Topic: cb400f engine case bolt torque specs.

[andrsn]

Anyone know what all the 10mm engine head bolts are supposed to be torqued to? I've got some oil leaking from the top of the engine and want to make sure everything is torqued to spec before I try other things. Can't find the info in my manual.

[magconpres]

Cylinder Head 8mm, 1.25 pitch:  14.5 Ft-Lbs (200 kg-cm). oil threads first.

Note that while the bolt heads are 10mm, the thread diameter is only 8mm.

[camelman]

Let's make sure you are talking about the cylinder head bolts.  There are about 18 bolts for the valve cover that are torqued roughly hand tight.

The cylinder head bolt torques seem to range from 14-16 ft-lb.  I've seen that range given a few times, so I go by the upper end of it usually.  If you have done any performance work (466 kit, higher compression pistons, etc.) then you can even go up from there.  Kaz Yoshimura recommended 18 ft-lbs for his race bikes without mention of replacing the stock studs.  FYI, I have a 466 kitted engine with bored out carbs that I have torqued to 16 ft-lbs and do not have any leaks or issues (that is a very fast engine too!).

Camelman

[andrsn]

Yeah, there are maybe 18 (not in front of me at the moment) They are the bolts you would remove after taking the breather cover off if you were about to take your engine apart (you can see them when the engine is assembled). Are these the valve cover bolts? I don't know the terminology.

thanks

Let's make sure you are talking about the cylinder head bolts.  There are about 18 bolts for the valve cover that are torqued roughly hand tight.

The cylinder head bolt torques seem to range from 14-16 ft-lb.  I've seen that range given a few times, so I go by the upper end of it usually.  If you have done any performance work (466 kit, higher compression pistons, etc.) then you can even go up from there.  Kaz Yoshimura recommended 18 ft-lbs for his race bikes without mention of replacing the stock studs.  FYI, I have a 466 kitted engine with bored out carbs that I have torqued to 16 ft-lbs and do not have any leaks or issues (that is a very fast engine too!).

Camelman

[camelman]

I was guessing at 18 too, but we are talking about the same bolts. Just take them hand tight. They strip out easily, so don't try to crank them. I usually tighten in a few rounds to make sure I don't overload any threads or bolts.
I've seen people call for 3 ft-lbs on them before, but definitely less than the manual states.

Can anyone else recommend a bolt torque?  I just do it by feel now.

Camelman

[andrsn]

sounds good. I'll torque them evenly, a previous owner stripped two of the outer bolts (where it was leaking oil). I tapped them to 7x1mm bolts and hope that will work.

I was guessing at 18 too, but we are talking about the same bolts. Just take them hand tight. They strip out easily, so don't try to crank them. I usually tighten in a few rounds to make sure I don't overload any threads or bolts.
I've seen people call for 3 ft-lbs on them before, but definitely less than the manual states.

Can anyone else recommend a bolt torque?  I just do it by feel now.

Camelman