Announcement

Collapse
No announcement yet.

Cylinder 2/3 not Firing

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    Cylinder 2/3 not Firing

    I recently rebuilt my GS750 engine. I had a bit of a hard time getting it to start until recently the bike fires up right away. Last night it took it for a spin and it was running quite well until half way though the ride the engine lost most of the torque and seemed like it was only firing on 2 cylinders. Sure enough today I took a look at the plugs and inside the cylinder.

    Plugs 1/4 were a nice tan color and the cylinder inside looked dry. Plug 3 was pretty black and and the cylinder looked wet. Plug 2 was wet and the cylinder was wet as well.

    I tested the resistance over the coil I got a reading between 3.6 and 4.0 ohms on the coils. All 4 plus sparked and all 4 HT wires produced a spark. I am not sure if this would be an electrical problem / fuel problem / engine problem. One thing I did change before the ride was I put on the case cover breather filter and the hose is pretty long it sits on the pods of carbs 2/3. But with the breather venting air I would assume it would be lean not rich.

    I can definitely hear a back fire while riding and need to be at full throttle to really get any power. This all changed on me mid ride last night from having a well riding bike.

    Any ideas what it might be or what to check?
    Tags: None
    #2
    Electrical sounds OK (since all plugs spark). could be floats set wrong on 2 and 3. but since it ran OK and changed mid ride, I'd suspect a mechanical issue. What did you "rebuild" here? Check compression in 2 and 3- I hope it ain't the head gasket between them.
    1981 gs650L

    "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

    Comment

      #3
      Originally posted by tom203 View Post
      Electrical sounds OK (since all plugs spark). could be floats set wrong on 2 and 3. but since it ran OK and changed mid ride, I'd suspect a mechanical issue. What did you "rebuild" here? Check compression in 2 and 3- I hope it ain't the head gasket between them.
      Thanks Tom,

      I will double check the floats next week when I get back in town. I kicked over 90 psi on all cylinders but forgot to open the throttle so I will have to re do that. I am going to pick up a leak down tester and hope that will give me an indication of what could be wrong. I rebuilt the entire engine. New oil seals and piston rings. Honed cylinders. Lapped valves.

      The points for cylinders 2/3 had some white build up on it (carbon?) since I last adjusted them, so I used some fine sand paper to take that off. Is that an indicator of anything.

      I would like to upgrade to DYNA Ignition and coils but I want to make sure I fix the problem before I dump any money into it.

      Comment

        #4
        So I ran a leak down test and all cylinders are only at 5% so I did a decent job on the rebuild. But why are the cylinders not firing? Any ideas? I am going to dish out the money for Dyna coils and ignition and hope that fixes the problem when I get the next pay check. Stampede is really making it hard to save money haha and it just started.

        Comment

          #5
          Recheck the plug gaps and IF youve got a little extra wire, unscrew the caps and clip off about 1/4 inch and rescrew caps back on. Youll be amazed at what a nice fresh connection can do for it.
          MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
          1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

          NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


          I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

          Comment

            #6
            And whats the ignition?? Points and condensors or electronic? Condensors going south can make it misfire and stutter as well.
            MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
            1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

            NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


            I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

            Comment

              #7
              Originally posted by chuck hahn View Post
              And whats the ignition?? Points and condensors or electronic? Condensors going south can make it misfire and stutter as well.
              Thanks Chuck, they are points and condensers. All coils measure resistance well and fire. Not the best. I did see some white residue build up on the 2/3 points so maybe they are on their way out. Ill buy the new Coils, wires and ignition and hopefully that helps!

              Comment

                #8
                Originally posted by chuck hahn View Post
                Recheck the plug gaps and IF youve got a little extra wire, unscrew the caps and clip off about 1/4 inch and rescrew caps back on. Youll be amazed at what a nice fresh connection can do for it.
                I'll recheck gaps. I gaped them before the ride and it was running great then all of the sudden it craped out.

                Comment

                  #9
                  Sounds like I would be at the points and condensors first. Points shouldnt have any white chalky looking anything on them. Good sign that they may be shorting to ground. And burnt points make the gaps there larger also...which translates to ****ty running. See the manual here and note the trouble shooting section...

                  Page Not Found
                  http://www.mtsac.edu/~cliff/storage/gs/GS750_Service_Manual_early8valve.pdf
                  MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
                  1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

                  NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


                  I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

                  Comment

                    #10
                    Originally posted by chuck hahn View Post
                    unscrew the caps and clip off about 1/4 inch and rescrew caps back on. Youll be amazed at what a nice fresh connection can do for it.
                    I would definitely do this

                    Comment

                    Previous template Next
                    Working...
                    X