420 crawler hydraulic problem

Kws346 · Post by **Kws346** » Mon Mar 18, 2013 10:03 pm

I am currently fixing a 420 crawler that has been in our family for over 40 years. I think it is a 56 model. The crawler has been sitting for about 20 years with final drive and clutch problems. The final drives and clutches have been repaired and I cranked it for the first time in about 15 years last month. I have a problem because when I was testing the hydraulics the blade went up but will not go down. The hydraulic pump begins cavitating when the lever is pressed to go down. Anyone have any ideas ? The cylinders have been rebuilt and the valve assembly has been cleaned. When it was first cranked the blade would go down but not up. I reversed the hoses on the valve assembly and now the blade it stuck all the way up and will not go down. I would appreciate any help fixing this problem.

Kws346 · Post by **Kws346** » Mon Mar 18, 2013 10:19 pm

Sorry posted this question in the wrong section of the forum. First time to post should have read the instructions better.

Willyr · Post by **Willyr** » Tue Mar 19, 2013 5:55 am

sounds more like a valve problem and not the pump.

Post by **Lavoy** » Tue Mar 19, 2013 7:08 am

If it is a factory valve, it is a linkage issue. A 420 valve is two single spools working together to form two way hyd. If one plunger is not opening all the way, they fight each other, and the blade or whatever you are running won't work. Look closely at the valve as you operate it, both plungers need to move at the same time, and the same distance. Linkage and pin wear can be a factor too.
Lavoy

Kws346 · Post by **Kws346** » Wed Apr 03, 2013 12:20 pm

You were correct. I adjusted the linkage and now it works great. Thanks for the help.

Post by **Lavoy** » Wed Apr 03, 2013 7:08 pm

Good, glad to hear it.
Lavoy

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420 crawler hydraulic problem

420 crawler hydraulic problem

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