valve seal replacing

Classic Norton Commando Motorcycles.

valve seal replacing

Postby ludwig » Mon Aug 30, 2010 6:46 am

As promised , for britbike 220 and hungry joe ( and whoever is interested ..) a photo tutorial to replace seals without removing cylinder head .
First of all : I am inventing nothing new here .
This job is done on cars all the time , using compressed air and a special valve retainer removal tool .
This tool can't be used on a Norton , because of lacking space over the valve .
I don't like compressed air because the hissing sound of air escaping somewhere drives me crazy ..
The makeshift tool in the other thread + rope will work , but I believe making proper tools really pays .
The job will be done much easier , faster and safer .
If you ever where to change the seals on a V8 using the rope trick , you'll EAT your rope out of sheer frustration before you are done ..

So let's make the tools first :

T1 : valve spring compressor
T2 : valve stop

bend a strap of metal , or cut from any U-shaped profile , roughly these dimensions in mm :
don't make it shorter , or you'll have troubble compressing the valve spring deep enough
It must be quite strong for stability , but the thinner , the more space you have for fidling with the collar retainers .

The central bolt is about 5 cm long .
because threaded rod with the correct British thread is impossible to find ( for me ) , I made it out of 2 parts , using M5 rod and an old valve adjuster :

If you don't have spare valve adjusters , or have a problem with drilling and tapping the adjuster ( a lathe comes in very handy )
you can also use metric M7 thread rod , it is an almost perfect fit .

The finished compressor will look something like this :

the lower nut is important to prevent the bolt from turning while compressing .

The valve stop also is 2 parts : a drilled out spark plug and a bolt with a lip .
If you find an old plug with a 16 mm hex , it will be more compact :

Knock out the ceramic and centre electode ( wear eye protection ! ) and drill out .( again : a lathe is nice ..)

For the bolt , I used a bolt like pictured , it holds the front brake on the spindle on Mustangs .
Anyone familiar with old Fords will ( should ..) recognise this bolt immediately .
It has the perfect size , but of course any bolt with a large head will do , or weld the lip up .

The chamfer is very important , so that it can easily slip trough the plug hole :
total length minimum 6 cm ( 2.5" ) and lip must stick out about 8-9 mm ( 3/8 ")
Cut a slot in the top of the bolt in line with the lip .
Chamfer one end and mark the orientation of the lip ( red dot )

the bolt must be a nice sliding fit in the plug .
finished tools :

also needed :
12 mm temporary replacement rocker shaft , ' fishing ' hook , centering tool

Now to work .

first step is to remove the rocker spindle(s).
If you don't want to pull it cold , take a short ride first .
remove tank , valve cover and turn engine so that LH inlet valve is down ( to pull RH shaft )
And piston is a few mm past TDC .
Pull rocker shaft and replace with a 12mm rod ( cut bolt , drill bit ..)
Turn the engine 360° and do the other one .

Let the engine cool down if it was warm , then remove the plugs and slide loosely assembled T2 in the plug hole .
Turn the hollow plug in a few turns , turn the lip towards the valve stem and finger tighten the lock nut ;

From the inside , it will look like this :

remove the valve cover stud , using 2 nuts :

Now remove the valve adjuster and install T1
if you have mushroom adjusters , use a thin rod ( see later ) in place of the rocker shaft so that you can lift the rocker up sufficiently to remove the adjuster bolt :

Compress the valve spring .
If the retainers stick a little , a tap on the spring collar will break them loose .
Compress further , till you can remove the 2 retainers .
A magnetic screwdriver is handy .
To magnetise it , rub it over a magnet .


Remove T1 (threaded rod can be left in place )
Now , if you don't mind fidling with spring washers and shims in tight places , just remove the rocker arm completely .
If you prefer to keep the rocker arm in the head , go to the next step :
loosen T2 and turn it 180 ° so that you can lower the valve against the piston .
( it wàs a few mm past TDC , remember ? ..) :

Replace the temporary 12 mm rocker shaft with a 4 mm thin rod .
This will allow you to push the rocker just enough out of the way to remove the springs :

Once the spring is out , keep the rocker up with a rubber band , or something .
You now have free access to the seal :

Replace the seal ( No picture , I am not so crazy as to remove a perfectly good seal ..)
Reinstall spring .
Pull the valve back up , Turn T2 back 180° dir valve and tighten .
Note : If the valve has dropped too deep to catch it with pliers , remove T2 and pull it back up with a wire hook trough the plug hole .
Reinstall collar , T1 , compress , install retainers , etc ..

