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Quick Carb question '77 550E

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    #16
    Adjusted the valves?

    Synced the carbs?

    Completely cleaned the carbs? (yes, I read this thread) that pilot fuel screw controls idle mixture, where did you set it?

    Definately not the coils or plugs

    Hmm, let's check on your progress- yep, #1, #2,#3

    1A) (NEW) Trying to diagnose running problems on a bike with an unknown maintenance history is an exercise in futility until a baseline is established though proper maintenance. Things like clean carbs, properly adjusted valves, sealed intake system (airbox, carb boots), a clean gas tank (no rust), and a properly functioning petcock are 100% mandatory for the bike to run properly. It's best to perform all the bikes maintenance when you first get the bike, and then if problems show up you will know what the problem is not.

    1B) Incomplete carb cleaning. A proper carb cleaning requires a full tear down, soaking the parts in carb dip, and reassembly with fresh O-rings (cycleorings.com). Pilot jets, choke tubes, and pilot circuit passages in particular need a proper cleaning before the bike will run right. Even if the bike seems to run right, if the O-rings are original they are sure to be hard and brittle thus problems could be right around the corner. This is a link to a carb tutorial that you may find useful... http://www.mtsac.edu/~cliff/storage/...d_Tutorial.pdf

    2) Not replacing the intake boot O-rings. The classic "hanging idle" is often traced to this simple fix since air gets sucked past the old O-rings and into the engine causing a lean condition. Most GS bikes have these O-ring, but not the 2nd generation 750 or 1100E family. While you are at it, make sure the entire airbox system is 100% sealed, since drawing false air into the system will increase running temperatures and make the bike run poorly.

    3) Not adjusting the valves. The valves tighten with mileage, and once all the clearance is gone the valves hang open which not only results in poor running but damages them as well - burns them. If you wait for your bike to misbehave before performing this critical maintenance, you may damage the engine.

    4) Trying to run the bike without the airbox...or installing pods, or a header, w/o rejetting. The air/fuel ratio will be drastically lean, which will not only cause running problems, but likely damage the engine too by causing it to run hot. Installing a free flowing exhaust will likewise change the jetting requirements, but not as drastically as pods.

    5) Ordering "carb kits" full of inferior aftermarket jets. A new O-ring kit from cycleorings.com is all that's necessary most of the time. Get some new float bowl gaskets and pilot jet plugs if necessary from a place like Z1 Enterprises to supplement the O-ring kit.

    6) Trying to clean out the brake system full of brown gunky fluid by flushing the system. If the fluid is dark and brown the only way to clean the system is a full tear down and clean out otherwise chunks will remain behind in the system. While your at it the old rubber brake lines should be changed. Suzuki call for replacing the lines every 2 years, so if your bike still has the originals you are 28 years overdue. The old lines will lead to spongy brake lever feel and contaminate the fresh fluid you just installed.

    7) Waiting for the charging system to fail, instead of cleaning up the old wiring. Many a battery have been boiled dry after the grounds corrode. Running a dedicated ground to the battery, or a solid frame attachment point, is strongly advised. Suzuki also botched the stator wiring by routing one leg up to the now discontinued head lamp switch. This needless wire path often overheats and damages the harness in the process. Do yourself a favor and rewire your charging system: run the stator wires directly into the R/R, make sure your R/R has a solid battery or frame ground point, and run the positive (power) R/R output either straight to the battery (with 20A fuse in-line) or though the regular fuse block after you check for resistance in the circuit and repair as needed.

    8) Using the wrong oil and/or gasoline. Auto oils have less zinc and phosphorus (high pressure additives) than they used to since the EPA has mandated reductions to protect catalytic converters. Motorcycle oils are fine but expensive, and even motorcycle oil has reduced additives these days. Diesel engine oil is cheap and contains lots of high pressure additives appropriate for our engines. Shell Rotella oil is even certified for use with wet clutches if that makes you more comfortable, although just about any diesel oil is fine. As for fuel, Suzuki calls for use of Regular gas. Using Premium provides no positive benefits for your bike and is more expensive.

    9) Search out the information about your upcoming wrenching tasks before going off unprepared and possibly damaging something. Search using "Advanced Search" and then click "Titles Only" to quickly hone in on the topic at hand. Almost every possible question a newbie could ask have already been answered. For example: there are tons of threads on how to avoid broken exhaust bolts and float posts. Sadly, most newbies learn these tricks AFTER they damage their bike.

    10) Buying a 30 year old motorcycle because it was cheap without any mechanical knowledge and no interest in learning. Paying a shop to work on your 30 year old motorcycle is not advised unless you have lots of money to spend and know for a fact that they are trustworthy.
    1978 GS 1000 (since new)
    1979 GS 1000 (The Fridge, superbike replica project)
    1978 GS 1000 (parts)
    1981 GS 850 (anyone want a project?)
    1981 GPZ 550 (backroad screamer)
    1970 450 Mk IIID (THUMP!)
    2007 DRz 400S
    1999 ATK 490ES
    1994 DR 350SES

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      #17
      Background to bike maintenance etc...

      Many, many thanks for the response, love this site so much, reply attached...

      1A) Bike was running well, except would run out of puff at about 20 miles, like it was running low on gas. Cleaned out tank, petcock etc now will run for many miles.

      1B) I followed the cleaning procedure and 'bench' synced the carbs as per the guide. I didn't renew the pilots screws (as #2 was seized in), but did clean out all the passages with carb cleaner and a wooden dowl where I thought safe. All floats set to 24mm as suggested in manual.

      2) I will check that all the Pods are correctly seated as I removed them and they are a bit tight to fit.

      3) It could be the valves as the bike had not been ridden much in the past 10 years while it was off the road. I have since put 800 miles on it.

      4) It has pods and a 4 into 1 exhaust, jets are now 97.5, stock should be 80 for this.

      5) Fitted new float bowl gaskets and checked the wear on the float needle valve which was within limits.

      6) New brake master cylinder, steel line and pads since I bought it, front is almost as sharp as my R6!

      7) I have a new battery and connect it to a refresher when not in use. I also have an old car battery which I hook up to it when trying to get her going. Wiring is good but will check R/R earth and the associated wire to the headlamp. As it was running ok, may have already been done or otherwise, ok.

      8) I have put diesel engine oil in it as I have loads of it hanging around for my diesel car, same SAE rating. Didn't realise at the time it was better for the engine!

      9) Sorry if these issues have already been discussed elsewhere.

      10) I have been riding for 20 years now and started out on old rotters making the majority my mechanical mistakes on those. Since finances have improved I have had more modern bikes and maybe lost some skills.

      As post script to this, I have very clean plugs on cylinders #1, 3 and 4. #2 has black soot on it. It is the one carb that I could not adjust the pilot screw on. All other pilots are set at 2.5 turns. I am guessing this is the root of the problem?

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        #18
        The first step in tuning up one of these old bikes is to do a proper valve-adjustment. Everything else follows that. Do it correctly, or you will spend forever chasing problems.

        As far as the carbs, a complete disassembly, dip, and thorough cleaning is absolutely necessary. You can't half-ass it and expect good results.
        Last edited by Guest; 10-19-2012, 11:54 PM.

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