Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 Alloy barrel

Hi

Been a while since I first mentioned I was to manufacture an alloy barrel for the A65, well finally made it.
The photo shows a 79mm bore version (not yet Nikasil coated), but can be bored to suit your requirements as with the stroke. The original weighed in at 9.3kg, this one is 3.5kg.
It comes complete with a set of 12.9 grade bolt and studs which are 3/8 UNF top thread.
In my original post I estimated them around 740 GBP. Due to jig and tooling changes I can sell these for 700 GBP plus P/P (no VAT).
I plan to cast another batch in January, if interested or want further information/photo's e-mail me [email protected]

http://i1314.photobucket.com/albums/t565/ecosse_lynx/79mmbarrelrearview_zpsb05b3c14.jpg

look nice..congrats and good luck with them.
joe

Time to save up my nickles and dimes...

They look really nice John, have you tested a set yet? I just had my alloy cyl re-plated and reduced the piston to bore clearance to .002" using Ed V's 79.5mm B44 forged pistons. I've only done 60 miles or so on them but they seem good so far, the thing has loads of power. I weighed my cyls at 9lb 11oz with the outer head studs. I think a big bore alloy cyl with plated bores is such an excellent upgrade for an A65.
Ed V's forged B44 pistons are good esp for long stroke motors because of the shortness of the skirt and where it is. People building long stroke motors need to check where the skirt is at BDC because some piston designs can have it half out the bottom of the bore.

Hi Mark

Not managed to test a set yet. Ordered pistons for Ed and should arrive today/tomorrow.
Know what you mean about the pistons, years ago I had a Norton crank in an engine and ended up with little or nothing below the gudgon pin. I'll e-mail you some other photo's and keep you posted.

These look very nice.
What is the block height and what kind of crank are you recommending?
Is that a breather on the rocker cover?

Lilo

There is sufficient height in the raw casting to deal with all crankshaft and rods configurations that I've considered.
I'll make them to suit what ever you have, 75mm x 74mm or 80mm x 90mm bore and stroke.
In an earlier post I put up photos of a rocker cover breather which I'd made.

Hi

I thought I might have had a few more than four comments/questions out of the 459 views!

John

I would comment that while I don't forsee one of these pieces likely being within my budget, I respect and admire that guys like you are doing this stuff.

I'm with leon. Impressive workmanship but out of my comfort zone.

John; A beautiful bit of kit. Some might be waiting to see how it works and stands up to use.
Gordo

Hi guy's

Thanks for your comments. Gordo, you could be right in that assumption. Hopefully by the end of the month I'll have one up and running in my 650 road bike.
In the meantime I'll be happy to answer any other questions.

John

John also putting up photos on the post rather than a link might get more interest. Sometimes your link opens showing a few views of the cyl in your album and sometimes just the one image?

Hi Mark

Many thanks for the tip. I'll give it a go, although not to good at this. Don't seem to be able to add a photo to a reply, might need to start again!
Managed to get my daughter to help me, that's why it was so quick. See below.

John

[URL=http://s1314.photobucket.com/user/ecosse_lynx/media/79mmbarrelrearview_zpsb05b3c14.jpg.html]test[/url] [URL=http://s1314.photobucket.com/user/ecosse_lynx/media/79mmbarrelbottomview_zps74de90a0.jpg.html]tres[/url] [URL=http://s1314.photobucket.com/user/ecosse_lynx/media/barrelsideview_zpse41b988f.jpg.html]3[/url] [URL=http://s1314.photobucket.com/user/ecosse_lynx/media/79mmbarreltopview_zpsc80bbada.jpg.html]4[/url]

John,
Looking better with the actual images.

Just use the 'enter' key on the keyboard to move each individual image code to the left side of the reply box. And use the 'enter' key to space each image code down a click or two, so they don't look all bunched up. Hit the 'preview reply' option to see how it will look before hitting the 'submit' option.

You can also go into your image thread above and hit on 'edit' and move the images over and make any other adjustments or changes.

The barrels look beautifully machined. Very tempting.

A couple of questions.

1. Does the price include Nikasil and finishing?
2. I assume the followers will run straight in the alloy - correct?

Hi

Yes the price includes the Nikasil coating and the followers run in the alloy block.
Not sure what you mean by finishing! If you can explain, then I'll be happy to answer.

