Adjusting spool valve

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manxmac
Posts: 189
Joined: Thu Jul 15, 2010 5:49 pm
Location: United Kingdom I.O.M.

Adjusting spool valve

Post by manxmac » Sat Nov 09, 2019 2:08 pm

Hi
Having got my hedge trimmer lift ram fixed, new seals. I now find that my external spool valve kicks out just about every time I use the main spool block and I have to reset the spool valve handle forward or back from the mid neutral position. There is a sort of "nose" type extension on the spool block which looks as though there there could be an adjustable spring loaded overload valve in there. Is this the case and can they be adjusted?
Thanks in advance.
Manxmac

ALANJ
Posts: 55
Joined: Wed Oct 11, 2017 9:13 pm
Location: Co. Durham

Re: Adjusting spool valve

Post by ALANJ » Sat Nov 09, 2019 4:17 pm

The external valve you refer to is a Cessna double acting unit set to kick into neutral when system pressure exceeds ,from memory, approx 2,000 psi. This avoids system overload on the open centre system caused by blowing off of the main relief valve, the MRV.
The kick out setting can be adjusted by unscrewing the "nose" complete with spool ,then removing the circlip under the nose end cap and carefully stripping the detente mechanism.central to the detente is a small shim adjusted spring which governs the detente action via a piston and three detente balls.Adding shims to the original shim pack will increase the kick out setting to whatever the user requires up to the point where the systems max pressure will result in no kick out.
This adjustment procedure can be done in 30mins but requires a good working knowledge of the Cessna valve .
Hope this helps. AJK.

SteveCollett
Posts: 581
Joined: Wed Sep 24, 2008 8:17 am
Location: Suffolk

Re: Adjusting spool valve

Post by SteveCollett » Mon Nov 11, 2019 9:43 am

probably better to just tie the lever back possibly using a bungee strap?

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manxmac
Posts: 189
Joined: Thu Jul 15, 2010 5:49 pm
Location: United Kingdom I.O.M.

Re: Adjusting spool valve

Post by manxmac » Tue Nov 12, 2019 9:12 am

Thanks Steve.
Farmers fix will be my next try if that doesn't work I will have to get my grandson who is built like a racing snake to crawl under the cab and fiddle!!
Manxmac

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DB780
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Joined: Fri Dec 30, 2005 4:06 pm
Location: Lincolnshire

Re: Adjusting spool valve

Post by DB780 » Tue Nov 12, 2019 8:57 pm

You will find it easier to remove the valve completely, it's only those bolts and the lever. If you pull the spool out under the cab and the detent balls fly out you will never find them!

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