Oil Leak KZ900

If I have time tomorrow I plan to remove the valve cover and check the torque on the inside bolts

No need to remove the valve cover, all head bolts are located and accessible from the outside.

Thanks Scirocco, I'll go do it now then.

Pulled the tank and retorqued the head.  All the bolts were light... about 20 to 25 ft. lbs. I can see someone had this head off before I got it.  Possibly they just torqued it down without taking it through a couple heat cycles and rechecking. Will test ride tomorrow and see if I can get lucky with the Ultra Black.

If you check the book you will find there is a sequence to follow when torquing the head bolts.  I normally torque them up to about 20 ftlbs first, then go back through them in the proper sequence and bring them up to 25 ftlbs, which is the correct spec for a KZ900 or Z1 head.  (MK2 heads had a 28 ft lb spec.)

When you do a re-torque you must back the bolt off a half turn first, then tighten to the correct spec.  You do not need to nor want to over torque them.  If you break one you are in for a pile of work.

With respect to your head, you have a leaking head gasket that must be replaced.  I can see the gasket in your first photo.  Do not try to re-use it.  Buy new ones, preferably OEM.  They are expensive but they work.

Seeing how soon I will be building my engine and will need to re-torque. Is the proper procedure to loosen all head nuts 1/2 turn then re-torque to spec value in the correct sequence. 

That's how I do it.  If you don't slack them off a bit they may not be correctly torqued but may also be "stuck."

At this point you have nothing to lose but a little time in trying to re-torque the ENTIRE head.  You don't need to remove the cam cover to do this I don't believe.  Follow the bolt tightening sequence in the manual but be cautious going over torque values.  Even at suggested torque values bolts can sometimes break because they are no doubt old and you don't know what they have been through in their lifetime.  Here's the second rub, if you do end up taking the head off you risk disturbing the base gasket unless you are very careful.  Any upward force on the block can/will disturb that gasket so use due caution.  Also be careful separating the head from the block.  Watch your pry points and use appropriate tools for this job.  You don't want to break any cooling fins.  It's not the end of the world if you do break a fin, but it just looks tacky.  They can be repaired but it's a pain.  Good luck whatever route you take or are forced to go down.  If you think you may have disturbed the base gasket doing this project it is best to remove the block.  Yes dealing with getting the pistons back in is a bit of a hassle, but nothing to be afraid of.  The most difficult part of this entire job is cleaning the sealing surfaces to give yourself the best chance of leak free engine.

Rick H.

When retorquing a head I back off the nuts just enough to get them moving then Immediately tighten them to the proper torque number.  The nuts can get quite sticky so some antiseize is useful on the stud threads.  And speaking of sticky, I've got a couple of really nice and highly accurate dial type Precision Instruments torque wrenches (with Snap-On branding.)  One time I was torquing some head nuts which were sticking and when turning the nuts there was a snap/crack sound which shocked the torque wrench and broke an internal part.  It cost me close to $100 to fix with two way shipping and the repair/calibration.  Now I use a $25 beam type torque wrench on used motorcycle heads because they can take far more abuse.  Beam type torque wrenches never go out of calibration either.  

Nessim's advice above is best practice IMHO.

No one has mentioned the two 10mm. head bolts just outside of the #'s 1 and 4 spark plugs.  70 in./lbs. if memory serves.

Good Ridin'
slmjim& Z1BEBE

@Nessism, I understand from your last post, on backing bolts and immediately torquing them, that you mean going through the bolts one by one and following the order proposed on the book with the book values. Right? 

I also understand that procedure of redoing it after a couple of heat/cool processes, does not imply backing bolts, but just rechecking torque.

Right? 

Thank you so much for the info!