John

I am probably showing my ignorance, but I assume Nikasil has to be surface finished in some way.

hi
Just a small comment from a someone less technical than all others replying to this.
Like many others i have been rebuilding bikes for less than 6 years and appreciate that while some understand the benefits of your alloy barrel not all do.
It may be a good ideal to explain to all the benefits, it may help you.
Thanks Sparky

I'd have to agree with Leon.

It's MARVELOUS to see tinkerers getting more power out of these OLD designs, seeing, AND hearing, changes to the exhaust note.

Nice to read about their exploits and accomplishments.

Successes, failures and rescues.

Thought processes, ideas, and any engineering made during any effort.

Alterations, and improvements.

But, for me, the costs involved are too much.

Why go to a taller set of barrels?

To get length for increased stroke?

This means at minimum, I'd think, new;

barrel[s]

crankshaft

If going for a bigger bore;

pistons, even custom made pistons.

Especially if the stock skirt length has to be modified to clear the crank at BDC...

And, depending upon the new stroke dimensions, there may HAVE to be longer rod[s] bought, and IF the engine is to be actually installed into a racing machine, really GOOD rod[s]?

Maybe a cam must be bought into the "bargain"?

I'm no racer. Any ego trips I've left years ago... I am not implying there are any egos going on here either!

I can go out and buy a MUCH faster, quicker bike... Already in too much trouble, I do NOT need any more of that...

The new bike may even 'handle' better... Once I'd gotten used to it?

But, These are not what this thread is about, it's about the success of someone getting an available successful set of A65 aluminum long stroke cylinder blocks made up in a batch.

For anyone looking for this modification, for street use, or in a racing venue, vintage or not, this is a _GOOD THING_! Saves anyone else from having to engineer and machine the same thing... Again...

For the price of the above components, I'd almost be able to buy another restored bike? At least a whole one.....

For myself, I often think about having a STOCK length aluminum alloy barrel made for my A10 or A65... Think of the weight savings... But the COSTS....

My pockets' depth is limited as it is.....
I am sorry I cannot afford to buy one, for one of my projects, so you can recoup some of your outlay...
It would be interesting to ride one of these altered machines, for CERTAIN!

Hi Rickman

You certainly managed to fill the page, and I'll answer your questions/comments as best I can.

a) The alloy barrel is a replacement barrel for a A65. It can be machined to suit bore sizes from standard 75mm up to 80mm.

b) The barrel height can be machined to suit what ever crankshaft you have, standard 74mm up to 90mm.

c) If the pistons you have in your engine have not see many miles, then you could even re-use these with new rings, true if you go for a larger bore then you need to buy pistons.

These are the main point of you post, the rest it off into building specials and other stuff that I'm not prepared to get into.
Although If someone is building a special feel free to drop me an e-mail and I'll see if the barrel can be machined to suit your requirements.

regards

John

Hi RJG

When the barrels are Nikasil coated they are hone finished at that time, when you get them there ready for fitting.

regards

John

Hi Sparky

In answer to your question. No one presently manufactures replacement barrels for standard bores. After reading on here what Mark Parker was doing, I thought I could take it a step further.

Make a replacement barrel from alloy that would be at least 5kg lighter than standard. Cover standard bore of 75mm up to 80mm.

Have enough height in the casting to allow for the use of longer stroke crankshafts with longer rods.

Be a replacement to cover both the early and later stud base stud spacing's.

Improve on the original by increasing spigot and base flange strength.

hope these answers are of help

regards

John

John; this thread is like a candy store for A65 folks.

For perspective the last time I looked a Pearson Gold Star barrel was over 500 UK pounds and a good piston for it was up around 165 pounds.

Most A65 riders most likely have some decent std and plus 20 pistons that with new rings would fit right into one of your barrels. As well std pistons are usually inexpensive if found as most engines are up at plus 20 or 40 already.

Gordo
It is very tempting for sure.

So, your pistons have to fit the bore? I mean you don't hone the new barrel to fit piston?

Leon; I would expect one would need to specify the exact size needed when ordering.

It does raise the question of how to deal with the next set of pistons once the first set wears out or comes to grief.

Gordo

Hi Gordo

That's right, if you have a set of GOOD pistons, then a new set of rings is all you need. The barrel will then be made to suit your pistons.
Note: Good pistons, I wont do it for pistons that are scuffed, have pick-up marks and generally wore out.

