Forum

[Mark M]

Valves don't seize in their guides because of a lack of lead in the fuel, they seize because of a lack of lubrication, your mechanic should know better! The tightness of the valve is clearly an issue but you need to check lubrication there too.
REgards, Mark

[Dennis C]

It looks like Graham does not know the history of this bike, also the "good mechanic" is unsure of the cause, as Mark M states lack of lead is unlikely to be the cause, a half MM oversize stem will not fit a standard guide as the clearance on a valve stem when new is only 1 to 2 thou a valve stem needs almost no lubrication check out the stem seals fitted to modern engines to prevent any oil getting in there, as I said before a stainless steel exhaust valve in a cast iron guide is a recipe for disaster and will pick up and jam the valve, take a look here. http://www.alpha-bearings.com/Valve%20cat/valvehp.htm

[Alan R]

Hi guys---------- PHIL, MARK, DENNIS, with you all the way guys !!------since learning in the "School of Hard Nocks" in my Grass-Tracking days ( 176, Southern Centre ACU)I now fit Phos.Bronze guides to all my road going, petrol powered Enfields as a matter of course....My No.1 bike also has the Big Head exhaust valve but it had issues with small, metallic deposits appearing on both faces after several thousand miles...It was returned to the manufacturer via our hosts for inspection.......I received it back later with the comment that these were due to me using the cheaper fuels/oils with a high ash content..... I removed the deposits, reclaimed the seat profile in my lathe and re-fitted to an overhauled, spare head......The bike went back into service using ONLY premium fuel BUT...... the big-end is now growling, so we'll have to wait a bit longer for the outcome of that trial.....Incidentally, I use a guide stem seal on the inlet but NOT on the exhaust.... indeed I try and have an extra "thou" available to ensure that the HOTTEST part of the whole bike gets some lube...must be working as there is a small carbon deposit at the bottom of the stem----- I can live with that...... PHIL, if you want "Cool Runnings"----(sorry, couldn't resist that)------lets both go onto 100% Methanol at 15:1 CR (as per my "grass" C15)---- I ran it with a 4" inlet tract that regularly frosted up !!-----------------GRAHAM, where did you get this "Pattern" Exhaust part from ??--not our hosts I would wager ??............. The old Tetra-Ethyl Lead was within the PETROL FUEL to help improve combustion, etc and therefore NOT in the lube oil, so played no part in valve stem lubricating--- the nearest it would get was as a layering on the valve SEAT........If you were getting petrol on your valve stem then you were in trouble I would say !!!........

[Graham]

Thanks for the comments (back a bit now). My ref to half a mil was in Imperial parlance, not mm !! Enfield valve guide tollerances are very slack but not that much!
The pattern that I unwittingly bought was from a dealer who h is now no longer an RE stockist (with the new importer arrangements) sio no need to name them as on one else can make that mistake now.
I replaced the parts eventually with Hitchcocks best and so far all has run well (and the bike, 99 Clubman, does get run hard, usually at 70, more when it can).

[loco builder bri]

"imperial parlance" is in Thousanth's of an Inch. Half a millionth of an Inch oversize on a valve stem would not matter.

[Mark M]

Graham, thanks for coming back, great to hear that the problem has been solved and you are happily back on the road again!
REgards, Mark