Here you go no more broken fins or knackered threads just buy new!!

http://www.ebay.co.uk/itm/BSA-M20-CAST-ALUMINIUM-CYLINDER-HEAD-/201236092952?&_trksid=p2056016.l4276

That looks pretty good to me from the photos...and at the asking price of £140 not unreasonable for a new piece..Ian

Possibly sourced from this supplier from India? http://www.ebay.com.au/itm/111472574814?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

He actually stipulates that it's "British made" Ron

email (option): ronpier@talk21.com

And by the looks of the chattermarks on some of the spot facing , made with original BSA tooling as well. not sharpened since 1942

email (option): wariron@tpg,com,au

Maybe he should have changed the combustion chamber and spark plug position for some extra power !

Yes, he wasn't using much imagination. Pity.

You can limit your market for parts by 'upgrading' them..

Many people will only buy 'standard' spec. parts as there is a great tendency to want to keep everything original...even if it's not the most efficient or durable way...

For example, many here wouldn't dream of buying any of the stainless parts I make, even though it is obvious they will outlast any plating job when in use....

It is the case that for many originality outweighs any practical consideration...

I think the chap has done the sensible thing by making a 'standard' part...Ian

Most of us are capable of making a reasoned judgment on the use of stainless fittings (contrary to what you might think, I'm not dead against it, my Commando is full of it..) In the case of my WD bike, I didn't consider it correct for my needs and what I had in mind...

However, in the case of a 'tuned' cylinder head that has not been subject to independent testing or to widespread use, there would very much be a feeling of experimentation. I've seen too many ported heads that made bikes slower or less tractable, not to mention a decrease in reliability...

Tuning is fine for those who want to do it...but in the case of WD bikes, many will be looking to replicate the original feel and experience...How can we otherwise judge whether they were really as slow as everyone says...?

I must say though, that M20 owners in particular do seem to be those who feel the need for more power than came out of the factory...Has anyone actually put a standard M20 on a dyno ?

I'm all in favour of stainless parts after years of frustration with the quality of plating. I've had a few special shaped 16H bolts made out of stainless, once lightly blasted they look exactly the same as the dull plated ones. Buying an original of one of the bolt cost me more than copying it in stainless. I should sell the original to get my money back.

email (option): horror@blueyonder.co.uk

I've had my M21 plunger on a dyno at a VJMC dyno day and it produced a massive 11 hp at the rear wheel.

11bhp at the back wheel would be about right for an M21..The factory quoted figure of 15bhp was measured at the engine and it is generally accepted 4-5bhp will be lost in the transmission etc...

At least it seems BSA were pretty honest in the figures quoted, which is more than can be said for many 'modern' manufacturers who blatantly 'inflate' the power output of their machines...

It is true that deviating from the original state of tune will alter the essential experience of riding the machine in the form it was made...and there is a good argument for not doing it in some cases...

Personally more than half of the 100,000 plus miles I have covered on my M20 was done with a standard engine, so I feel quite happy that I am fully conversant with the original concept...

As I don't trailer my bike and ride it to wherever it has to go I would rather trade the 'original experience' for more power and a shorter and easier journey...That's just me though...

Regarding 'upgrades' of any type the fact is most M20 riders don't have them or want them...For example, of the 50 or so M20s in Normandy I would estimate only 10% had any work done on them to alter their performance...

Likewise with stainless fasteners..As I don't run a car and my bikes are used for my transport they end up getting ridden in the winter, when the roads are salted and there is frequent rain...

Looking at it practically therefore, for me the use of stainless is a 'no brainer'...It's either that, rusty fasteners or frequent trips to the platers and additional work on the bikes...
It's not for everyone though, or in every circumstance...

So, coming back to the question of the replica head I would argue the chap made absolutely the right decision if he wants to maximise the potential number of customers...

Not that many of those will be WDM20 riders...Their bikes never had the alloy head fitted.. ...Ian