Topic: 1978 CB 550 K4 head torquing sequence

[mbryan]

I have looked at the manual, did lots of reading here, and looked at videos and have a few questions surrounding the torquing procedure for the head on this motor. 

The manual says go to 16.6 ftlbs in a certain pattern.....which includes the two small 10mm bolts on the front and back of the engin .  However,  I have read here to not torque down those small bolts to the specified specs per the manual.......so what is it?  I also saw to put hondabond around those bolts.....how do you do that as the gasket surrounds the bolts.  Also,  I have seen it written here to torque everything down then let it sit for 24 hours.  After this period of time back off the bolts one full round in sequence and then retorque back to factory spec.....is this best practice?  Lastly I have seen the same after the engine has had a heat cycle.....what exactly is a heat cycle.....run at normal speeds for x miles or time?  If the heat cycle idea is best practice do you loosen all bolts again and retorque like above or just check torque.....if you do, do you need another set of rubber pucks to ensure no leaks afterwards?

Just looking for clarity and best practices to ensure a leak free bike.

Thanks in advance for any info!

[DaveBarbier]

No need for Hondabond around those bolts.
Torque the head nuts in sequence then wait 24 hours for stud stretching and gasket compressing and then loosen in sequence and retorque. Some don’t do this and it’s fine but some don’t and then had leaks and then they retorque and everything is fine. After the 24 hour retorque install and tighten those two small bolts. Just use a 1/4” ratchet and choke up on it so you don’t put too much force into it. Just nice and snug is all they should get. Avoid putting a torque wrench on these or any bolts/screws this size. I have cracked head covers this way.

Heat cycle just implies running the motor to full operating temp. It might aid in bedding the head gasket. Don’t think it’s necessary for these bikes. If you’re building a formula 1 engine then probably.

Edit: Some like to creep up on the full torque spec for the head nuts. Like first do a round at like 10ft/lbs and then sequence at full torque. Can’t hurt.

Edit 2: The 650 manual says to lube the head threads with grease. I was looking and couldn’t find it in the 550 manual. I would put some oil on the threads to get proper torque.

[mbryan]

Ok....can I use never seize on the head bolts instead of oil?

[DaveBarbier]

Ok....can I use never seize on the head bolts instead of oil?

That’s not really a lubricant but if it’s there you could add a bit of oil too. Little dab’ll do ya.

[jonda500]

You will find many different opinions about this. I prefer to retorque the head with the engine cold, without loosening them. One by one in the tightening sequence but first to break them free of any stiction I crack them loose in a clockwise direction but only barely turning them and then torque to spec (I have to go past the specified torque to crack them then release the hand pressure and re-apply pressure to get to the correct torque value. Usually most but not all of them turn a bit before reaching the setting).
If you are loosening them I hope you do it in the reverse of the tightening sequence!
John
p.s. I don't do the after 24 hours re-torque as I am always impatient to start the engine/ride the bike!

[RAFster122s]

If you use anti-seize or oil on the threads you need to lower your torque numbers unless the manual tells you to torque to that level AND to oil the bolts. Otherwise, your torque numbers are going to be too high.

[DaveBarbier]

You will find many different opinions about this. I prefer to retorque the head with the engine cold, without loosening them. One by one in the tightening sequence but first to break them free of any stiction I crack them loose in a clockwise direction but only barely turning them and then torque to spec (I have to go past the specified torque to crack them then release the hand pressure and re-apply pressure to get to the correct torque value. Usually most but not all of them turn a bit before reaching the setting).
If you are loosening them I hope you do it in the reverse of the tightening sequence!
John
p.s. I don't do the after 24 hours re-torque as I am always impatient to start the engine/ride the bike!

Yeah, I do the same. You only need to crack them loose. Honestly, cracking them loose a quarter turn completely loosens the nut anyway. It’s NOT rocket science. You just want to loosen the nuts and retorque.

[DaveBarbier]

If you use anti-seize or oil on the threads you need to lower your torque numbers unless the manual tells you to torque to that level AND to oil the bolts. Otherwise, your torque numbers are going to be too high.

Hey David, I just checked and in the back of my Clymer manual it says to oil the threads. Wonder if the Honda FSM for the 500-550 says the same. In my Honda FSM for the 650 it says it in the back of the book too, not in the “installing the head” section for some reason. 

[mbryan]

Thanks for the discussion guys.....trying to start out with a leak free head

[mbryan]

Hey all......revisiting this again.  I know I am probably making this too hard but I have a question on what yall are suggesting.  I have toured everything down and will let it sit till tomorrow evening. Sooooo.....do I start from the reverse order of the torque sequence and loosen all of them slightly.  Then retorque as per the book in sequence? ........or do I do this one at a time in that I start from the outside and go backwards in the sequence and loosen one at a time and retorque that one then go to the next?

[DaveBarbier]

Loosen all in reverse order and then tighten in correct order.

[mbryan]

Got it.....thanks