Hi Leon

I have already stated that I don't supply the pistons. I think my reply's above explain that.

regards

John

Hi Leon

I have already stated that I don't supply the pistons. I think my reply's above explain that.

regards

John [/quote]

Yeah, I didn't phrase that well. I meant MY pistons have to fit the bore. So a buyer sends you his pistons? Or the measurements?

Hi Leon

Yes, the preferred way is you send a piston and the coating company measure the piston and make the bore to suit the piston for the correct clearance and best result.
With you being on the other side of the pond, then the other way is for you to send me an accurate size of your piston measured at 90 degrees to the gudgon pin to the third decimal place at its widest point.

regards

John

To make stock and big bore versions, you really only need two bore sizes, as a damaged bore would be restored by replating. It might be worth telling people what you are using when you test and recommending what you know works at what clearance. Pistons vary quite a bit in material, design and skirt taper and rings employed. The B44 Ed V forged pistons I've been using are good value and quality. I've just had my cyl replated to give .002" clearance, about 150miles so far and it seems good.

Using total seal rings with the Ed V (JE pistons) you can get real tight clearances when using a nikasil lined bore (I think the .002" as Mark mentions is what they quote from memory) Not sure about the Standard rings for the JE pistons, but as they use a modern ring design, I imagine it won't be much different.

Hi Allan

What JE quote on their information sheet for these pistons is "Important clearance information guidelines only, set clearance at o.oo3 thou". Although they do also state they have run them at 0.0025 thou clearance without problem.

Hi Mark

Good to know your running at 0.002 thou clearance without any issue. While that Ok for you or me to play around with and accept responsibility for should things go wrong.

If sell a barrel to anyone using these make of pistons, then I need to set the clearance at the manufactures stated clearance, unless the buyer requests a tighter clearance. Then they accept responsibility for any possible issues.

regards

John

I emailed the guy at JE when I first ran these pistons a few years ago asking him about use in a nicasil plated alloy block(B44 has a liner) and he recommended not going tighter than .002". So this time I'm experimenting with .002" and just thought it might be interesting info for you. I need to do more miles and run it a bit harder to be sure it's ok, but I expect it is. You will probably have people race with your cylinders and get feed back on things like that.

Hi Mark

That's good information, as I was only going with what was on the sheet they sent out with my pistons(same JE 80mm as yours). I should think you'll be Ok having got 150 miles in. At this time of the year your a little warmer than its ever going to get in the UK, but as you say you need to give it a hard run to be sure.
But good to know for anyone racing, that they can probably go down to 0.002 thou clearance with these pistons.

regards

John

Will the JE pistons have the modern very narrow rings or maybe the old type as on Hepolite?
I have been using JE pistons with narrow rings in my 80mm bore Laverda triple and I amongst others found the oil consumption to be too much.Dealers reports the same and blame the rings (The spring behind the oil ring broke on some also). I now use Ross pistons with old type rings and the oil consumption is very much lower. The Ross pistons is, by the way,a bit heavier than the JE..so JE`s with old type rings would maybe be better?

I believe the JE pistons with current narrow rings would work very well with Mark's nikasil bores, not so well with older iron cylinders, where softer iron rings would be better.
It was a common problems for Triumph / BSA triples when they arrived with 3 piece steel piston rings.

Adam. I'm using JE pistons with total seal rings in my iron barrel at 060".

If they are bedded in using a good oil ( running in oil makes a big difference) and not disturbed on the rings or hone they seal quite quickly and nicely.

John, you are unite right about the quoting of the 003", I could be too sure from memory but I knew it was less than stock.

On the TS rings, you can run tighter ring gaps according to the literature, I won't quote any figures.

However with my honed barrel have slightly more clearance than a freshly bored one, the ring gaps didn't require any filing etc to get them right.

Hi

I've just ordered another batch, witch should be ready for delivery end of March based on present schedules. At the moment I have four of the second batch with no names against them.

The earlier photo's shows a 79mm bore version (not yet Nikasil coated), but can be bored to suit your requirements as with the stroke. The original weighed in at 9.3kg, this one is 3.5kg.
It comes complete with a set of 12.9 grade bolt and studs which are 3/8 UNF top thread.

The price is 700 GBP plus P/P (no VAT), half the price when ordering and the rest prior to delivery.

regards

John

contact me on [email protected] for further information.

Hi Nick

Not sure why you would want to go with steel liners, which are going to mean the liners are either thin to get them inside the stud pattern, or really thick and you use the top flange to tap the stud pattern into! Plus you end-up requiring greater piston/liner clearance than with the Nikasil.

