500 Classic UCE oil supply issue
Posted: Thu Aug 20, 2020 5:44 am
In an earlier topic I reported about a ticking sound from the valve drive in my 500 classic UCE and how I tried to fix it. It was a long process with ups and downs, and the question was why so many UCEs have the same problem. There must have gone something wrong in the factory. Here are my findings and one possible solution for the basic problem:
The factory oil pump has the output O-ring fixed with superglue to the output stud. The O-ring material is not of a good quality and will not withstand the influence of the superglue. The superglue will penetrate the material and it will become brittle. As the superglue is not flexible, but adheres very good to the O-ring the O-ring will no longer be flexible but hard and when compressed will show cracks.
The oil pump is die-casted and the surface where the O-ring is placed is rough. On such a surface an O-ring cannot seal a joint.
The O-ring is placed between the oil pump output stud and the RH engine cover. Here, the surface is machined and plain. When placing the engine cover and tightening the screws the O-ring will be compressed and seal the joint between the oil pump stud and the oil filter compartment’s input whole – so far the way it was thought by the constructors.
This may be fine as long as the gap between the oil pump stud and the engine cover is correct, factory tolerances are small, the O-ring is of a good quality and the screw holding the engine cover will be tightened with the correct torque.
One important factor in the game are the gaskets between the oil pump body and the crank case as well as the gasket between the crank case and the engine cover as they determine the cap between the oil pump output stud and the plane where the O-ring has to seal the gap. The engine cover gasket as installed by the factory has a thickness of 0.4mm. The replacement gaskets our host offers have a thickness of 0.7mm, resulting in a gap that is 0.3mm larger. That makes the oil supply problem more serious as the O-ring will be more prone to leakage.
In view of this facts, the factory solution is very poor, as a leakage in these place will reduce the overall oil pressure and oil amount in the whole engine where the rocker bearings are the most sensitive ones. A reduced oil pressure and oil amount may lead to an insufficient lubrication of the rocker tips, too. The result will be a heavy wearing.
For a permanent fixing of the problem I recently ordered a new oil pump and converted it. The first step was milling off the top of the output stud with the O-ring recess and the rough surface to have a plain surface. Afterwards, the inner diameter of the stud was enlarged and a thread M12x1 mm added. Next, I machined a stud that carries an O-ring at the bottom end that is screwed-in in the oil pump. The O-ring seals the joint between the stud and the oil pump housing.
The stud has a flange on its opposite end, also carrying a (thicker) O-ring. The heights of the flange surface is the same as the O-ring accommodating recess on an factory oil pump. The lager cross-section of the O-ring will be more tolerant to differences in the thickness of the engine cover gasket. As the stud end is longer, it will lead through the O-ring and therefore the oil cannot disappear through the gap between the oil pump and the engine cover. The stud ends inside the oil filter compartment instead of at the oil pump output stud in the factory version.
The input whole of the oil filter compartment has to be enlarged to a diameter of 12.5mm to accommodate the new stud. The stud end carries a thread, too, that will not be on the full length of the stud inside the oil filter compartment, leaving a 2mm rest to the bottom of the oil filter compartment to act as a surface where an O-ring seal the feed-through of the stud through the bottom of the oil filter compartment. The O-ring is compressed a flat nut with a recess accommodating the O-ring.
To give the necessary room for the nut a spacer ring was machined and placed inside the oil filter compartment. An O-ring is placed below as already intended by the factory. At the top end of the spacer ring an O-ring of the same type is placed to seal against the oil filter element bottom end.
The rest of the oil filter setup is the same as realized by the factory, only the oil filter compartment cover has to be modified, so the spring will have enough space to become compressed sufficiently and the cover will fit on the oil filter compartment flange. Due to the spacer ring we will need about 8mm more space for the spring.
Needless to say that I choose Viton ® O-rings instead of the unknown and doubtful quality of the factory O-rings.
