head torque 1976 KZ750B1

I NEED TO KNOW HEAD TORQUE ON MY 1976 KZ750B1 TWIN I JUST ORDERED A MANUAL BUT IT WONT SHIP UNTIL 7/26/08. I WANT TO RIDE.

MARK LIMING wrote:

I NEED TO KNOW HEAD TORQUE ON MY 1976 KZ750B1 TWIN I JUST ORDERED A MANUAL BUT IT WONT SHIP UNTIL 7/26/08. I WANT TO RIDE.

I have a KZ750 B4 and the torque spec for the head bolts is about 27 - 33 foot-lbs, which is about 320 - 400 inch-pounds. 30 foot-pounds is nominal, that's 360 inch-pounds.

I recommend a lower range torque wrench like 500 or 600 inch pounds maximum. You won't get good resolution on the big wrenches that go up to hundreds of foot-pounds.

If you are also working on the camshafts, be careful torquing the bolts that hold the camshaft caps. The manual spec is about 100 inch-pounds, DO NOT EXCEED IT as they seem to strip very easily. Some say that value is too high, but I have always used it (you have to do it accurately).

The valve cover bolts also spec at 100 inch-pounds, but that is too much for it IMHO (about 60 is plenty).

good luck on the rebuild

Hi!

Old thread I know. Torque specs on different head related nuts and bolts? I find the torque specs given in the service manual too high?
The camshaft cap bolts (see attached image/spec from the service manual)?
The cylinder head nuts (see attached image/spec from the service manual)?

Any thoughts/information/experience about the above?

Ride safe!

Fredrik
 

Mk 1 human hand torque. If it feels to tight for forty year old steel into alloy its too late you've already stripped the thread. 

The torques are designed to provide the correct clamping force, so that the fastener doesn't begin to slip while in operation.  Threads should be cleaned and chased beforehand.  Threads in aluminum can be easily damaged, so I approach the torque spec carefully and try not to put any stress on them.  I bring cam cap bolts up to around 75 in lbs and had no problems.  I bring head bolts up to specified torque range.

The most important thing is to use a torque wrench.  Guessing is best left to experts.

wrote:

The torques are designed to provide the correct clamping force, so that the fastener doesn't begin to slip while in operation.  Threads should be cleaned and chased beforehand.  Threads in aluminum can be easily damaged, so I approach the torque spec carefully and try not to put any stress on them.  I bring cam cap bolts up to around 75 in lbs and had no problems.  I bring head bolts up to specified torque range.

The most important thing is to use a torque wrench.  Guessing is best left to experts.

Important detail, thread "chasers" are the proper tool, not regular taps that remove metal from the threads.  The fasteners should be installed dry too, unless told otherwise in the manual.  

When torquing the head, it's important to come back after a few heat cycles and retorque.  Do this until subsequent checks show the torque is not falling off any longer.  If using OEM gaskets, that should happen pretty fast.  With aftermarket gaskets, all bets are off.

 

wrote:

The torques are designed to provide the correct clamping force, so that the fastener doesn't begin to slip while in operation.  Threads should be cleaned and chased beforehand.  Threads in aluminum can be easily damaged, so I approach the torque spec carefully and try not to put any stress on them.  I bring cam cap bolts up to around 75 in lbs and had no problems.  I bring head bolts up to specified torque range.

The most important thing is to use a torque wrench.  Guessing is best left to experts.

Thanks!

75 in Ibs sounds ok for 6mm bolts but thats quite far from the service manual recommended 95-113 in ibs. Its only 6mm bolts.
I use a torque wrench for this kind of work.

Fredrik

I have torqued several of these heads/cam cap bolts to the torque numbers in the manual. no problems yet. On two 750 twin engines i replaced the stock cylinder studs with APE heavy duty studs and torqued the head studs to 37 ft lbs.


FYI since you will be needing a new head gasket and these bikes are notorious for head gasket leaks -

A little gasket history :
11004-071 => 11004-078 => 11004-1055 => 11004-1267
11004-071, recall campaign in June 1976- BAD
11004-078, the red one with black middle section -BAD
11004-1055, light brown, comes with the first LTD model - GOOD
11004-1267, the green and the best for the last LTD model - BEST

www.z750twin.de/zylinderkopfdichtung.htm

 

This is how I did it. KZ750B -1976.
Head nuts torqued to spec as the service manual (27 ft ibs / 37 Nm).
Torqued the cam cap bolts to app. 8.5 Nm / 75 Ib in (at first I followed the service manual but broke two bolts. I am NOT a professional wrencher.) 

Ride safe

Fredrik