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    the best 650 engine options

    heres the two main things i know about the differences in a G model engine versus the E model engine other than what the rear wheel is driven by, the E model has a roller bearing crankshaft versus the G having a plain bearing crankshaft, and the E model has a larger intake camshaft than the G.

    I know I know I shouldn't put money into this bike but i think the only person that will be able to stop me is me, so id just like to know the best route going through with this, I plan on holding onto this bike for a very long time, possibly forever as its my first and also I spent twice the amount of money I bought it for learning how to fix it so this bike would never give me the money back I put into it regardless.

    the plan is to do a big bore kit bringing it from 670cc to 740cc, doing an intake mod and correctly tuning the carbs for the air increase, and completely going through the motor aswell as everything else to make sure I dont have any trouble down the road for a very long time since every little bit will be gone through all at once, id rather pay my dues now all together than little by little since i use this bike so much.

    i read back on an older post i put up and seen that the G model engine does make a little bit less horsepower than an E model and im sure the chain drive does have something to do with it but also having a larger intake cam does allow more air whether it being a taller or wider lobe, so i was thinking of putting an E model cam to help the motor breathe more.

    i guess my questions are would an E model camshaft be a direct fit onto the G motor, also would i be able to do the same to the exhaust cam or is that something that doesnt matter, and also would it be a better idea to go for a an E model crank or would that not help with anything performance wise. if theres a set of cams from a larger GS that could help increase power that would also be something nice to be informed about.

    i plan on completely tearing this motor down as the bike is going to be mechanically restored, i cant do the top end and add more power without making sure the bottom end is going to be okay.
    Ian

    1982 GS650GLZ
    1982 XS650

    #2
    The E is based off the 550. It's already got a big bore kit so to speak. The E cams use different sprockets than the G cams, otherwise they are very similar, so don't expect to make extra power by swapping.
    The G engines sometimes have crank problems, so that's extra points for the E.

    My advise is either which way, just focus on getting the bike running and looking really nice, then call it a day. Any modern 16V 600cc bike will blow a hot rod 650 into the weeds so why bother?
    Ed

    To measure is to know.

    Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

    Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

    Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

    KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

    Comment


      #3
      I don't plan on racing a modern 600 anytime soon, it's more for me just to satisfy what a young guy always want to do with a motor, make more power!

      Also it may sound a bit dumb considering I'm on a bike but really I'd just like to mess with cars lol, it's an old bike most people wouldn't expect anything to come out of it, especially since my bike has seen way better days, it'd just be fun to have this 40 year old survivor run brand new and also be faster than what it originally was, I love how this bike sounds screaming along the road, now only if it did it faster.

      Would the valve cover have to be changed due to a different size sprocket for the camshaft would you know?
      Ian

      1982 GS650GLZ
      1982 XS650

      Comment


        #4
        Also for the crank issue would welding it solve that problem?
        Ian

        1982 GS650GLZ
        1982 XS650

        Comment


          #5
          Going back and forth from here to one guy on Facebook, what I've learned is that I would need to only change the camshafts and not the sprocket because the crankshaft to camshafts ratio would be ruined as the sprocket is not the same size.

          Both the camshafts on the G would be swapped for the intake cams on the E model motor.

          So right now the base plan would be, doing a bore to the motor, doing an intake mod and proper tune on the carbs, and swapping the camshafts to allow a higher lift on the valves letting more air in aswell as letting more air out
          Ian

          1982 GS650GLZ
          1982 XS650

          Comment


            #6
            Can somebody confirm the 550E aswell as the 650E have the same camshafts? It's impossible to find the 650E camshafts but the 550 is plentiful.
            Ian

            1982 GS650GLZ
            1982 XS650

            Comment


              #7
              I don't know about specs. What I can tell you is that back when my 650E was new, it had a much better low RPM pull than my friends 550E. His bike had no grunt. Mine would pull from about 2000 RPM where his wouldn't. My 650E was cold natured but after I put in a Dynojet kit it wasn't cold natured anymore. I wouldn't put 550E cams in a 650E based on that.
              Dale

              1982 Suzuki GS1100G
              2017 Kawasaki Versys-X 300
              1999 Kawasaki ZRX1100
              1997 Honda 250 Rebel
              1984 Honda Nighthawk S CB700SC
              1973 Yamaha RT3 360

              Comment


                #8
                the reason i ask is because my only understanding (limited knowledge) is that the 650E is a bored out 550E, so i wasnt sure if that means they would have the same camshafts, i definitely dont want to do a downgrade though!
                Ian

                1982 GS650GLZ
                1982 XS650

                Comment


                  #9
                  Okay so, after a bit of research, I was able to find that the gs650e and gs650g/l have the same intake camshafts as they share the same parts number.

                  That being said, the E model still does have a different style crankshaft, what I'm wondering is if it has a longer stroke to it than a G model or if it would handle power better than the G model crankshaft.

                  All I plan on doing to this motor is a bore, and an intake mod with a correct tune for the carbs, the bore kit and actual machining will be right under $300 and then the intake mod plus the jets will probably be under $100.

                  The intake mod will have to be done regardless because my 1100-2500 rpm acceleration is complete *@%^$*@%^$*@%^$*@%^$e, if I put the stock pilot jets in and have the mixture screws turned out to their maximum setting I'm still learning out, if I go the very next size up on the pilots and have the mixture screws at their minimum setting I'm fouling plugs and losing plenty of power.

                  I know I'm not getting a big power increase, but I figured since I want to go through the whole bike and get it mechanically restored why not do some simple ways to add power, my exhaust cost about the same as the full bore mod will, and the intake in my opinion is a must as the exhaust isn't doing anything for the bike right now except make sweet noise and shedding off a bit of weight.
                  Ian

                  1982 GS650GLZ
                  1982 XS650

                  Comment


                    #10
                    Regarding the cranks - given that one's plain bearing and the other is roller bearing, they're not swappable.
                    ---- 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

                    Comment


                      #11
                      Originally posted by Grimly View Post
                      Regarding the cranks - given that one's plain bearing and the other is roller bearing, they're not swappable.
                      Learned a bit about the two lastnight, for what I'm doing to the engine it won't matter between the two luckily, just more oil changes lol
                      Ian

                      1982 GS650GLZ
                      1982 XS650

                      Comment


                        #12
                        found a gs650 intake camshaft for sale, first part of the build, hopefully next week i order the bore kit and start the teardown, happy to be doing this itll be a good refresh and will help me with my chopper build.

                        building an xs650 chopper btw, have a chopped frame and motor already.
                        Ian

                        1982 GS650GLZ
                        1982 XS650

                        Comment


                          #13
                          Does anyone see any downfalls in putting a intake camshaft on the exhaust side?
                          Ian

                          1982 GS650GLZ
                          1982 XS650

                          Comment


                            #14
                            Originally posted by timebombprod View Post
                            Does anyone see any downfalls in putting a intake camshaft on the exhaust side?
                            Most likely possible, if you know how to degree cams. The timing marks will be off so you'll need to figure out how to install them so that the cam timing is correct.
                            Do you know if the intake cam has more lift and/or duration?
                            '20 Ducati Multistrada 1260S, '93 Ducati 750SS, '01 SV650S, '07 DL650, '01 DR-Z400S, '80 GS1000S, '85 RZ350

                            Comment


                              #15
                              im not entirely sure whats exactly is the difference, i am getting a timing wheel to do it correctly, once the part gets here ill definitely be able to confirm what exactly is different, i believe its just lift but again not entirely sure so i cant guarantee
                              Ian

                              1982 GS650GLZ
                              1982 XS650

                              Comment

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