James Smith
New Member
I have a kobelco sk300lc. s/n ycu0795. There is an issue with the right track travel circuit, reverse direction only. The track will continue to advance even after the pilot (foot pedal) is released. This has been an intermittent issue until recently more so. Here is what I have diagnosed so far:
1) Removed spool from main control valve to inspect for scaring, gouging, broken return springs, etc. Everything looks great, spool seems to fit bore nicely. I even went as far as removing the spool form the left travel and swapped them out, Problem remains. Left spool is in same condition as right (problem) spool visually.
2) I switched pilot lines side to side. Right pedal controls left track, left pedal controls right track. problem remains.
3) Safety circuit... boom, stick, bucket, left travel all stop immediately when safety lever is lifted. Right foward will stop, however if right track is "caught" in reverse, lifting lever will not stop movement. Also, if Right is "caught" , moving foot pedal to forward direction will not "override" the reverse.
Basically the only way to stop the right reverse motion when "caught" is to wait it out and it will eventually quit, or.... if you shut the machine down and start back up, problem will not persist until pilot signal is initiated.
It seems like the right reverse pilot is kind of "locked" on. I do not currently have pressure gauges to monitor pilot pressure but am working on coming up with fittings and gauges to see what is going on there. Is there any way for that pilot pressure to get "trapped" in the line? and why would the forward pilot not override any residual pressure? MCV pressure bypassing internally to pilot side?
I am going to switch the forward and reverse pilot lines. I switched from left to right, but not forward and reverse so I guess ill try that still. Any other suggestions? Thank you in advance for any ideas!
1) Removed spool from main control valve to inspect for scaring, gouging, broken return springs, etc. Everything looks great, spool seems to fit bore nicely. I even went as far as removing the spool form the left travel and swapped them out, Problem remains. Left spool is in same condition as right (problem) spool visually.
2) I switched pilot lines side to side. Right pedal controls left track, left pedal controls right track. problem remains.
3) Safety circuit... boom, stick, bucket, left travel all stop immediately when safety lever is lifted. Right foward will stop, however if right track is "caught" in reverse, lifting lever will not stop movement. Also, if Right is "caught" , moving foot pedal to forward direction will not "override" the reverse.
Basically the only way to stop the right reverse motion when "caught" is to wait it out and it will eventually quit, or.... if you shut the machine down and start back up, problem will not persist until pilot signal is initiated.
It seems like the right reverse pilot is kind of "locked" on. I do not currently have pressure gauges to monitor pilot pressure but am working on coming up with fittings and gauges to see what is going on there. Is there any way for that pilot pressure to get "trapped" in the line? and why would the forward pilot not override any residual pressure? MCV pressure bypassing internally to pilot side?
I am going to switch the forward and reverse pilot lines. I switched from left to right, but not forward and reverse so I guess ill try that still. Any other suggestions? Thank you in advance for any ideas!
