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Bandits '77 GS750 Revival

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    #31
    If the battery's down enough to just about crank the engine but not supply suffienct oomph to the points or ignitors, it won't start.
    This problem was common enough back before a 77 bike or car.
    ---- Dave
    79 GS850N - Might be a trike soon.
    80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
    79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
    92 XJ900F - Fairly Stock, for now.

    Only a dog knows why a motorcyclist sticks his head out of a car window

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      #32
      Originally posted by allojohn View Post
      It's the CV carbs that can flood the engine - VM carbs flood out the back of the carb into the airbox or pod. You're safe.
      Gotcha, thanks for the clarification.
      - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
      - 1977 GS750B - Sold but not forgotten

      Comment


        #33
        Originally posted by Grimly View Post
        If the battery's down enough to just about crank the engine but not supply suffienct oomph to the points or ignitors, it won't start.
        This problem was common enough back before a 77 bike or car.
        Maybe that was the issue then.
        - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
        - 1977 GS750B - Sold but not forgotten

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          #34
          Just a little update for you guys, or rather compiling the information into the build thread.

          I got a shim stuck in the bucket when adjusting valves and had to wait on some engine parts so decided to work on something else.

          The brakes are locked up so I disassembled the front and rear calipers. Carefully unstuck, cleaned and polished the piston and bore with 0000 steel wool, but when I got ready to order seals and pads, I discovered they were outrageously priced and difficult to find for the front caliper. So looked around for newer calipers in better shape that I could swap on. Purchased a set from Burque73 and they arrived weeks ago but haven't had a chance to dig into them yet so I'm not even sure they fit, but the GS Hive mind seems to think there's a good chance they will.

          I've got a few other projects in the garage I hope to wrap up in the next few weeks and then I plan to get back on the 750.

          The short list I plan to attack once I get back on the 750 is to sort out the brakes by:
          -Master rebuild/cleaning
          -New brake lines
          -"new" calipers installed (hopefully they fit and don't need rebuilt but we'll see)
          -new wheel bearings

          I think once I get brakes and wheel bearings done I'll get back to engine work. My plan for now is just to get it back on the road for this season. I think with brakes and getting the engine sorted, I can ride it this spring. We'll see how it goes.

          Oh, definitely going to need some new tires too. They're hard and dry rotted so I'm not going to take a chance on them.
          - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
          - 1977 GS750B - Sold but not forgotten

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            #35
            Had a chance to work on the 750 last night.

            I finally got that stuck shim out, and it was a pain. Tried a blast of air, two magnets, sharpened tiny screw driver, razor blade and heat but it would not budge. So I pulled the cam chain idle sprocket and the exhaust cam bearing caps and carefully moved the cam enough to get the bucket out. I kept the cam sprocket engaged with the chain as I moved it, and kinda rolled the cam in the chain to walk it over far enough out of the way in an attempt to keep it in time. With the bucket out, I tried all the same methods again and it still would not budge. So then I put the whole thing in the freezer for a while, then quickly heated the bucket and tried to tap the shim out. STILL STUCK... So at that point I'd been messing with it for hours and was getting frustrated, so I stuck a small screwdriver in the window and started tapping harder than I probably should have with a small hammer. Finally started to move and after some prying and generous tapping it came out.

            I put in a 2.55 shim and now clearance is 0.125mm. It's too much per spec, but I don't have another 2.6 shim on hand. I think it'll be OK? What do you guys think?

            I put the new cam cover back on with a new gasket so engine is all back together after triple I checked the cam timing per the manual. I think engine work is done and ready for the carbs to go back on.

            I also checked the 82 650G front L brake caliper on the bike and it fits like a glove! So next I plan to continue working on the brakes.
            - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
            - 1977 GS750B - Sold but not forgotten

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              #36
              Brakes are done for now. I "rebuilt" the master cylinders and calipers buy disassembling and thoroughly cleaning. Was able to reuse all the seals and boots. Decided to replace brake lines at a later date when I do a proper rebuild. For now the bike will just be for around town so I'm not concerned about the brake lines that are on it. Flushed them well until fluid came out clear, and installed the calipers and bled them.

              Also installed the carbs and throttle cables.

              All I need to do now before a test ride is front wheel bearings and carb to airbox snorkels. Hopefully will be ordering those this evening or tomorrow.
              - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
              - 1977 GS750B - Sold but not forgotten

              Comment


                #37
                Originally posted by Rob S. View Post
                Lose the crash bar!
                I'm sure you'll be happy to hear the crash bar has been removed. Had to take it off to get a vice grip on the head to hold the cam down when reinstalling. As I was taking the bar off, I thought of you and how proud you would be.
                - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                - 1977 GS750B - Sold but not forgotten

                Comment


                  #38
                  Was able to get more work done on the 750 today. I installed new front wheel bearings and put the bike back together for a test ride. Still waiting on several parts (petcock rebuild kit, new airbox snorkels etc.).

                  Here's a few pictures from today.

