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1978 CB400T head bolt tightening sequence?

gearsoup

gearsoup

Veteran Member
Joined
May 1, 2023
Total Posts
148
Total likes
10
Location
Maine
I'm getting ready to get my motor back together, and I've run into a discrepancy in the literature. The Clymer manual says to start with the outside bolts, the FSM says to start with the in-board fasteners. Now, in the multiple Subaru (car) motors I've done head jobs on, it's been the in-board that gets addressed first, so my natural inclination was to go with those anyways...

Clymer.jpg FSM.png

The FSM says "Tighten in 2-3 steps". I interpret this to mean: finger snug in proper order, little bit tighter in same order, little bit more, than a final tight to torque. Correct?
Other question is; should I apply any lubrication or rust preventative to the threads? In past engine builds (again, Subaru), I've dipped the threads in engine oil. Good/bad idea?
 
I'd wait to hear from Jim (LDR) about this since these engines are his specialty, but I'd agree that something on the threads is a good idea just based on the many times I've read how difficult they can be to remove without issues later. I'd certainly trust the FSM on the tightening sequence.
 
Considering 4 of them have oil flowing right by them, I'd be apprehensive about using something that would contaminate the oil supply (tin-man anti-seize for example)
 
Jim's been busy at home lately but I'm sure he'll check in sometimes this afternoon, he's on the west coast so he's in Pacific time
 
Use the FSM method, Clymer is dead wrong. Head bolts are always done from the center out regardless of engine.
I guess I do 3 steps since I run all the bolts down with a ratchet first then @1/2 torque and then full torque. Bolts are intended to go in dry but nothing says you can't coat the threads BUT if you do then use the low end torque spec.
 
LDR, thanks for the confirmation.
One other area where Clymer and the FSM differ is in regards to the camshaft holders. In the FSM, it has this bit of info: "Apply liquid sealant to the head contacting faces of the camshaft holders". The Clymer has no such note.
In fact, when I took the camshaft holders out, there was no gasket material of any sort between them and the mounting points on the head. To what is the FSM referring to; PermaTex silicone gasket maker (or similar)?
 
gearsoup said:
LDR, thanks for the confirmation.
One other area where Clymer and the FSM differ is in regards to the camshaft holders. In the FSM, it has this bit of info: "Apply liquid sealant to the head contacting faces of the camshaft holders". The Clymer has no such note.
In fact, when I took the camshaft holders out, there was no gasket material of any sort between them and the mounting points on the head. To what is the FSM referring to; PermaTex silicone gasket maker (or similar)?
Click to expand...
I use Honda Bond HT there although something like Gasga Cinch will work. IN NO case ever use silicone gasket maker ever. Honda Bond is the only sealer to use and only a very thin smear is needed any where it's used.
Clymer manuals are good for absorbing spilled oil, propping things up, kitty litter box material, etc.
 
LongDistanceRider said:
I use Honda Bond HT there although something like Gasga Cinch will work. IN NO case ever use silicone gasket maker ever. Honda Bond is the only sealer to use and only a very thin smear is needed any where it's used.
Clymer manuals are good for absorbing spilled oil, propping things up, kitty litter box material, etc.
Click to expand...


Isn't HondaBond HT a silicone gasket product though? LINK to Amazon
 
LongDistanceRider said:
Yes, it is silicone based. However it's very unlike any of the silicone gasket maker products in that it is formulated specifically to seal metal to metal contact w/o hardening or breaking free to clog oil passages. It's made by ThreeBond
Click to expand...

AND, if it wasn't appropriate for use in Honda crankcase and other gasket surface situations, Honda wouldn't have a version with their name on it.
 
Clarification on the valve cover bolts: finger tight or torque to spec?
2023-06-17_08h46_41.png
 
Since this is one of a very few areas with a part that this bike shares with another bike I've owned (CBX has the same valve cover bolts, just lots more of them), be very cautious when torquing to spec. And BTW, nothing on our bikes should ever be just finger-tight, they vibe and finger-tight stuff will eventually come loose and fall off.

Since those are shouldered bolts, they only be tightened up until the shoulder hits the aluminum of the head and the bolt is just tight. Despite them having a torque value, it would still be easy to snap one off using something the length of a torque wrench. If you have a good "feel" for tightening small bolts, just use a wrench or 10mm socket on a 1/4" drive ratchet (shorter length handle) and make them tight but no more, like you would for a drain plug. The whole purpose of the shoulder on the bolt is to limit how tight you tighten them so you don't crush the rubber seal on the bolt too much and distort it so IT leaks, but the rubber seal (when new) exerts pressure on the cover to help the cover gasket seal while sealing the large hole for the bolt with rubber cap seal.
 
Ah, didn't realize they were intended to act as shoulder bolts. Makes sense. And yep, new rubbers :)
 
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