Oil for a Rebuilt Engine

[johnners987]

Been trawling through some of the oil topics and, from what I can gather, most of you recommend 10W40 semi-synthetic. Having noted that I have a question in relation to the initial oil fill after an engine rebuild that hopefully someone can help with.
It has been suggested to me that mineral oil is best post rebuild - as it isn't as protective as synthetic and is therefore better for bedding in rings/ bores etc. - before switching to semi-synthetic after 500/600 miles for 'normal' protection. Anybody got experience or any views on this?
Also, having just dropped the filter housing to fit a new filter, I note the new filter comes with two o-rings only one of which appears compatible with the removed filter housing (the smaller of the two housing o-rings). Am I missing something? I realize the filter is not solely TRX applicable but cannot understand why it would come with only one of the two requisite o-rings...... although, again, I note that replacing o-rings is only considered necessary if they are considered damaged. To say the least I am a little confused!
All/ any comments, as always, greatly appreciated.

[dandywarhol]

I would run it in with mineral for 1000 miles and change (with filter) for semi-synth.

It's my belief that these motors suffer from bore glazing and oil consumption from too gentle running in and synth

[johnners987]

I would run it in with mineral for 1000 miles and change (with filter) for semi-synth.

It's my belief that these motors suffer from bore glazing and oil consumption from too gentle running in and synth

Thanks for the quick response. Would you advocate 10W30 or 10W40? I guess, given our climate, I'm surprised most go for 10W40 but I realise it isn't quite that straightforward.

Any comment about the o-rings?

Cheers

[misterdimwiddy]

Have always used 10W40 (Castrol Power 1 semi synth) to try to keep the oil pressure up a bit!!

[dandywarhol]

That's good when the engine has been run in after the rebuild. Synthetic is too "slippery" to allow proper bedding in of the rings/bores

[misterdimwiddy]

Oh crap. Hope that's not the cause of my smoke!

[johnners987]

That's good when the engine has been run in after the rebuild. Synthetic is too "slippery" to allow proper bedding in of the rings/bores

Thanks again. This was the initial advice I had. Can you educate me on whether the mineral oil needs to be flushed prior to replacing with semi-synth? I nipped in to my local bike shop to see if they had any mineral oil (and they didn't!) but they quizzed me on the 'why' and asked me(!) if I would need to flush it after draining before refilling with synth. What the hell do I know!
As for the o-rings, neither of them supplied with the Yamaha genuine filter I have seem to be required for the TRX (they are both incompatible sizes) so I assume they are for another application.
Onward and upward!

[dandywarhol]

If you were going fully synth (which I can se no point in going - it can cause wet clutch problems) then a flush would be recommended. Just going to semi synth shouldn't need a flush out as it is partly mineral based anyway.

Just make sure you drain off from both oil drain holes and when you restart the engine check the oil is getting to the head by loosening off the 10 hex bolt on the left side of the head to see it coming through

[johnners987]

Cheers mate. Should get the tank back soon so I'll be in a position to the undertake that first (nervous) start up.

[Mincehead]

I would run it in with mineral for 1000 miles and change (with filter) for semi-synth.

It's my belief that these motors suffer from bore glazing and oil consumption from too gentle running in and synth

Yep 100% with you on this.