Hi there,
I have recently purchased a david brown 880 white version. I have a fair bit of experiance with rebuilding tractors and I am currently training to be an engineer at college. My question is – I have purchased an engine rebuild kit for this 880 but I could only get one with unfinished liners! Do you have any idea
how to (finish them off?)

Any help id be greatfull

Matthew

Hi Matthew,

If they are the dry liners, then when the liners are squeezed in (sometimes this takes some force) the diameter of the bore will change slightly. Therefore they need to be finnished to the correct size, and then honed.

To do this you need a honing machine. The best job is to take it to an engine machine shop as they have a proper machine to do the job. The machine also leaves the correct hone (diagonal) grooves in the bore.

You can get honing tools which fit to an electric drill, but these are definately not to be recommended – in fact DO NOT DO IT. These tools do not leave a perfect bore.

The reason for the honing marks is to trap oil in the grooves of the liner, which lubricates the rings, without allowing excess oil consumption – so it is a controlled lubrication system.

During the honing process, the bore diameter must be checked regularly for roundness and eveness up and down the bore. This is measured with a bore comparitor (the bore comparitor doesn’t take a measurement as such, but indicates the deviation from a set measurement).

So, you will need to go to the engine reconditioning shop. Maybe they will
show you the process. The picture below shows the cross-hatched hone marks in some cylinder liners.

Steve.

Hi there,

I have recently purchased a David brown 880-selectamatic 1966 white version. I have a fair bit of experience with rebuilding tractors but this has baffled me, can anyone help me to solve this problem, I have placed a post knocker onto the external hydraulic pipe system on the back of the tractor, but once all the correct valves have been opened and the rear hand leaver dial aimed to external t.c.u. nothing happens apart from a slight twitch from the pipe. The oil admitedly was slightly creamy as water must have entered from running down the gear sticks, so oil and filters have been changed, another David brown tractor has easily lifted the weight on the post knocker, so that is working ok, and I have lifted a tipper trailer with the external hydraulics ok but with a slow return. The pump pressure has been checked, and with some revs read 1600, so, what do you think the next area to check is,

Thanks,
Ken Coppice

Hi Ken,

Obviously the hydraulics do work because you have tipped a trailer. Could it be that the hydraulic couplings are not opening each other???? Try new couplings or hard piping the post knocker to the tractor to see if that solves the problem. I know this doesn’t seem like a particularly technical suggestion, but it just may be a simple thing like this that is causing you problems.

Regards,

Steve VTE