xr600r - what oil

[metisse]

I just pulled the head cover on my '91 to investigate tappet noise and find the exhaust rocker arms shot. It has maybe 30k miles on it and is treated to regular oil and filter changes - Is this a sign of modern oils not having the same amount of high pressure lubricants in them? - less phosphorous and zinc - apparently SL and SM oils have way less high ressure additives, to cut pollution and because most engines have roller followers now?

[Beyond The Pale]

The modern oils have less zinc and phosphorus so they are nicer to the catalytic converter. I've been using older SL Rotella T 15W-40 for years and I have no issues like this, yet. I went out and got 2 cases of the old formulation. The new stuff is SM and has less zinc.

One thing is for sure, any reduction or blocking of the oil supply kills these motors. The head always suffers first. Just a little twist in the oil line from the frame tube to the pump is all it takes to starve the engine of oil. There are may possibilities for a flow issue. When you rebuild, verify that oil does get to the head or it may fry again right away. This has happened to several in this forum.

There are a few mods that can be done to help the oil supply to the head. Things like drilling out some of the passageways on the oil tube. You can also replace the oil tube with a larger hose. Do some searches on this forum and you should find them.

[metisse]

Thanks cleonard - I will be checking the whole oil system - all the external lines look ok from the outside - the head was awash in oil on strip down, but that doesn't really tell if there is adequate flow - the first thing a respected local motor guy said is 'check the oil pump'!

It has alerted me to the question mark around modern car oils having less high pressure additives so I will be looking for a "comfort" oil.

[martinfan30]

i would replace the oil pump any time i would rebuild one of these!

[metisse]

Thanks guys - The manual gives specs for the oil pump clearances so we will check it and all the passages carefully on the way back to life!

[HeadTrauma]

The unfortunate news is that the new diesel engine oil classification finally changed to mimic the automotive oils. The bittersweet plus side is that motorcycle and automotive racing oils seem to have retained at least the zinc. The bitter part is that even straight petroleum bike oil cost the same or more than automotive synthetic. The automotive oils may or may not have high levels of moly, so be aware of that too.