Undoing an aluminium to aluminium thread?

**Dodo** · 30th April 2010, 15:50

Hey everyone, i am looking to open the rocker cover on my yamaha sx-4 which is an aluminium cover onto the aluminium head and simply put i cant get it off and am hoping for advice.
Heres an image of what it looks like:

It has a 24mm hex on the rocker cover which unfortunately is also aluminium (as its all one piece) so will be very easy to damage. I have a decent 24mm spanner and with that have managed to dent the aluminium while trying to undo it already so dont think i will be able to apply any more force without seriously damaging it.

The aluminium on the bike is quite oxidized and i am wondering if the rocker cover cover and head have fused in some way or something? and if so does anyone know of a way to remedy this before i try again?

Any help would be appreciated,
Thanks,
Joseph

**marty** · 30th April 2010, 15:59

Use a 24mm 6 point socket - 1/2 drive if you can fit it in. That should move it. Could try some heat (heat gun - not hair dryer) or squirting CRC over it and leaving it overnight before heating and turning.

A normal spanner will just fuck it up, but if you can't fit the socket in there, find a 6 point ring spanner and file/grind the base of it flat so it sits flush with the cap - there's not a lot of purchase there.

**neels** · 30th April 2010, 16:06

Gently tapping with a hammer around the outside of it to loosen the threads might help.

**Latte** · 30th April 2010, 16:12

CRC Would help

**Dodo** · 30th April 2010, 16:25

thanks for the reply guys, i have a 12 point ring spanner and a 12 point socket. I will have a search around the shops in the next few days for a 6 point round spanner or socket though will admit I was hoping to avoid the costs of buying more tools ;-)

I've given it a good dousing in CRC but not much luck there, and have tried tapping it with a hammer as well, will try use a corrosion cleaner on it before I tackle it with another tool.

If anyone in Wellington had a 6point 24mm socket of spanner they would be willing to lend me for 15 mins that would be greatly appreciated!

**Ocean1** · 30th April 2010, 16:31

Straight torque might not be the go, a 1/2" rattle gun will almost certainly have it off in about 2 seconds.

Means removing the engine, but if you fuck the cap you'll be doing that anyway...

**Max Preload** · 30th April 2010, 16:51

Heat. Just running the engine may suffice.

Originally Posted by Dodo

...will try use a corrosion cleaner on it before I tackle it with another tool.

Be VERY careful about using anything corrosive on an aluminium alloy thread, or any other metal for that matter. You may well make it worse. Besides which there will no doubt be an o-ring under the head anyway.

**HenryDorsetCase** · 30th April 2010, 17:01

I was reading somewhere online that aluminium oxide (which presumably is the cause of this lock) wont shift with oil, but acid will dissolve it: vinegar was suggested it. Ive been meaning to try it with a tatty old engine cover or something.

Anyone know: the source seemed reasonable but it was online:notoriously unreliable.

**Cloggy** · 30th April 2010, 17:03

Yep, these are really tight if this is the first time it is being undone. I undid mine with a 12 point ring spanner without any damage though. I just fitted the ring spanner and gave it a couple of gentle blows with a soft mallet.
Quite a fine thread on these plus a rubber o-ring if memory serves me right which doesn't help with getting it moving in the first place. Removing the fuel tank for ease of access helps as well if you haven't already done so.
When you do get it off, be careful fitting it back on as they are easy to cross thread.

**HenryDorsetCase** · 30th April 2010, 17:03

a ruffian might use a big-ass Stilson around the outside of the cap, after he'd ruined the hex. Not that I have ever grom-wrenched anything that badly. OK well I have. but I wouldnt now. Well i might. But I probably shouldnt.

**Katman** · 30th April 2010, 17:36

When all else fails and the hex is fucked it's time to break out the hammer and cold chisel.

**marty** · 30th April 2010, 17:48

That was my next suggestion, but I reckon the 6 point will do it.

**Brian d marge** · 30th April 2010, 17:52

Heat... as been said is your friend here , Run the engine...... if you cant get the thing hot ( there is from memory a rubber o ring ) then tap ( with a Steel hammer) the Outside of the cover were the thread is don't wail on it and mark the cap , but it will move the thread relative to each other and the whit crap will loosen a little

CRC just make the area oily and slippery ( IMHO )

Failing heat and shock ( can send photos of wife if it needs a big shock)

and the nut is on its last legs ( ie a cover renewal ) Grips , not a mole wrench but one that cams in , or as has been said hammer and chisel ( which if done carefully doesn't make much of a mess)

Patience is your friend here

and if you really want a challenge try the timing inspection caps on pretty much any Honda ,,,,,,,,,

Stephen

**Motu** · 30th April 2010, 19:01

Rather than being corroded in there,it is most likely just stuck on a dry O ring bonded to the alloy...same as those spin on oil filters that you think someone else put on too tight,but in fact they didn't lube the seal.Freezing penetrants like CRC Freeze It or Wurth Ice are the best I've been using the last few years.For the stuck O ring - chip the edge off the cap,it's pretty thin and will expose the O ring.