After assembling the described setup, a check of the oil amount at the rocker tips and rocker bearings was very satisfying. Now there is an impressing oil jet towards the valve shaft ends and the rocker tips even at idle and the ticking sound completely disappeared. The overall oil pressure and the oil flow is higher, a fact that also is a benefit for the hydraulic lifters, the crankshaft and transmission bearings.
The factory oil pump has the output O-ring fixed with superglue to the output stud. The O-ring material is not of a good quality and will not withstand the influence of the superglue. The superglue will penetrate the material and it will become brittle. As the superglue is not flexible, but adheres very good to the O-ring the O-ring will no longer be flexible but hard and when compressed will show cracks.
The oil pump is die-casted and the surface where the O-ring is placed is rough. On such a surface an O-ring cannot seal a joint.
The O-ring is placed between the oil pump output stud and the RH engine cover. Here, the surface is machined and plain. When placing the engine cover and tightening the screws the O-ring will be compressed and seal the joint between the oil pump stud and the oil filter compartment’s input whole – so far the way it was thought by the constructors.
This may be fine as long as the gap between the oil pump stud and the engine cover is correct, factory tolerances are small, the O-ring is of a good quality and the screw holding the engine cover will be tightened with the correct torque.
One important factor in the game are the gaskets between the oil pump body and the crank case as well as the gasket between the crank case and the engine cover as they determine the cap between the oil pump output stud and the plane where the O-ring has to seal the gap. The engine cover gasket as installed by the factory has a thickness of 0.4mm. The replacement gaskets our host offers have a thickness of 0.7mm, resulting in a gap that is 0.3mm larger. That makes the oil supply problem more serious as the O-ring will be more prone to leakage.
In view of this facts, the factory solution is very poor, as a leakage in these place will reduce the overall oil pressure and oil amount in the whole engine where the rocker bearings are the most sensitive ones. A reduced oil pressure and oil amount may lead to an insufficient lubrication of the rocker tips, too. The result will be a heavy wearing.
For a permanent fixing of the problem I recently ordered a new oil pump and converted it. The first step was milling off the top of the output stud with the O-ring recess and the rough surface to have a plain surface. Afterwards, the inner diameter of the stud was enlarged and a thread M12x1 mm added. Next, I machined a stud that carries an O-ring at the bottom end that is screwed-in in the oil pump. The O-ring seals the joint between the stud and the oil pump housing.
The stud has a flange on its opposite end, also carrying a (thicker) O-ring. The heights of the flange surface is the same as the O-ring accommodating recess on an factory oil pump. The lager cross-section of the O-ring will be more tolerant to differences in the thickness of the engine cover gasket. As the stud end is longer, it will lead through the O-ring and therefore the oil cannot disappear through the gap between the oil pump and the engine cover. The stud ends inside the oil filter compartment instead of at the oil pump output stud in the factory version.
The input whole of the oil filter compartment has to be enlarged to a diameter of 12.5mm to accommodate the new stud. The stud end carries a thread, too, that will not be on the full length of the stud inside the oil filter compartment, leaving a 2mm rest to the bottom of the oil filter compartment to act as a surface where an O-ring seal the feed-through of the stud through the bottom of the oil filter compartment. The O-ring is compressed a flat nut with a recess accommodating the O-ring.
To give the necessary room for the nut a spacer ring was machined and placed inside the oil filter compartment. An O-ring is placed below as already intended by the factory. At the top end of the spacer ring an O-ring of the same type is placed to seal against the oil filter element bottom end.
The rest of the oil filter setup is the same as realized by the factory, only the oil filter compartment cover has to be modified, so the spring will have enough space to become compressed sufficiently and the cover will fit on the oil filter compartment flange. Due to the spacer ring we will need about 8mm more space for the spring.
Needless to say that I choose Viton ® O-rings instead of the unknown and doubtful quality of the factory O-rings.
After assembling the described setup, a check of the oil amount at the rocker tips and rocker bearings was very satisfying. Now there is an impressing oil jet towards the valve shaft ends and the rocker tips even at idle and the ticking sound completely disappeared. The overall oil pressure and the oil flow is higher, a fact that also is a benefit for the hydraulic lifters, the crankshaft and transmission bearings.
