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Author Topic: Valve Cover Screws Stuck  (Read 3367 times)

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Offline kmk108

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Valve Cover Screws Stuck
« on: June 17, 2015, 11:05:27 AM »
Hey everyone!

I'm rebuilding the top end of the motor on my '74 CB750. I've got the engine out of the bike and ready to work on, but I can't start work on the engine. I can't get the valve cover screws to budge at all. I was able to get the center cam cover off by using a vice grip to break the seal, but I can't fit the vice grip between the screw and valve cover on the others to get them off.

I was able to get one by using a screw extractor and using the vice grips to turn one, but it hasn't worked on the others. I can't get any lubrication down the threads. From what I can see, it's stuck toward the bottom of this couple inch-long screw.

What should be my next step? I have no problem ruining these screws to get them out. I'll replace them during the rebuild.
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Offline CBGhia

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Re: Valve Cover Screws Stuck
« Reply #1 on: June 17, 2015, 11:17:08 AM »
Quote from: kmk108 on June 17, 2015, 11:05:27 AM
Hey everyone!

I'm rebuilding the top end of the motor on my '74 CB750. I've got the engine out of the bike and ready to work on, but I can't start work on the engine. I can't get the valve cover screws to budge at all. I was able to get the center cam cover off by using a vice grip to break the seal, but I can't fit the vice grip between the screw and valve cover on the others to get them off.

I was able to get one by using a screw extractor and using the vice grips to turn one, but it hasn't worked on the others. I can't get any lubrication down the threads. From what I can see, it's stuck toward the bottom of this couple inch-long screw.

What should be my next step? I have no problem ruining these screws to get them out. I'll replace them during the rebuild.

Do you have an impact driver?  That is about the only way to get these out.  If you already buggered the heads,  then I would try left handed drill bits.
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CB550 Cafe, GL1000, Buell Ulysses
Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

Offline PeWe

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Re: Valve Cover Screws Stuck
« Reply #2 on: June 17, 2015, 11:19:24 AM »
Original screws were horrible! Thats why I have 2 impact screwdrivers. Hit it with something heavy. A std hammer as carpenters use is not enough¨. 5lbs or similar.

The screws you cannot remove this way, drill head off. All done lift cover and use a grip to remove the remaining studs. Good idea to inspect all threads in head and use helicoil or similar where needed.

I replaced all X heads with allen heads
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline 70CB750

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Re: Valve Cover Screws Stuck
« Reply #3 on: June 17, 2015, 11:22:42 AM »
Impact driver is $25 or so at Sears, quite worth it.

Important is to preload the impact drive, push down, turn it CCW to eliminate play and hit it with a hammer.  Works everytime.
« Last Edit: June 17, 2015, 11:43:16 AM by 70CB750 »
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Prokop
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I love it when parts come together.

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2006 KLR650

Offline flybox1

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Re: Valve Cover Screws Stuck
« Reply #4 on: June 17, 2015, 11:25:38 AM »
are hammers ever a good thing with these bikes  ::) ;D
just drill it off.  once the cover is off, you can get some pb blaster around its threads and grab it with some vice grips.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline 70CB750

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Re: Valve Cover Screws Stuck
« Reply #5 on: June 17, 2015, 11:45:36 AM »
Drilling a steel bolt head out of aluminum?  So when the drill bit slips he makes a hole in the cover?  And than vicegrips, the marvel of precise engineering?

Brilliant! ;D

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Prokop
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Pure Gas - find ethanol free gas station near you

I love it when parts come together.

Dorothy - my CB750
CB750K3F - The Red
Sidecar


CB900C

2006 KLR650

Offline flybox1

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Re: Valve Cover Screws Stuck
« Reply #6 on: June 17, 2015, 11:52:43 AM »
haha...yeah.  just as precise as a BFH!  ;D
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline DaveBarbier

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Re: Valve Cover Screws Stuck
« Reply #7 on: June 17, 2015, 01:05:31 PM »
I have drilled quite a few screws out. Works very well as it's usually the head that's stuck, the threads usually come out quite easily. Since the screws are a + shape they hold the bit centered well. The head usually breaks off and you can pull out the threads like Flybox said after you lift off the cover. Or, use left handed bits and it'll come out completely in one go. Later today I'm going to be drilling the heads off my oil pump screws this way in my 650.


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1978 Honda CB550K
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Offline PeWe

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Re: Valve Cover Screws Stuck
« Reply #8 on: June 17, 2015, 01:37:22 PM »
I have drilled some too when I thought that a heavy hammer should cause damage.
This had bad x-screws, did not dare to use a heavy hammer here.
http://www.cmsnl.com/honda-cb750k6-four-canada_model14381/holder-shaft_23150300010/#.VYHZMkb5MSk
Small drill to start with, like 3mm, then a bigger, maybe 5mm, in the end same size as the head of the screw. Did not damage any alu.
Countersunk Allen  screws used durig assembly.
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline mrfish2

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Re: Valve Cover Screws Stuck
« Reply #9 on: June 17, 2015, 02:24:23 PM »
I use a Dremel with a cut-off wheel and just cut the heads off the screws. Heat works well too, haven't seen anybody mention that yet. Just take a propane torch (the kind that come in a bottle about a foot tall) and heat that sucker up, then use an impact drill or cut the head of the screw off.
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1976 CB550K            1979 XS1100
1980 CB650C - Sold

Quote from: crazypj on October 19, 2008, 09:14:45 PM
It's a little motor and likes having the tits revved off it.

Offline DaveBarbier

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Re: Valve Cover Screws Stuck
« Reply #10 on: June 17, 2015, 05:28:05 PM »
If you're going to drill, I'd use a bit the same size as the shaft, not the head...oh god, what have I done?!


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1978 Honda CB550K
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Offline przjohn

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Re: Valve Cover Screws Stuck
« Reply #11 on: June 18, 2015, 08:16:38 AM »
If you are heading for the Vise Grips that early in your work you may seriously want to assess your abilities. Patience is a virtue.
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