Bolt removal problem head

I am trying to pull the cylinder head, but there is one pain in the ass that I can't seem to get off. It is the nut in the center of the head, underneath the carbs. The attached pic has the rough location, in red. I tried a 9/16, 1/2, 13mm, and 14 mm. The 1/2, 13mm are too small to get over the nut, but the 14mm and 9/16 are too big and are in danger of rounding the nut out. I have ZERO clearance to get an adjustable in there, nothing gets a bite.
What do I do?????

It is of course a whitworth sized fastener.
While some AF and metric will work on these, there are some sizes that ONLY a whitworth sized wrench /spanner will touch. Search your toolbox again ! Hopethishelps.

flcmbt said:

I am trying to pull the cylinder head, but there is one pain in the ass that I can't seem to get off. It is the nut in the center of the head, underneath the carbs. The attached pic has the rough location, in red. I tried a 9/16, 1/2, 13mm, and 14 mm. The 1/2, 13mm are too small to get over the nut, but the 14mm and 9/16 are too big and are in danger of rounding the nut out. I have ZERO clearance to get an adjustable in there, nothing gets a bite.
What do I do?????

Click to expand...

The head fastener hexagon size is 1/4 Whitworth or 5/16 BSF (0.525", 13.34mm).
http://www.sat.dundee.ac.uk/~psc/spanne ... Size_Table

Most of us have a special spanner/wrench we have ground to fit that nut.

If a 1/4 Whitworth wrench is not easily available then grind a cheap 13mm wrench to fit, 14mm is slightly loose.

For decades now I have a 13mm box end wrench I keep for that purpose.

I used my bench grinder to take off material around the outside of the box end so it will slip over and have enough room to turn the nut.

I don't recall having take any metal off the inside of the box end, the part that actually contacts the nut.

I do know that my 13mm is very tight fit on the nut but seems ok once it gets over the nut.

If your 13mm, nicely ground down around the box end will not slide over the nut then take a dremel and take just enough metal off the inside edges, just a little should do it.

Then keep that special wrench forever.

A "6 point" 9/16 box wrench will do it.

The two end size bent half moon special spanner is made for this and well worth it to keep handy for as long as you are into Nortons. Lets ya work around frame and exhaust, air box, etc. easier than a straight wrench.
13 to 14 mm fits on the 1/4" Whitworth but is best to try both for best fit as often better than the 1/4" Whitworth itself, ugh. 9/16" fits a lot of fasteners better than Whitworth.

I find the 13mm too tight on mine, and the 14 too loose unless it's jammed tight against the barrel. Best to get a 1/4WW and grind it down unless you have something else that fits fine. The ring will need to be ground down to go in that area, in any case, you will have a special tool. I agree, 6 point tools work better, but they're not always available when you need them. Luckily I have a whole set of SnapOn 6 point sockets, they're great.

Dave
69S

Re: rear head NUT removal problem

There is practically NO metric hardware on a commando. Put all metric tools away.

My 2 cents, people who suggest metric wrenches on a norton commando are not your friend. :roll: I have had to fix others butchery on this nut so.... "been there done that ". (I seriously edited/toned back my original remark)

You own a norton and want to work on it...You usually have to make a 1/4W thin wall special box wrench . Make the tool because you can rarely find a correct one to buy. The rear head nut on a commando is a piece of cake compared to some earlier norton heavy twins. The wrench wall should be .045"-.040" wall...and will then work on atlas too.

Commando have a mix of SAE and BSF whitworth and CEI unfortunately in the short years of the commando run, the hardware constantly changed. So learn and listen to advice only from same year and series machine.

Re: rear head NUT removal problem

dynodave said:

There is practically NO metric hardware on a commando. Put all metric tools away.

Click to expand...

Except the spark plug. LAB informed me of this little issue. Otherwise I agree completely Dave. Using metric on the Norton is asking for trouble now and later.

Dave
69S

Well cheers guys. I did grind down a cheap 13mm, got it onto the nut but it bent what was left of the wrench. There is room to get a box end if the wall is thin enough. I went on ebay, and found a few claiming to be 1/4 whitworth. Is it worth to check out? I really wanted to be cautious and replace the head gasket as my dad (who bought the bike new, and gave it to me) said it has had head gasket issues in the past. I figured better safe than sorry, and replacing. This is the last bolt I haven't gotten off the head. Frustrating to say the least.

Re: rear head NUT removal problem

DogT said:

dynodave said:

There is practically NO metric hardware on a commando. Put all metric tools away.

Click to expand...

Except the spark plug. LAB informed me of this little issue.

Click to expand...

dynodave did say "practically".

flcmbt said:

This is the last bolt I haven't gotten off the head.

Click to expand...

The #2 head fastener should be a 3/8" - 26 tpi Cycle thread nut? Leave the #1 bolt in position as that should be removed last/ fitted first.

Isn't the oil filter thread metric too? (assuming it's got one).

Yes.

Okay, I play along, the plug thread is metric, but the across the flats hex of the spark plug is imperial, neat eh.
A nice set of open end and ring whitworth spanners are a useful part of your Commando kit. Even doing the valve clearances need old school Whitworth?

Cheers Richard

stockie2 said:

Okay, I play along, the plug thread is metric, but the across the flats hex of the spark plug is imperial, neat eh.

Click to expand...

Well, if you buy a plug spanner or socket these days it's almost certainly going to be metric.

http://www.rhrtools.co.uk/shop2/index.p ... cts_id=472

Rocky Point Cycle sells cylinder head fasteners that have the 26 tpi, but that have SAE sized heads.

RS

Getting back to the problem our member is having. You bent the wrench after grinding it down because as you said it was a "cheap" wrench. I have a number of old Craftsmen wrenches that have been modified to scary thin for various projects and have yet to break one after years of trying because they are made from really good steel. If you grind one down, take it slow, as it is easy to get it so hot that you ruin whatever temper the wrench has. When it starts turning colors or worse red, then you have just softened the metal. If this happens you are better off to heat it to red hot and quench it to harden it. Tempering after hardening is a bit of an art, but heat it to "straw" and quench it again and it should be about right for wrenching. Too hard and it may be too brittle for the job. Try running a file over it, if it sings and won't file it is too hard and will break. If tempered correctly it can be filed but should resist.

If you absolutely can't find the right wrench for the job here is an Alaska bush solution. Smear some good quality lube on the nut, then take your 9/16 or 14mm and smear some 5-minute epoxy inside the ring end and place it over the nut. Let the epoxy get hard and break the nut loose. You should position the wrench to give yourself the widest swing possible. If the lube did the job and you get lucky the wrench can be worked off the nut. If not get out the torch and heat it up until the epoxy gets soft. In bad cases you have to repeat it a few times until the nut gets loose enough to use the "wrong" wrench on it to spin it free.

I'm not saying it is a great idea...but it has saved my butt when I was miles from town and had to work on metric equipment with SAE tools. It has also saved my butt a couple of times when somebody had rounded off a bolt so bad that the wrench would slip on it. The epoxy wont handle a huge load but as long as the gap being filled is quite small it will take quite a bit before failure. Make sure whatever you use will get soft with heat or you just glue the wrench to the equipment!

Russ

Oh yes sorry about the thread hi jack, but LAB all my spark plug sockets are marked in imperial measurements, even a brand new set of good quality Aussie Sidchrome sockets
are marked 13/16 which in metric is 20.638 so 21mm would be close I guess?
Looks like the UK must be more metricated than the Antipodes?

Cheers Richard