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Author Topic: 1981 CB650 engine rebuild question  (Read 1645 times)

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Offline Calaya

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1981 CB650 engine rebuild question
« on: March 13, 2017, 08:12:58 AM »
Hi, everyone.  With the aid of my father-in-law (who is a truck mechanic) we tore down the engine, however; several bolts were seized but we got them loose.  In making plans to reassemble it in the near future, however, we noticed that the manual doesn't indicate whether to use oil, grease, or anti-seize when reinstalling the (12, long) cylinder head bolts.  Does anyone have any experience or advice related to this?  If the manual doesn't specify (with this and other instructions) do we just simply reinstall?  Thanks for your help.
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Offline SOHC4 Cafe Racer Fan

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Re: 1981 CB650 engine rebuild question
« Reply #1 on: March 13, 2017, 09:13:29 AM »
Quote from: calj737 on March 13, 2017, 09:01:17 AM
A light oil wipe is fine. Step them into the block to their final torque (8# I think). The cylinder nuts get stepped to about 16-18# in stages.

FYI -- the 650 uses bolts instead of studs and nuts.
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Offline Calaya

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Re: 1981 CB650 engine rebuild question
« Reply #2 on: March 13, 2017, 11:19:28 AM »
Thanks, guys.  So a little light oil on the bolts is fine?  Any problem with anti-seize, as the steel bolts are going int an aluminum head. Of course, when we're finished with the bike it won't be sitting outside like it had previously, which was probably 95% the cause for such oxidation/rust.
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Offline SOHC4 Cafe Racer Fan

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Re: 1981 CB650 engine rebuild question
« Reply #3 on: March 13, 2017, 02:14:42 PM »
I don't know if I'd want to use even the blue Loctite.  If you have the need to remove the head or cylinders in the future, and you are using stock bolts (as opposed to heavy duty studs on a 550/750), why make them tougher to remove?  I get that it has sealant properties, but especially if Calaya is reusing stock bolts, I wouldn't want to subject them to unnecessary extra stress.
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1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline Calaya

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Re: 1981 CB650 engine rebuild question
« Reply #4 on: March 14, 2017, 08:23:52 AM »
Thanks for the info and perspectives.  I think we'll just put them back in without any lubricants, especially since the manual doesn't specify to use anything.  While my experience is that most manuals err on the side of caution, I wanted to check with the real-world experiences of members on this forum.

I really appreciate the willingness of everyone here to share their expertise.  I makes a world of difference on a project like this.
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Offline Gwindt

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Re: 1981 CB650 engine rebuild question
« Reply #5 on: June 01, 2019, 12:02:04 PM »
You will definitely want to oil the threads.  Use a pipe cleaner to clean out the bolt holes or same size tap set.  Torque specs are for oiled bolts not dry...  I learned this the hard way on my 81 cb650c and snapped a head bolt off.  Big nightmare having to drill out the broken stud.  Then finding new replacement head bolts was a nightmare.
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