As I've had question about distortion before and ran tests to check this. Assuming the worst case between bore and stud clearance, which is the two rear out board studs. We set-up the test pieces with 3/8 UNC 16TPI drilled and tapped holes to represent the clearance between thread OD and 80mm bore clearance which is approximately 0.05mm between the thread OD and what would be the bore. Our test piece on the above clearance had six bored and tapped hole, with the test bolts torqued down to 25 ft lbs.

Test results gave a material displacement of between 0.0003 and 0.0005 thousands of an inch. Although when I talked to the engineer at the Nikasil coater, he said that in 30 years he's not had issues with distortion using the same material.

My barrel uses 5/16" UNC threads into the barrel on the big bore versions, as I feel this gives a greater head gasket sealing area between the bore and stud pattern.

Hope the above information is helpful.

John

Hi Nick

Yes, years ago I had a friend with a set of ARE barrels, head bolts used to come loose, UNF threads in alloy is not a good idea. Once we re-tapped them with a Whitworth thread (think it was the only one that would fit, no more problems after that.

If you can get 85+ BHP out of a A65, you should appreciate the benefits of not only dropping 6kg of engine weight, but also the better cooling and tighter piston/bore clearance.

Times have moved on and Nikasil and the other variations of the process have now been used successfully for years.

Regards

John

I tried thin iron liners in the first alloy cyl I made, they were straight and stopped from moving down by butting against a lip at the bottom, one of them turned a bit and cracked, the nicasil cyl I run now seals better and being all one piece is stronger, I think it's a much better solution for big bores.

Hi

I have two barrels in the second batch without names against them if anyone is interested, then drop me an e-mail [email protected]

regards

John

Hi

Only one barrel left on the second batch without a name against it. If anyone is interested, then drop me an e-mail [email protected]

regards

John

You still have my name against one John? I am expecting the pistons very soon.

Many thanks

Hi Allan

Yes one has your name against it. I'll send you an e-mail.

regards

John

Hi

I now have two barrels of the second batch available, due to a lad dropping out at the last minute.

Should anyone be interested drop me an e-mail [email protected] for information or details.

regards

John

email on the way with lots of questions...

Hi

Back to one barrel available in the second batch.

FYI

If your looking for a big bore street bike, you can use B40 pistons which means you can keep the standard pushrods.
Where using the shorter B44 piston means you need a set of shorter pushrods to go with the shorter barrel height.

My contact address is [email protected]

regards

John

Hi

Been a while since I made an update. My 650 test bike has now done close on 500 miles without any problems.
As it only had 5/16" base studs and I didn't want to completely strip the motor to change them out to 3/8" studs for the big bore version, I had one done to 75mm bore to replace the standard barrel.

http://s1314.photobucket.com/user/ecosse_lynx/media/A65_zps771f1ddb.jpg.html

E-mail me on [email protected] if you want any further information. I'll try and post a couple of photo's later.

regards

John

Hi

Eventually managed to get a photo of the test bike up yesterday. I'm waiting on delivery of another batch of castings, if your interested or want further information and details. E-mail me at [email protected]

regards

John

John,

Good sources of B40 pistons are hard to find. Do you know of a good source for B40 pistons? Also there seem to be more of the lower compression B40 pistons around then the slightly sportier 8.7:1 ones. I'd hate to lock myself into the taller barrel and be dependent on the lousy B40 piston supply out there. Excellent B44 pistons however are readily available. Along with Ed V I am also selling the real nice JE forged pistons for B44s that can be used with closer tolerances.

Peter

Hi Peter

I don't deal in pistons due to the wide variation in cost and quality. I bought a set from Ed V for my project bike.

My post was to let people be aware that they can use B40 pistons to get the big bore using their original pushrods. While using the B44 pistons requires shorter pushrods.

regards

John

Hi

While I still see that a large number of people are looking at the thread, don't you have any questions to ask! I'll tell you (learned years ago that I'm not a salesman) best to ask before buying them than after! If I didn't have a day job I couldn't afford to produce them, sure go work it out I don't mind.
At present I have 11 semi-machined barrels in stock, depending on order supply I can probably get them to you by end of April, depending on when you order.

regards

John

It is very easy to pull an end off and shorten the std pushrods. Nice looking pistons Peter.

