lube for cylinder head bolts


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ntintruder
Posts: 39
Joined: Tue Jun 28, 2011 9:07 pm
Location: Willoughby,OH
Motorcycle: 1976 GL1000
1972 CB750K2
1977 CB750f

lube for cylinder head bolts

Postby ntintruder » Sat Jan 31, 2015 12:07 pm



Can anyone recommend a molybdenum disulfide based grease for cylinder head bolts? My shop manual and Randakk both say to use it when installing the bolts but everything I've seen at O'rielly's, Auto Zone etc., goes by a brand name and I want to make sure I'm getting the right stuff.



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HawkeyeGL1200
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Location: Courtland, Va.
Motorcycle: 1984 GL1200 Interstate
1981 GL1100 Interstate

Re: lube for cylinder head bolts

Postby HawkeyeGL1200 » Sat Jan 31, 2015 9:03 pm

Honda moly60, or whatever the exact name is... Having a senior moment here... Is 60% molybdenum disulfide and it is very well suited for the application of lubricating threatened
fasteners.
I am wrong as often as I am right concerning what is wrong with someone else' motorcycle without having seen the machine in person. Guessing with limited information, as to the source of the trouble, is sketchy at best.

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Aussie81Interstate
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Motorcycle: 1982 CX500 Turbo (restoration project)
1981 GL1100 Interstate (sold)
1988 GL1500

Re: lube for cylinder head bolts

Postby Aussie81Interstate » Sat Jan 31, 2015 9:51 pm

Shoot me if I'm not in 100% agreeance here.

I believe there should be no moly on the head bolts - the idea is to torque them to specifications - any grease affects their ability to lock the thread in place in the head. The bolts are supposed to be done up to the required tension - not with any grease to possibly overtighten or over torque the bolts because of the slippery grease on the threads..
just my 2 cents worth here.. :)

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aussiegold
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Motorcycle: 1975 Goldwing (No 8 to come to Oz )
1976 LTD cleverly diguised as an 81 interstate
1976 LTD.. a feller with 2 LTD's can't be all bad.....

Re: lube for cylinder head bolts

Postby aussiegold » Sun Feb 01, 2015 1:32 am

my manual also says to use grease on the threads and also under the heads of the bolts. any grease with moly listed in its make up will do . grease and other lubes have come a long way since the 70's. any good brand should be ok.
i reckon its wise to just smear a LITTLE on, just a tiny wipe. i also give the bolt washers a bit of a going over with wet n dry, just to take any burrs off.
having said that, i am also of the opinion that greasing the bolts might give a false tension reading, but there you go..... it's in the Honda manual.
a quick survey of a couple of friends comes up with different opinions. two use grease, three use engine oil and one swears that dry is the way. seems to be a bit like head gaskets , some say put em on dry , yet the manual calls for a sealant. i have done them both ways , with success.

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HawkeyeGL1200
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Motorcycle: 1984 GL1200 Interstate
1981 GL1100 Interstate

Re: lube for cylinder head bolts

Postby HawkeyeGL1200 » Sun Feb 01, 2015 8:04 am

Generally, fastener torque values are expressed in terms that are either"dry" or"lubricated. The specification takes the additional tension applied to lubricated bolting if some kind of anti-seize is specified. Applying thread lubricant to the bearing surface of the bolt head is more beneficial than applying lubricant to the threaded section of the bolt.
I am wrong as often as I am right concerning what is wrong with someone else' motorcycle without having seen the machine in person. Guessing with limited information, as to the source of the trouble, is sketchy at best.

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WingAdmin
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Re: lube for cylinder head bolts

Postby WingAdmin » Mon Feb 02, 2015 10:41 am

HawkeyeGL1200 wrote:Generally, fastener torque values are expressed in terms that are either"dry" or"lubricated. The specification takes the additional tension applied to lubricated bolting if some kind of anti-seize is specified. Applying thread lubricant to the bearing surface of the bolt head is more beneficial than applying lubricant to the threaded section of the bolt.


Correct. When you're torquing a bolt, there are two things resisting it turning:

- Stretching of the bolt itself. This is determined by the type of steel used to make the bolt, as well as how many times the bolt has been torqued in the past. This is primarily what keeps bolts "tight."

- Friction of the threads against one another, and of the head of the bolt against whatever it is seated against. This varies depending on whether or not the threads are contaminated with oil, water or anything else, and if the bolt head is wet, dry, hot, etc.

When the amount of torque to be applied is critical (i.e. in a head, where you want it perfectly balanced) the manufacturer can specify that the bolt threads and heads be lubricated, as is the case here. By doing so, they remove the "unknown" of the bolt friction, and are left only with the stretching of the bolt determining the amount of pressure applied, which they are able to control.

ntintruder
Posts: 39
Joined: Tue Jun 28, 2011 9:07 pm
Location: Willoughby,OH
Motorcycle: 1976 GL1000
1972 CB750K2
1977 CB750f

Re: lube for cylinder head bolts

Postby ntintruder » Tue Feb 03, 2015 2:07 pm

Thanks to everyone who responded to my question about lube for cylinder head bolts, especially WingAdmin who provided the best explanation I've seen for the need to lube the bolts. We both live in the same Ohio area so maybe we'll meet up one of these days.




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