David Brown Tractor Forum

Hmmm. I think the explanation origins from the decision to produce cylinder block also to 990 without wet sleeves. The block has identical casting with 1200 but in order to keep that 990 in the 50..60 hp class it was rather simple way to limit the power by using shorter stroke. 1200 has stronger tra...

Hmmm. Are you sure that the small tap on the side of the injector pump is open? If its closed it will cause retarded injection and a lot of smoke.I have seen a tractor which suffered of smoky run all its life on a farm. The next owner turned the tap open and the problem was sorted. Unburnt fuel is g...

Hmmm When the hold valve plunger is off, the oli from the lift can flow freely to the lowering speed control valve. If the lowering speed knob is turned fully open the arms lif only very light objects, especially vhen engine idling. If the knob is turned fully in, the arms will lift rather heavy obj...

Hmmm. I have discussed with a fellow who had the same symptom. In his tractor the lowering speed valve is either stuck or the previous mechanic who has dismantled the valve chest has assembled the valve plunger to the bore upside down. This upside down sound stupid but I have seen that happen. Enery...

To get better access to the diff lock, its better to remove the flange, on which the oil seals are fitted. Use right size of bolts and a strong flat bar to the job, just in order to avoid the flange damages. To put the things back together you need a rod, slightly thinner than the drive shaft, on wh...

I have an 990 which has got the engine from a 1390. That means that swapping the engine between 1390 and 996 should be more or less a bolt-on operation. 990 has dual clutch but both stages on pedal, so I suppose my tractor has original 990 clutch assembly. I cant be sure if 1390 and 996 have interch...

I have seen one 990 (very identical fuel system with 996) which suffered of a dirt particle in the tank pipe. It did run a while but then stopped. After bleeding it did run a while again and stopped. The dirt was found after loosening the connection from tank line to the fuel line to the lift pump. ...

OK. Broken/disappeared 0-ring is probably the explanation. Now, when the pump is on desk, it could be a good idea to check if it needs new gasket rings. At least Dowty has replaceable seals which can give up and weaken the pressure output. I do not know about Plessey, but I guess that it has about t...

If your tractor has double acting valves on the RHS of the seat, they are independent of rear lift.

W.B.R erkki

As far as I know tightening the bearing is a simple job. The parts inside are rather robust, so they don't break up easily but still I think that investing a while for the job is the way to go.

There can be a few reasons to low pressure but first clean the by-pass valve on the valve chest. If the valve is clean, it is time to check the pump.

W.B.R erkki

Agree Olle,

I haven seen non-sychro gearboxes which have experienced lots of abuse with the result that the gear of 2:nd and 3:rd are worn out over half of their original width. The problem grows gradually when changing gears in move by crunching the rotating gears against each others.

RGDS erkki

Hmmm. 674 IH is close to same power class and weight class than 6711 Zetor. Maybe 1390 David Brown is about same size. It is very advanced tractor on PTO because of large variety of speeds. The rest of the tractor is conventional. 674 is rather agile with compared to 6711. Good luck.

W.B.R erkki

If the water level raises to level of cooling fan, it will certainly cause belt slip and in the worst case damage to the fan. Factory recommendations are true, of course. I know from experience that specific fuel consumption is higher when driving on the road by 2400 rpm with compared to 2000 or 180...

If the rear lift hold when the three way valve on th eleft hand side in in position "1" or "2" the ram piston seal is ok. The system has probably a leak in dump valve (if your tarctor has one, a stud sticking up on the cover just behind the main control lever) or the control spool valve. First aid t...