Hi Mark

Yeah, it is for you and me and to know by how much. Not everyone has our skills.
All I was pointing out and was letting people know was the simplest and cheapest way to obtain a big bore A65.

I've been following your smaller porting thread with interest. I bought a small port head a couple of years back with a view to doing something with. However I've not even got that engine up and running yet, hopefully in the next couple of months.

John

Hi

It's three weeks ago since I've had a look at the thread. That must be about 1500 hits in the last three weeks and still people keep looking at it, but no one asks any questions!

If you want further information, contact me by e-mail [email protected] or call +44 (0)7802 500325

regards

John

Hi

350 hits since Friday and not one question! I decided to strip the barrel off the test bike, with just under 1000 miles. You can see the photos of the barrel and pistons on the link below.

Bores of the barrel are fine, pistons have some thrust marks as you'd expect. Perhaps this will lead to a few questions! If you do have a question call 07802500325 or e-mail me [email protected]

Happy viewing

http://s1314.photobucket.com/user/ecosse_lynx/library/?sort=3&page=1

John

Hello viewers, I nipped over to see John at the weekend and picked up my 750 barrels, it was a pleasure to meet John in person on a dry bright day back in my old school town.
Watch the projects page over the next few weeks, I shall be fitting the lovely new alloy barrels to my 71 A65 L, replacing the tired old iron barrels which are close to the end of their service life.
Cheers
GE

Hi Nick

Sorry I can't give you any details on crank balance factors for various configurations. I only manufacture the barrels and of the 20 barrels made so far, only one barrel has been made to suit the B40 piston. I don't built the engines, other than my own. The lad only picked up his barrel last Friday and doubt if its up and running yet. I believe the lad was having some of his engine work done at SRM but don't know the details of what was being done.

Regards

John

Hi Nick

The photo's I posted are of my test bike, which is just a 650cc. In order to get a barrel on test the only bike I had going was my 650 spitfire, so I made a barrel to suit and just swapped the barrel to get one under test.

The B40 piston has the same gudgon pin center to land height as the standard 650. It just means if you wanted a big bore road bike, and it saves having to change to the shorter pushrods.
I think Les Mason went with the B44 piston for the original Devimead design, as you could get competition pistons for the B44 at the time.

I know the first race engine I bought from him in 72 had nice Omega slipper pistons in it.

regards

John

Hi Nick

Yes, the Omega were a nice piston and as you say unfortunately no longer obtainable. If you want a good piston that can take a bit of thrash, then the JE is the way to go, I have supplied 7 barrels to suit these. One set is for a project engine I'm building, once I get all the bits together and start assembly I'll post a few photo's.

regards

John

best of scotland, lucky me

lucky me

produced with care, well finished and worth the purchase
regards A

:bigt

Hi all, my first post on this forum

I really want to have that cylinder barrel one day.
My old barrel is somewhat corroded so the fins are partly thin.
Is it 725 cc displacement with 79 mm pistons then ?
Does anyone have a link to the JE piston, and what compression do they have ?

I have a -69 Lightning with an SRM built engine, but the crankcase is from a -62 so I guess it has the 5/16" base studs.
What modifications must be done to the engine and carburation to make the new barrel work, if any ?
Is it a bolt-on or does the engine have to be rebuilt or balanced in any way ?
Is it easier to use OEM size piston sizes instead of a bigger bore ?

Note the very early engine number:
AND the crack on the corner...

E&V Engineering, a Forum sponsor has JE pistons

http://www.shopevengineering.com/

Gordo

Hi

Gordo has supplied the like to Ed V for you.

I have a question for you, from the photo your barrel looks to be the original 650 (75mm bore) BSA barrel!
I don't recommend running big bore kits with 5/16" base studs. You can have the crank case bored and tapped to take the later 3/8" UNC x UNF base studs (give you a chance to have the crack welded up as well). You don't need to change the stud spacing as the barrel can be fitted to either early or later stud spacing.

The barrel can be supplied up to a bore of up to 80mm and the height adjusted to the most common stroke changes. The 79mm bore with the standard 74mm crank will give you 725cc while the 80mm bore will give you 744cc.

If you have any further questions feel free to ask or you can e-mail me on [email protected]

regards

John

Hi John, I don't know if you have looked into this but the alloy cyl will have a different expansion rate to cast iron and will effect tappet settings. On my bike I also run C/molly pushrods which makes it even more the reverse of the standard. I need to set tappets at zero clearance cold for best results. With stock alloy pushrods it may be best with somewhere in between.

