jhandy Posted May 23, 2009 Share Posted May 23, 2009 Hello all, I have been trying to search the forum for help and finally figured I woudl just ask a question. 1981 xs400 special I cleaned the carbs and replaced float needles and o-rings. When I put the carbs back on it fired right up and idled good. I took it for a ride and when I pulled the clutch to slow down it died and would not restart, seemed flooded. Now it starts pretty easy but won't idle for long before it dies. Upon giving throttle it backfires and doesn't want to rev until it gets above 5000 RPM, then revs good above 5000. I took the plugs out and they were both black and one was grey at the very tip. I did find an exhaust leak on the right side so I will try ot fix that and see if it helps. Thanks in advance, this board is awesome!! Jesse Link to comment Share on other sites More sharing options...
JimR Posted May 23, 2009 Share Posted May 23, 2009 Hello all, I have been trying to search the forum for help and finally figured I woudl just ask a question. 1981 xs400 special I cleaned the carbs and replaced float needles and o-rings. When I put the carbs back on it fired right up and idled good. I took it for a ride and when I pulled the clutch to slow down it died and would not restart, seemed flooded. Now it starts pretty easy but won't idle for long before it dies. Upon giving throttle it backfires and doesn't want to rev until it gets above 5000 RPM, then revs good above 5000. I took the plugs out and they were both black and one was grey at the very tip. I did find an exhaust leak on the right side so I will try ot fix that and see if it helps. Thanks in advance, this board is awesome!! Jesse Hi Jesse, I guess the carbs need some more work.. sohc XS400's were just a bit odd with regard to their carbs Regards Jim Link to comment Share on other sites More sharing options...
jhandy Posted May 23, 2009 Author Share Posted May 23, 2009 It ran better before I took the carbs off. It doesn't leak gas through the airboxes anymore, which is good. Is there something I may have misadjusted when I had the carbs apart. Is the air mixture screw the thing under the black rubber plug? Should that not be screwed in all of the way? Thanks, jesse Link to comment Share on other sites More sharing options...
chopped850 Posted May 23, 2009 Share Posted May 23, 2009 Most carb air screws are 1 1/4 to 2 turns out. Seat the air screws lightly and back them out 1 1/2 turns and try that. Are both slides opening at the same rate and time? You might also want to make sure the pilot jet's and choke circuits are free and clear. Link to comment Share on other sites More sharing options...
plain old dave Posted May 24, 2009 Share Posted May 24, 2009 Random thoughts: -How are your carb boots? Unless they are PERFECT, they can cause weird things to happen. -Float level? -Initial timing? That spitting back might be a timing issue. Link to comment Share on other sites More sharing options...
JimR Posted May 24, 2009 Share Posted May 24, 2009 It ran better before I took the carbs off. It doesn't leak gas through the airboxes anymore, which is good. Is there something I may have misadjusted when I had the carbs apart. Is the air mixture screw the thing under the black rubber plug? Should that not be screwed in all of the way? Thanks, jesse Hi Jesse, the mix screws are under the rubber plugs ... with there adjustment you must be quite careful as the point of the screw is very fine and if screwed down to tight (to start the adjustment) the points can break off. To set them ensure that the valve clearence, ign timming/dwell & carb balance are correct, with a warm engine screw them in and back them out about a turn or so then just adjust them slightly until you get an even tick over and when load is applied to the gen (turning the lights on perhaps) the idle speed doesn't drop. If the screws are broken you have a problem as the broken off bits are near impossible to remove from the carb bodies Regards Jim Link to comment Share on other sites More sharing options...
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