Lead free valve seats on a Lightweight- is it worth it?

Something that has crossed my mind, won't be doing it until the seats have recessed beyond serviceability, hopefully a long time in to the future!

The problem with the lightweights is that (I think) the seats are cast in place, that is to say not a press fit.  The only way to replace the seats properly is to machine the cast in seat completely away, fill the pocket created with weld, then machine a suitable pocket for a pressed in seat of suitable material.  Otherwise the outside radial thickness becomes excessive.  The cast in seat will have a "reverse" angle on it outside diameter to hold it in place.  Therefore the diameter that cannot be seen will be somewhat larger than the visible outside diameter.  

For the work I have described £350 seems reasonable, £60 -70 per seat for pressed in seats seems to be typical.

I'm sure someone will be along shortly to say they've had new seats pressed in and its okay........

What must also be considered, with an upgrade like this, is the possible knock-on effect with regard to other moving parts in the valve train.

When fitting lead-free valve seats started to become popular in the 1980s, owners found that valve head faces were picking up on the new seats due to a material incompatibility. This could be sorted by a change of valve material but that in turn led to a material compatibility issue with the valve guides. 

Perhaps a replacement cylinder head and a bottle of Lead-Sub might be a cheaper solution.

Michael, John,

Steel inserts in an alloy head so no welding involved. I believe past comments have indicated that the valve seats fitted as standard in the lightweight are fine with unleaded fuel.

IMHO you would be wasting your money and risking your cylinder heads in getting the valve seats replaced with a material that may or may not be superior to the centrifugally cast grey iron specified by Norton.

I refer you to https://www.nortonownersclub.org/support/technical-support-general/unleaded-petrol-more

Is there anyone out there who has had the valve seats replaced on a lightweight because of recession caused by lead free petrol?

My own experience has been without problems for many thousands of miles. I always use a premium grade of petrol if available at the station, but this is to protect my tank and carburettor from corrosion when the bike is laid up. I may be wasting my money, but I know it can't be worse than the cheaper stuff.

Good luck with the rebuilds.

Peter

... several hundred pounds getting unleaded seats in my Commando. As I discovered later with a Triumph Stag, inserted seats in alloy heads are fine. As far as I know the only reported problems with seat recession have been with cast iron heads where the seats are part of the parent metal. The FBHVC did test on a BMC A series engine with such seats and actually it was OK till run at high revs for extended periods.

In blissful ignorance I run my Jubilee on unleaded petrol with no additives and so far I have had no problems, As you say, if yours is a weekender bike you probably won't rack up many miles, like me.

I only paid £400 for my bike though I have spent about £2K on getting it restored The cost of new valve seats seems excessive. Also, I just picked up two used heads for £20 with good valve seats!

Dennis

Michael,

For what it's worth I have clocked up over 4000 brisk miles over 2 years on my Navigator running on premium unleaded with original valves and valve seats and over 38,000 miles of 'spirited' driving over 25 years in my Triumph Vitesse with original valves and valve seats without the slightest hint of valve seat erosion.   On that evidence I have yet to be convinced by all the 'unleaded' doom and gloom put about by the industry when I restored the Vitesse back in the mid 90s!   It has saved me well over £1500 on unnecessary engineering work.   

Good luck with the Electra, I still hanker but the Navigator is still too much of a joy to change it!

Nick 

Waste of time. I run about in a Reliant which has been modestly tuned and used 'spiritually' for many years. After 45 000 miles a head inspection showed that the exhaust valves were beginning to pit but valve seats were fine. My own Electra-never even thought abut unleaded petrol. But electronic ignition does such wonders for engine smoothness and running temp that is more in keeping than worrying about unleaded valve seats-waste of money.

IMHO it would be a waste of money. Very few engines had problems with valve seat recession when unleaded petrol was mandated. Those  few that did had cast iron heads and no seat inserts. BICERI did an extensive test program and found that the A series BL engine could, if run under unusual conditions, suffer from this problem, but this was exceptional,

Save your money for a better cause.

DO NOT DO IT!

You already have valve seat inserts!

hello Norton made there motorcycles with valve seats for export machines witch all light weights had for ethernol or ethyl in the USA and other country   So there is No need to replace them if they're in good order  But if Pocketed   beyond  cutting then and only then do they need replacing  and do use bronze valve guides  there better  yours  anna j  

I'm not sure I agree with some of the points raised here.  One point I would agree with is leave well alone until something needs to be done.

What happens when the valve seats are pocketed so badly the head is beyond use?  There will come a time when finding a serviceable head becomes impossible so the seats will need to be replaced.  This, for the lightweights, will be an expensive business if its done properly. 

hello now when its time for machining valve seats  the machinist will normally set up the head on a mill drill and machine out the old valve seats  to remove them and then fit a new ones by heating the head in a industrial oven for a interference fit then when cool then remeam out the guide holes and fit new bronze guides and then recut the valve seats to match the new valves then lap them in and test for leaks by setting the valves in place and poor some white spirits in with a blue engineers dye and the leave of a half hour and then check for leaks  if everything is dry then then on to the next stage after cleaning of fitting the valves and its springs  and oil with assembly lube  job done  As I have been this machinist  and do have my own tooling to do this job when needed            ,yours  anna j 

You can buy a tin ball for a few quid that goes in the tank, never need to add additives again. Maybe a waste of money who knows, but after reading the above comments looks like the light weights don't need it anyway but thought I would mention it

.. completely wasted in my view. I'd like to hear from anybody who has actually suffered valve seat recession due to unleaded fuel on a Norton with an alloy head (or for that matter an iron one - my ES2 seems fine.....)

I’ve got enough s/h cylinder heads to last me into the next century, assuming I were to live that long! 

Dan