Re-torquing Cylinder Head Nuts on a KZ750 Engine

I have a KZ750 engine whose top end was rebuilt a few years ago with a big-bore kit.

I need to investigate further, but it appears there may be a small oil leak from the head gasket around the left-side oil passage.

My question is: Is there any concern about re-torquing the cylinder head nuts?

My plan is to loosen each nut slightly and then re-torque it, one at a time, following the tightening sequence and torque specification in the service manual.

Bummer about the leak.  The 650/750 engines commonly leak at the head gasket, to the point of almost being a "normal" condition.

Torquing the head nuts should be part of normal maintenance.  It's specifically called out in the service manual on Suzuki GS bikes, but Kawasaki just has a generic reference stating to check bolt tightness every 10k kilometers.  

When torquing head nuts, back off the nut just enough to get it moving, then quickly reverse direction and bring the nut up to proper tightness.  Be careful when breaking loose the nut because it may stick and emit a snap/crack sound.  No big deal, but the sticking can shock some torque wrenches and damage them.  I learned this last part the hard way.  

I have used the bike for around 5–6 seasons (although it hasn’t been ridden much each season), and I haven’t had any oil leaks since the engine was rebuilt.

If it turns out to be a leak from the head gasket around the oil passage, is it common for this to happen because of the relatively high oil pressure in that area?

Thank you for your assistance.

If you already have a leak re torquing the nuts most likely won't help but its worth a shot.

I have a 750 that recently developed a base gasket leak after running for about 800KM after a top end rebuild. The leak started at about 600KM. Admittedly I had flogged the engine on several occasions to about 8K.

I am religious about cylinder head nut torque and it still leaked. I kept upping the torque in 2 pound increments to about 34 lbs and it never stopped leaking, once they start the only cure is a rebuild.

I only re-torqued the head once or twice after a few heat cycles during the break-in period for the new pistons and rings.

I’ll re-torque it and see if that helps, but first I need to find my notes to see what torque value I used on the head nuts during assembly.

Should I use the same torque specification, or is it recommended to increase it slightly?

Use manufacturer spec, any more risk's pulling the studs out of the crankcase like a "cork from a wine bottle" (ask me how I know !!!)

Thanks, but I assume it’s important not to end up with less clamping force than I have now.

I’m fairly sure I used the torque specification from the service manual, but I’ll do some digging to confirm.

Is the order in which I check and re-torque the head nuts important, or can I loosen and re-torque them one at a time in any order?

The order doesn't matter since you are doing one at a time.  And again, loosen just enough to get the fastener moving, then tighten.  

Spec is 4.0 kg-m / 29 ft-lbs