Hi Mark

When I first built-up the test bike I just set the tappets to normal (standard push rods), then notice they were a bit noisy. After I had the barrel and piston off about a month ago for a look see, I set them at 0.008 & 0.006 thou and its better. From the sounds of it I can come done a few more thou.

Thanks for the tip Mark.

On a different matter. Yesterday I had an e-mail enquiry from Kennie with the following e-mail address: [email protected]
I did reply, but got it returned as a none delivery. If your reading the post please get back to me.

regards

John

I wonder what the clearance when hot would be Mark??

Did this also give you the best performance??

Thanks John!

Regarding 80 mm JE pistons, I guess they are custom order pistons ?

What about the CR (compression rate) ?
The 75 mm JE pistons come in 9.2 and 10.5 and I guess for some reason I want around 9.2 as it's close to the Lightning spec.
Or do I want more power ? (and possible problems?). I guess the ignition timing would be different ?
But increased bore gives higher CR. Is this compensated for when they design/make the pistons ?

Will the carbs work fine for 744 cc ?
And the OEM head gasket ?

And finally, is it worth the bigger bore without any head work ?

Sorry for asking a lot

Hi

I'll try and answer your questions.

I believe Ed V normally has a stock of either 80mm B44 or 75mm A65 pistons, but you would need to contact Ed just to confirm he had what you require.

I would think for the fuels available and road use the 9.2:1 CR would be high enough.

The ignition timing would remain the same, or may respond better to a small change depending on the fuel and CR.

The bore size doesn't impact the CR and simple way to adjust the CR is install a slightly thinner or thicker head gaskets as required.

The big bore would benefit from using larger valves, while 30mm carbs would work unless your to be running at high RPM a lot of the time.

My own test bike and another barrel supplied are 75mm bore because the engine base studs were 5/16", your still going to be 6kg lighter. I can do you a barrel to suit, which would save you changing the base studs, although I'd recommend you fix the crack in the crankcase. These barrels use 3/8" HT head bolts/studs and standard head gaskets.

Hope this is of help.

John.

Thanks!

It will anyway be a winter project so I could as well change the base studs when spending time and money on the bike.

I always believed that bigger bore made higher CR as the cylinder volume that will be compressed is higher, relative to the combustion chamber in the head which still has the same volume as the smaller bore engine.
Of course the piston shape also matters for the CR as few pistons have a flat top.

Anyway E&V has 76,5 mm A65 pistons with 9.2:1 CR, giving 671cc, if I am correct ?
I guess that is the easy way, not dealing with any unknown factors. And keeping the 5/16 base studs.

Hi

If its to be a winter project, then changing the base studs and going for the big bore would be the logical way to go, as you get the extra cc.

Once you figure out which way you want to go, or if you have any other question you can contact me direct by e-mail on [email protected] or my mobile number is +44 (0)7082 500325.

regards

John

This post has gone a bit quiet so I'll wake it up with a heartfelt thanks to John Hill. I've bought a set of barrels from him and from the initial inquiry and tech questions/advice through to delivery the bloke was first class.
The bloke even refunded a few quid I overpaid on postage - so he's obviously not in it to pull money off you.
I bought the ED V 80mm pistons, off the shelf, and John prepped the barrels to suit, fitted perfect.
The quality of the barrels, casting / machine work, is first class and when you compare them weight wise with a standard set the weight saving is major.
These barrels are for a back seat project and won't be seeing action for at least 6 months but I'm already looking forward to it.
Quality opportunities like this are few and far between for our old bikes and so I would urge all you A65/A50 boys who fancy a big bore / weight saving upgrade, plus with a variety of personal specs available and a very reasonable cost, to get in there while you've got the option. These won't be around forever and in a few years you'll be paying through the nose for these, if you can find any.

I guess 80 mm pistons are 79 mm + 0.40 oversize ?

Here is a JP Australia B44 high compression piston http://www.classic-motorcycles.co.uk/cgi-bin/ecom.cgi?Command=ShowProduct&db_pid=5600

And here is a JP Australia B40 high compression piston http://www.classic-motorcycles.co.uk/cgi-bin/ecom.cgi?Command=ShowProduct&db_pid=4266

Can any of these be used ?
(Never mind the pictures, they are not of the actual piston.
They probably look like this



Someone was not happy with JP Pistons http://www.b50.org/phpBB2/viewtopic.php?f=3&t=3439