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Old 07-10-2020, 07:49 PM
andyrob andyrob is offline
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Default JCB 802-4 mini-digger track idler tensioner problem


I've thrown a track and think I just need to release the grease valve on the idler unit and slide the idler/tensioner unit back so as to give me the required slack.

However, having done that I find the slider holding the idler wheel won't move at all and I don't want to use brute force, and a little ignorance, to move it back.

It could be that the grease-ram (whatever it's called) is seized - which is perhaps why when I've tried to take up the track slack in the past it's not moved - hence the thrown track.

Any suggestions please?

Last edited by andyrob; 12-10-2020 at 01:10 PM. Reason: SPAG
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Old 22-10-2020, 11:24 AM
andyrob andyrob is offline
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Default SOLVED: JCB 802-4 mini-digger track idler tensioner problem

Well, 255 views with no suggestions so far. It must be an unusual problem.

This (below) would also apply to the similar JCB 802, 802 Super and many other machines, I guess.

For the benefit of future readers it was the track adjuster/tensioner ram that had seized and so prevented the track form being tightened - which led to the track coming off its drive sprocket.

I ran lots of oil around the sliding parts that the ram is fitted to - in case they were seized into the main casing but that didn't solve it when I tried sledge hammers (on a wood block), ratchet straps around the track. (If doing this put the strap at 90 degrees to the run of the track, ie not round the track itself).

The simple solution was, first, to make sure the one-way (?) valve was removed (the part that the grease nipple which is used to tension the track is inserted).

Then, with the machine raised on one side, I ran the track very slowly and, as it turned, inserted a 1" round bar between the track and idler sprocket.
1" was big enough for me, I guess a bigger one might have been necessary if the track was slacker Also, perhaps I should have first used something like (softer) broom handle or similar - just in case the forces were hazardous using steel on steel.

This tightened the track as it rotated with the bar between the sprocket and the inside of the track. The ram 'gave' - and with such force that a large clump of grease shot from the ram, just like a paintball 'bullet'. It thought something like a bolt had hit me.

So, if/when you do this, make sure you're clear of the (removed) inspection cover where the valve/nipple has come from - or put the cover back on temporarily.

Last edited by andyrob; 22-10-2020 at 04:00 PM.
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idler wheel, mini-digger, tensioner, track thrown

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