Spark plus with a hex smaller than 18mm?

[alexdecker]

This might seem like such a stupid thing. But I’ve bought and tried five different spark plug sockets now, and can’t get anyone to fit down plug 2 and 3. Is there a spark plug with a smaller hex size than 18mm that would work, or can someone link to a socket that can actually fit in there?

[SteveD CB500K0]

This comes up every now and then.

Honda made a special plug spanner.

I had a Halfords 1/2” square drive plug socket turned down by a mate with a lathe.

Steve


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[mickwinf]

I use a 3/8 drive 18mm socket which is slim enough to fit, i find the number 3 plug is the problem due to the tacho drive getting in the way so i ground it down on my bench grinder to fit. Used with an extension with a wobble end which gives a bit of angle adjustment.

[taysidedragon]

Would an old-fashioned box spanner work? They have thinner walls.
Obviously a proper plug socket is better, but needs must.

[Bryanj]

Snap on 18 mm 3/8 drive deep socket will do the job

[SteveW]

I got a set of these, they fit perfectly.

[Oddjob]

Snap on 18 mm 3/8 drive deep socket will do the job

Yep, that's what I used back in the day. Even fitted a small rubber ring inside to protect the porcelain on the plug.

[SteveD CB500K0]

Ordinary box spanners don’t have the rubber plug retainer in them.

Without that it’s quite difficult to get the loose plug out of the central cylinders.


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[deltarider]

Best tool for the sparkplugs is the Honda one. If not in the toolbag under the seat, it is still available for a reasonable price at https://www.cmsnl.com/honda-cb550k3-four-germany_model14674/wrench-plug_89216323000/
This is what has worked best for me. Before I mount a sparkplug, I screw the little ferrule on top, some non OEM plugcaps require, but... just a few turns. Now press the plug in the Honda tool, so the rubber, high inside that tool, will have a firm grip. The sparkplugs hexagon is now exactly where it should be and the whole combination is stiff and easy to work with, meaning the plug will not fall out. Screw the sparkplug down and tighten. Withdraw the plugtool and then simply remove that ferrule again. On removing the sparkplugs, do the opposite: withdraw the plugcap, carefully avoiding a too wild movement of your hand that may result in a compromised connection cap - wire or even wire - coil. Then screw the little ferrule on top of the plug - a few turns is enough - and firmly press the Honda tool on it. No risk of damaging the porcelain and guaranteed no more prematurely falling sideways of the #2 and #3 plug, which would result in a hassle to get them out.

[alexdecker]

Best tool for the sparkplugs is the Honda one. If not in the toolbag under the seat, it is still available for a reasonable price at https://www.cmsnl.com/honda-cb550k3-four-germany_model14674/wrench-plug_89216323000/
This is what has worked best for me. Before I mount a sparkplug, I screw the little ferrule on top, some non OEM plugcaps require, but... just a few turns. Now press the plug in the Honda tool, so the rubber, high inside that tool, will have a firm grip. The sparkplugs hexagon is now exactly where it should be and the whole combination is stiff and easy to work with, meaning the plug will not fall out. Screw the sparkplug down and tighten. Withdraw the plugtool and then simply remove that ferrule again. On removing the sparkplugs, do the opposite: withdraw the plugcap, carefully avoiding a too wild movement of your hand that may result in a compromised connection cap - wire or even wire - coil. Then screw the little ferrule on top of the plug - a few turns is enough - and firmly press the Honda tool on it. No risk of damaging the porcelain and guaranteed no more prematurely falling sideways of the #2 and #3 plug, which would result in a hassle to get them out.

Nice thanks! Going with this 😊

[Oddjob]

The CMS one isn't the correct one. The correct one is the one which came with the tool kit, it has a knurled end so you can spin it with your fingers and it's got a small waisted section which helps avoid the tacho drive. It's far thinner than the linked one, which will work but not that well on the No3 plug.

We used a telescopic magnet to remove any plugs that fell sideways, never failed.

[mickwinf]

I have one of the honda ones and the hexagon part spread out so too loose on the plug

[peterengland]

I just bough an off the shelf jointed plug spanner from Halfords, it fits fine