Changed oil (Motul 5100 semi-synth) on my TT600R today and mounted a KN oil filter.

O-ring on the oil filter cover was intact so I reused it. Went on a 30 min drive and when I got back i noticed that oil is seeping from the bottom of the oil filter cover, maybe the bottom screw hole.

The leak is VERY VERY minor, its not like its dripping or making a mess.

The thing is, that its only leaking when the engine/oil is hot. Nothing is visible when parked (even for hours - maybe because of the angle of the bike on side stand?) or starting up. I went for another 20 min ride and for the first 15 mins, I couldn't see any oil. It seems that it only seeps when the oil hits around 80+ degrees.

Don't know if it matters, but I used Yamalube (changed at dealer) and an OEM Yamaha filter before that.

Any ideas of the cause?

EDIT:
What I meant was that I have heard about some bikes starting "sweating" oil when changed to a different kind of brand most notably full-synth. If its "just" the o-ring I can't understand why its only when the bike is hot.

its not the oil that make this problem, i have only used motul for last 6years and never any problems. Change the O ring and you will be fine, did you use torque on the screws? Reason why its not leaking when on stand is because there is no oil at this side.

That, and oil is thinner when warm.

Thesse bolts require very litlle torque. Just a bit past finger tight, you only need the torque to compress the oring.

Get a new o-ring kit, so you also change the small one.

The main reason for not over tightening the bolts as they are easy to strip, especially the bottom one. There is not enough threads to hold much torque and most wind up getting stripped.

Two ways to fix the stripped threads. Carefully install a thread kit, one brand is heli coil. These take a special sized drill bit and carefully drill then using the provided tool you turn in the threads from the outside and break off the little tang being careful to retrieve it. It might be better to remove the whole clutch cover so you can drill and insert easily and remove the little tang and not lose it.

Another way is to use a slightly larger bolt. Standard thread is 6mm but the standard bolt is a special. There is not much room for error and you get 1 shot at it. Drill and tap to 7mm if I remember correctly. Make sure you get a bolt long enough, perhaps slightly longer than the original one.

The purpose for this bottom bolt and o ring is it will drain the oil filter cavity when it is not running and make less of a mess when you change out the filter.

Using a larger bolt may negate this feature. I have done this to my 84 XT and also filled the drain hole from the filter cavity with JB Weld so oil cannot get around this bolt. Works perfectly. You do have to enlarge the cover hole to accommodate the larger bolt. I put a flat washer under the bolt head unless you can find a flange bolt long enough.

I have had slight oil leaks from this cover even with a new o ring so I use a little yamabond or similar to get it a good seal that does not get hard and easy to clean up. I do the same thing on the gas tank fuel valve, stops any gas leakage.

Steve

You might try and find a slightly larger o ring. One that has a larger cross section so it will extend out of the groove slightly more and will squeeze tighter.

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

Thanks for the tips!