power loss after 40 MPH cutting out..HELP!!!

[cybersabor]

I have a 1981 GS550L it looks new and only has 10K miles on it.. but it sat for 13 years, it runs good but at about 45 MPH it starts cutting out and will only do 50 max and migh hit 6K RPM - im not sure what to do?..

 

[KitKat]

i would look at the valves, plugs, and do a carb cleaning.

http://members.dslextreme.com/users/bikecliff

use it ^^^ its amaazing


the cutting out, is it like the engine dies, then starts again, or is it bogging, where you can't accelerate after a certain point in the throttle?

 

[zacheriaj]

I have a 1981 GS550L it looks new and only has 10K miles on it.. but it sat for 13 years, it runs good but at about 45 MPH it starts cutting out and will only do 50 max and migh hit 6K RPM - im not sure what to do?..

Quite a few things you can check on. Im sure Basscliff will be on to tell you. But, Cleaned carbs? (Seperated, Dipped, Synched) is your exhaust stock? If not, are the carbs jetted for it? Pods or airbox? If pods, are the carbs jetted for it? Check to make sure the spark advance is moving freely. Fresh fuel? Any water will sink to the bottom and cause this sort of problem. Plugs bad or fouled? Valves adjusted correctly?. Clogged fuel filter? Filter at all? (could be restricting enough to not allow enough flow to keep up with high RPM.

Just to name a few... Good luck!

 

[tlepac]

And don't forget the O rings between the carbs and the cylinders heads..
Bet they are flat and hard as rocks and brittle

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. cybersabor,

Are there any mods on your bike like 4-n-1 exhaust or individual pod air filters? If so, your carbs might not be jetted properly. You might have a faulty petcock. Your carbs might not be properly clean. Do you have an inline fuel filter installed? Fuel filters can cause fuel starvation. Have you adjusted your valves? Have you checked your charging system and/or ignition system? Is your gas cap venting properly? After the starvation symptoms, when you open the gas cap do you hear a suction sound? In other words, there are a lot of things that have to be made right in order for a bike that's been setting for a while to run correctly. Don't forget to use the search feature in the forum. You'll also find a lot more info in my little "welcome thang"...

You'll find lots of GS lovin' on my website. Please stop by and feed your mind.

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. 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

 

[mike_of_bbg]

Thanks for posting cybersabor. Sounds like your bike has a case of GS-been-sittin-in-a-barn-for-13-years-itis. They don't like that very much. You need to restore your fuel system to pristine condition.

No worries though: with a bit of elbow grease and the expertise here, plus some parts and materials of course, you will get her running nicely. Did you completely clean and rebuild the carbs per the CV carb cleaning guide? If you have not, that should be your first order of business. Your carbs need to be very clean before real troubleshooting can begin (and if your bike is stock the cleaning will probably be the end).

Go to your local auto parts store to pick up a can of Berrymann's or Gunk carb and parts dip, a can of PB blaster, and a can or two of spray carb cleaner - oh, and some anti-seize too. Carb bodies and parts should be dipped for at least 12 hours, not the 20 minutes as noted on the can. Don't dip any non-metal parts. In your case, I'd pay some attention to the slides. are they moving freely? hold the diaphragms up to a bright light and look for any pin-holes. They must be replaced if there are any leaks. They're spendy but your bike won't run right otherwise.

(as noted by BassCliff - if you have any modifications to the intake or exhaust systems you need to post that! Pod air filters and high-flow exhaust systems require re-jetting.)

While your carbs are in the drink, head over to www.cycleorings.com and order your Mikuni carb o-ring kit, plus the intake boot o-rings and some stainless steel bolts to replace those soft, rusty screws holding the boots on. Resist the temptation to buy "carb rebuild kits", as there's probably no need to replace the jets and the kit jet quality may be sub-par. You might also pick up a couple of the tiny idle screw washers while you're there. They're easy to lose!

Now head over to z1enterprises.com and get your float bowl gaskets and carb pilot plugs. You might pick up some fresh fuel and vacuum line and an inline fuel filter while you're there. Oh, and a valve cover gasket so you can not leak after adjusting your valves (Maybe some half-moons too since those are probably pretty old).

While the carbs are off, check your boots (both sides of the carbs) for cracking. Replace any boots that might be leaking air. The carbs are designed to be run in an air-tight system. Any leaks will throw the pressure balance off and cause mixture problems (usually running lean, which can lead to burnt valves). Also make sure no critters have crawled up any where and built a nest.

Check your fuel petcock. First, there shouldn't be any fuel in the vacuum line. No fuel should run from the fuel line when set to "on" or "res", unless you apply some vacuum to said vacuum line (use a pump or your mouth but be careful). Fuel should flow in "pri" without vacuum. If your petcock fails any of these tests, replace it.

Finally, the tank should be clean and rust-free. Most rust tends to settle at the bottom of the tank, where we can't see it inspecting through the filler hole. Little chunks of rust can work their way down into your carbs and wreak all sorts of havoc. Search the forums to find a tank de-rust procedure that you like (I like evapo-rust).

Best of luck and let us know your progress! Think about adding your location to your user CP so we'll know where you are. Who knows, maybe you'll be a nice sunny-day ride away from some generous GSRer willing to lend you a hand!