hitachi EX 120-1 main pumps valve plate stuck in high travel mode

[ace of spades]

Hi everyone, I have a EX120-1 with a problem to do with the hi speed travel. I think the main pumps valve plate is not destroking by itself causing it to not travel in low speed. Im unsure what the pressures should be in the pilot hoses from the control valve to the top cover of the pumps. Has anyone else seen this issue where the valve plate is not going to maximum stroke ?
Thanks in advance for any help ,this has become quite a nightmare about lifting my track every which way i turn :Banghead

 

[rmllarue91]

Hi ace
I don't have much experience with this particular machine but I have some basic information that might help. The main pump should consist of two sections they should be load sensing. Travel motors should be variable displacement Motors. I guessing you have a switch in cab for high/low. Witch should control a solenoid on a oil manifold. oil from the manifold should change the angle off the swash plate change the stoke of pistons in travel motor. This will increase speed of input speed into finale drives increasing travel speed.
Does machine stall if you hold any functions against relief valves( hold function at end of travel)

 

[fiathitachi130]

A 120-1 has three solenoids beside the main pump. two of these are used to control engine rpm, the third solenoid is used to change the max flow of the pump.This only changes from 110 l/min to 120 l/min depending what work mode and travel mode are selected Different travel speeds on this machine is only achieved by different engine rpm. You,r final drives/ travel motors have a fixed squash plate. I have a similar machine an this baffled me for some time.

 

[ace of spades]

Hi and thanks, Yes dipper arm out gets very slow and nearly stalls motor by furthest reach.