                  Front wheel off for bearings.


                  Back together and ready for a test ride. Notice the "new" front caliper courtesy of Burque73.


                  Aaaaaand, out side warming up for a quick ride.
                  Last edited by 93Bandit; 02-26-2022, 09:16 PM.
                  - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                  - 1977 GS750B - Sold but not forgotten

                  Comment


                    #39
                    I was able to ride it down to the end of my street and back. Maybe 1/2 a mile. It was really cold so I didn't want to go far, just far enough to get through all the gears.

                    It ran through all gears, cruised well at 50mph, but it's still not running right. Some backfiring through the carbs, falls on it's face if you whack the throttle to WOT, and it has an erratic idle that sometimes hangs at 3k rpms. It acts like it's getting air somewhere, but I have no clue where. It's got new OEM intakes with o rings and I ran it with the airbox on. Is it possible my pilot jet and air screws are causing this? Seems unlikely to me, they're all at the base 1 turn out setting.
                    - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                    - 1977 GS750B - Sold but not forgotten

                    Comment


                      #40
                      Worked on the bike some more today. Installed the new airbox snorkels and air filter which were the last original components on the air/fuel side. I thought that might fix the hanging idle but it didn't seen to, although it is better than before. Adjusted the idle air screws on all 4 carbs but they didn't seem to do much. The idle is still unsteady/erratic. There some popping from the exhaust at idle as well. Took it for another ride around the block and it ran better than last time, cruised really well and accelerated pretty hard too. But every time I came to a stop the idle was hanging around 3-4k. Adjusted the idle screw and it settled at 1100 but after more riding it would start to hang again.

                      Not sure what's going on. I checked compression with it hot. 150, 140, 140, and 145. That seems pretty healthy to me.

                      Any ideas guys? I'm kinda at a loss at this point on the idling issue.
                      - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                      - 1977 GS750B - Sold but not forgotten

                      Comment


                        #41
                        After sleeping on it, I recall it was difficult to start when hot, it would crank a while before finally firing and it would stumble quite a bit. When I gave it a little choke, it fired right up so that makes me think I have the pilot jets too lean. They're 1 turn out, but maybe they should be 1.5 or so. I'll turn them out a little more and then see if that helps the idle air screw adjustment.

                        Also, I didn't adjust the slides at all, they're at the factory setting. Figured they'd be fine where they are, but the bike has 18k miles so it's probably due for a balance. I'll try these few things and see what happens.

                        On a side note, after running it a while I noticed a substantial amount of smoke coming from the head at cylinder 1. The engine is oily everywhere, but especially there. It never burned off and stopped smoking so the head gasket is likely leaking faster than I expected. A full rebuild will be necessary sooner than expected. I won't have the time to get into it that deep this year since baby #2 is due in April. Maybe that'll be next winters project.
                        - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                        - 1977 GS750B - Sold but not forgotten

                        Comment


                          #42
                          A vacuum sync will make a massive improvement... beg, borrow or steal a Morgan carbtune. 1 turn out on the fuel is right, air jets should be half a turn either side of 2 turns out - and each jet could be different.
                          -Mal

                          "The only reason for time is so that everything doesn't happen at once." - B. Banzai
                          ___________

                          78 GS750E

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                            #43
                            Thanks for the info. I thought I had read the air screws would be ~2 turns out. I'll have to double check.

                            I actually have a Morgan carbtune, recently purchased it. Haven't had the chance to use it yet but this will be a good excuse. I'll try to balance the carbs next, then maybe fiddle with the pilot and air jets again if needed.
                            - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                            - 1977 GS750B - Sold but not forgotten

                            Comment


                              #44
                              So we had one good 58 degree day and now it's cold again. I'm getting impatient and can't run the bike outside to tune the carbs because it's so cold. So, I've had an idea for a while now and finally decided to try it.

                              The previous owners of the house were growing the devils lettuce in the garage and they put a fan in the wall of the garage that blows out. I was trying to think of a way to use it until I take it down and patch the hole. I repair a lot of small engines in my garage and always wish I had a place to run them in the winter months since it gets so cold here. I've ran stuff inside for short periods of time, but never long enough to get to operating temp and tune. I bought some ducting and some dryer vent hose. I used the regular flexible vent hose (rated for 180F) from the fan to the Y section, and the more rigid vent hose from the Y to the exhausts (rated for 450F). So far it's working really well. I ran the bike up to operating temp and the hoses never got too hot to touch and the garage didn't smell like exhaust at all. So I think it'll work out well enough for small engine stuff. Hopefully it holds up over time.

                              - 1983 GS850L ~ 30,000 miles and going up - Finally ready for a proper road trip!
                              - 1977 GS750B - Sold but not forgotten

                              Comment


                                #45
                                That's a fascinating way to do it. I gotta keep that in mind.
                                Charles
                                --
                                1979 Suzuki GS850G

                                Read BassCliff's GSR Greeting and Mega-Welcome!

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