Here you see why it is handy to use a temporary 12 mm rocker shaft :

The spring collar will push up against the rocker arm , so you'll have to press it down a little , while centering the rocker and shims with the centering tool and than place the loose fitting 12 mm shaft .
Installing the proper rocker spindle at this stage would be difficult .
You do this best after the collar retainers are in place and T1 is removed .
Mind the correct orientation : oil hole towards the valve .
Adjust valve , remove T2 , turn engine 360° and do the other one .

Two other jobs worth considering while you are in there :
replace rocker spindle covers with one piece ones with real lip .
drill trough inlet spindles to get rid of the cross over oil line ( tough cookie : if you don't have a lathe, forget it ..) :

With the right tools you can do both seals in 2 hours easily .
It took me longer to take the pictures and type this tread ..
That's all folks .
Any questions ?

If not , happy tinkering ..
Last edited by ludwig on Wed Sep 01, 2010 11:54 am, edited 14 times in total.

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Re: valve seal replacing

Postby britbike220 » Mon Aug 30, 2010 9:27 am

Very clear and it answered all of the questions I had, many thanks Ludwig. I will download and print your thread as a supplement for my manual, thanks again.

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Re: valve seal replacing

Postby slimslowslider » Mon Aug 30, 2010 10:15 am

Ludwig, thanks for the effort taken to share this.

Fellow Norton rider got stranded on the way back from the INR in Spain with a broken valve spring.
He still is waiting for the bike to be transported home.
Had he had your tools, and a spare spring of course, he could have repaired it on the spot.

Looks like another set of special tools I am going to add to the onboard toolkit.

Another thing one could consider to do at the same time is to tackle any rocker/valvestem misalignment (brass shim instead of spring washer).

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Re: valve seal replacing

Postby swooshdave » Mon Aug 30, 2010 10:16 am

Very nice.
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Re: valve seal replacing

Postby cash » Mon Aug 30, 2010 11:56 am

I've had my bit of kit for nigh-on 20 years it's nowhere near as well developed as yours. It started life as an old box spanner a length of screwed bar, an old spark plug and a tyre lever. I've changed a few seals etc during those 20 years and never ever thought of leaving the rocker in place. :shock:


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Re: valve seal replacing

Postby Hungry J0e » Tue Aug 31, 2010 12:47 pm

Very nice! Can this be flagged in technical documents or anything?

Seen here are the two special tools I used. The top is a rocker shaft slide hammer sold by Commando Specialties (and perhaps others) that I picked up awhile ago on sale. The bottom is my version of the homebrew spring compressor. Similar to the ones previously posted, basically an old rocker shaft cover with a hole drilled in the center. I also placed two jam nuts at the base of the bolts to provide wider "feet" so they wouldn't slip out when compressing. Definitely cruder than Ludwig's tool, but still works a charm.


After popping off the collets, I pulled the rocker shaft and then removed the arm. As expected, the inlet valve cover was riding the valve shaft. Unexpectedly, I also discovered the inner spring was broken. This could possibly explain some of the issues I've been having with that cylinder. Paul is sending me a spare spring, even though I'm well outside the warranty period!

If I had to start all over, I would do as Ludwig recommends and pull the rocker shaft first, replacing it with a smaller diameter shaft and leaving the rocker arms in place. Not looking forward to reassembling the rocker arms and associated shims in that tight space.


- HJ
Last edited by Hungry J0e on Tue Aug 31, 2010 3:59 pm, edited 1 time in total.
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Re: valve seal replacing

Postby RennieK » Tue Aug 31, 2010 2:13 pm

Thanks Tons for your excellent post Ludwig! You should win a prize for adding it to the site here!

Jerry / L.A.B. a tech tool section would be great to group these things together on.
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Re: valve seal replacing

Postby preston » Sun Jan 20, 2013 1:46 pm

hi any ideas this is the second time i have the good seals with the spring the left side is good the right side keeps coming off so it smokes on decel fouling plug i have it apart dont see any thing damaged any sugg. before i put it back together thanks

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Re: valve seal replacing

Postby preston » Sun Jan 20, 2013 4:43 pm

to late put back together fired it up first kick no smoke thank goodness!!! see how it goes chow for now mike

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