Sorry. It's an oil question.

[hank]

A friend of mine who has been riding beemers for 30 years just got his R1100RS back from the dealers after an engine rebuild.
His bike had done 39,000 miles is well maintained, doesn't get thrashed or abused, but still managed to wreck the bearings.

The mechanic offered no explanation as to why this could have happened, although he did mention that there was some grit in the petrol tank. Work carried out included new big end bearings, small end bearings and new con rods.

Now for the dreaded oil questions.

The dealer told him that if he has used semi synthetic oil in the engine then he must never change it back to mineral oil. Is there any truth in this?

Also, could a change from semi synthetic to mineral oil cause the bearings to fail?

 

[Kenny]

As long as he changes the oil filter when he changes the oil...then all will be OK

 

[D6]

why would it be a problem changing back??semi will mix with non semi

 

[Steptoe]

The mechanic offered no explanation as to why this could have happened, although he did mention that there was some grit in the petrol tank. Work carried out included new big end bearings, small end bearings and new con rods.

Now for the dreaded oil questions.

The dealer told him that if he has used semi synthetic oil in the engine then he must never change it back to mineral oil. Is there any truth in this?

Also, could a change from semi synthetic to mineral oil cause the bearings to fail?

What has grit in the petrol tank got to do with needing an engine rebuild. About as relevant as grit on the brake pads.

Changing the oil from one spec to another makes diddly squat difference. BMW changed the spec a while back from fully synth back to mineral while running the engine in , go figure.

 

[Colban]

I've gone from semi-synth to mineral;no problems.Which dealer came up with that gem?.
39k is a very low mileage for a boxer to need a rebuild.Was the oil pump changed as well?.
Additional thought..has he got a locking oil filler cap or the original plastic thing?.
Can be far too easy to add sand or similar to the oil.

 

[motobiker]

The old fuel tank on my bike shed its inner liner.. unknown to me at the time, was only discovered when I had the fuel filter changed over.

The stuff.. brown paint (lead oxide I guess) was coming out in sheets... it was amazing to see how much there was. It had absolutely no ill effect on the running of the bike however.

why should it? the bike has a fuel filter.

 

[King Rat]

How can a machine that requires a full engine rebuild at 40,000 miles be described as "always well maintained"?

 

[motobiker]

I've gone from semi-synth to mineral;no problems.Which dealer came up with that gem?.
39k is a very low mileage for a boxer to need a rebuild.Was the oil pump changed as well?.
Additional thought..has he got a locking oil filler cap or the original plastic thing?.
Can be far too easy to add sand or similar to the oil.

I've often wondered about the paranoia behind buying the locking oil filler cap.. yes I guess deliberate sabotage is something that can happen.. but how likely is it? not very.

How many sabotaged bikes have you seen over the years Steptoe?

My guess is that there was some sort of catastrophic failure in the engine.. a bearing 'breaks' and causes this damage.. we all know that bearings can and do fail horribly.. in the final drive for instance. No real reason for this.. it 'just happens' - sods law.. we accept it, replace the bearing and the thing can last the life of the bike.. or indeed fail again a month later.

Why not in the engine? sods law can be a right pain.

As for the rest. the dealers ideas.. seems to me that a lot of people.. some on this site have some very strange ideas about these bikes... the same can go for dealerships I suppose. Oil questions being the biggest source of strange ideas there is. But is it not in the dealers best interests from a profit point of view to keep this owner buying a higher priced oil? profiteering... surely not.

but then.. this is all second hand. I wasn't there and don't know exactly what was said.. maybe the op's friend misheard or misunderstood.. could that be a possibility? I guess the final bill for this was a horrible shock.. and shock can have some mighty strange effects on your thinking processes.

 

[davegs]

Re build

I would think that this "experienced owner" should check his oil level more than once a year.