and your bike info in your signature block and there might be one of us close enough to help.

[BassCliff]

Greetings and Salutations!!

Hi Mr. bodcherokee,

Have a good look in the links below for all of the maintenance procedures necessary for a 30 year old motorcycle.

Now let me dump a TON if information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[IanDMacDonald]

This is a really common issue, with power loss at top end. However, the solution is not so exact. My Yammie had this issue, and it had to do with the junk Emgo pod filters I had on the Mikuni carbs. They were reducing the airflow to the point where there was powerloss. I threw on some K&N's and re-jetted properly, and see a nice redline rev, and speeds in excess of 100 miles an hour (I avoid it as the Yammie stock front end rides like a bent paperclip at those speeds). I think you would be okay with guessing it's either a fuel or air intake issue. Make sure your airbox is sealed, your carb boots are good, all o-rings replaced (including intake o-rings), and carbs are jetted properly. Don't try and tackle it all at once. Work on one area at a time and isolate the problem. I'd work from one end to the other to eliminate the problem. Start from the airbox and work towards the engine.

[pete]

Does it go past 4500RPM's in any gear?

I wonder if it's the advance mechanism? Take the timing/ignition cover off the right case and give the rotor a twist with your fingers.

If it doesn't move easily, that could be the problem...

[Hornswaggle]

Just tossing this out there but if it was a barn bike for 10 years could the exhaust be plugged (mouse nest, etc.) and cause something like this? If it didn't have carbs something could have gotten in that way and made its way through and caused a partial obstruction.

[bodcherokee]

Thanks for all the info everyone. I have heard from a few people to pop the side cover and advance the timing. It has the stock air box on it and i'm thinking of getting a set of cones. It doesn't rev past 4500rpms just like you said too. I'm also looking on advice on rebuilding a my 550 engine. I have the one off my donor and i have rebuilt car engines but never a motorcycle one. Anyone know where i can get parts and gasket sets? Thanks again, love these kinds of forums, i build jeeps and i use those forums all the time. Better than any haynes or chilton book you can buy and this is free.

[cowboyup3371]

Basscliff should be along later to give you his official welcome which includes links to many parts suppliers. Most of us use boulevardsuzuki.com, z1enterprises, and Gssuzuki.com among others.

[tkent02]

What's your location?

I could trade help with your 550 for some help with my Jeep.

Unless you live somewhere else.

[bodcherokee]

Basscliff should be along later to give you his official welcome which includes links to many parts suppliers. Most of us use boulevardsuzuki.com, z1enterprises, and Gssuzuki.com among others.

Wow thanks, that z1 enterprises has a complete engine gasket set for $67, thats great.

[tkent02]

Steer away from aftermarket stuff for the head and base gaskets. Why does the engine need to come apart? Does it have low compression?

[mike_of_bbg]

Thanks for all the info everyone. I have heard from a few people to pop the side cover and advance the timing.

That might help some. If the ignition is still stock you'll have to cut or drill some new holes or slots to advance the timing I think. I'm betting more on carbs.

It has the stock air box on it and i'm thinking of getting a set of cones.

That's not likely to help in the short term (or, probably, the long term either). Three bits of advice you'll see frequently about Pod filters and CV carbs:

1) Only use good quality Pod filters (read: APE or K&N, no Emgos).
2) Don't do it until you get your bike running well with the stock airbox.
3) If you go with pods, get a Dynojet kit.

It doesn't rev past 4500rpms just like you said too.

To me, you really need to establish a base line before you go much further. Some thoughts:

1) You said you cleaned the carbs - was that a full 24-hour soak per carb as per the GSR guide? Generally we recommend that, and an overall o-ring replacement. Don't bother with rebuild kits; the machining of their parts is generally inferior to what you find in the stock parts. Sometimes people need to dip 'em twice before they're really clean. Spray carb cleaner just isn't going to cut it. You also need to verify the proper float level, and make sure the slide diaphragms are completely free of leaks.

2) Have you verified the adjustment of the valves yet?

3) These GSes are set lean from the factory, and are VERY sensitive to any intake leaks. The O-rings on the carb boots are common culprits. The boots themselves may be over 30 years old. Before the carbs the boots need to be in good shape and the airbox well sealed.

4) I take it you've verified spark on all four plugs? Try a resistance check with your ohmmeter between the plug caps on 1-4 and 2-3.

If you start the bike up and idle, do all four pipes get hot?

[tkent02]

Someone earlier said to check for a clogged exhaust, have you done this? It is by far the most likely problem.