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.
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've used the B44 pistons and they were fine. The problem I had was with the 89mmstroke crank I use and where the piston skirt is. The skirt was coming out the bottom of the cyl and not being supported properly, ended up cracking a liner I was using then. I now use Ed V forged B44 pistons which are shorter and have the skirt higher staying in the bore at BDC and are higher spec as is the ring pack and in my opinion represent excellent value. Anyone building a long stroke motor needs to be aware.
I'm just bumping this thread hoping to get enough interest for John to make another batch of cylinders (so I can buy another.) I bought one with an 80mm bore. I've not use it yet as I'm waiting for my bush conversion to be completed.
These cylinders are art. Every few days I get mine out & just admire it.
Ray Elliott --- A65, A70, A75, T120, T140, T150, T160
While I have never come across a JP piston before, but from some of the earlier link comments it doesn't sound like I should be in a rush to either.
Please ensure that your not getting mixed-up with JP pistons and the JE pistons which Ed V sells, they are NOT the same, as Allan said the JP pistons are CAST while the JE pistons are FORGED and high quality. The JE pistons I do know and are very good.
In answer to Allan's question. You can use a B40 piston to obtain a big bore A65, if you were just looking to use it in a road bike where your not going to be giving it a hard time. This is something I've explained earlier in this thread. Should anyone want information on the various configurations that the Alloy barrel can be made to suit, drop me an e-mail at firstname.lastname@example.org or call me on +44 7802 500325.
I've had a note from Ed V that he has received his first batch of JE B40 80mm pistons. Thus giving you the option of running a high quality forged piston.
At present I have a batch of 10 barrel castings ready for machining, to date I have names against three. If your looking to shed 6kg from your engine, increase the capacity and get a tighter piston to bore clearance either e-mail me email@example.com or call me on 07802 500325 for further information.
I shall be machining a batch of 10 barrel castings towards the end of next week, to date I have names against six. These will be big bore, so if your looking to shed 6kg from your engine, increase the capacity and get a tighter piston to bore clearance, then there are four up for grabs.
These should be available for delivery in one Month. What I'd need to know is the stroke if not standard and I will require a piston prior to sending for Nikasil coating. To order either e-mail me firstname.lastname@example.org or call me on 07802 500325 for further information.
A very interesting and tempting thread John. Beautiful workmanship. I'm simply amazed at what's available for all the British bikes these days. I've only just bought a MK II Spitfire that won't be in Australia until November or December. And before I look at big bore barrels, I'd have to do the needle roller conversion. But then it begs the question of what crank to use and all the possibilities that your barrels then add to the equation. It's too soon for me to get really serious, but just wanted to let you know it's something I'd be very interested in once I've seen what I've bought. Cheers John
Current: 2 x 1966 A65S, 1 x 1967 A65SA, 1 x 69/70? A65LA space Y, 1 X D14/4 & 1 x B175 Past: 4 x 1976 T160V, 1 74/5 T150V, 83 model GSX 750 ESD, Z650, Katana 1100(Bathurst Model), 79 T140V, 70's TR6, 2 x 1971 BSA 250 Gold Stars, 50's 350 Goldie, A65 Spitfire semi basket case, 1965/6? A65 LC, Tiger 21 350 & a D14/4 Bantam, 175 Bridgestone Twin with Zimmerman discs!
As were now into mid September and people are starting to think of winter re-builds. Increase the cc's and reduce the engine weight by 6kg. If there is enough interest in my alloy barrel I can have another batch cast up.
e-mail me on email@example.com or call 07802 500325 for further information or if you have any questions.
Well in 15 days since my last post here and there have been 1001 hits. So looks like a few of you are maybe thinking about it! Although the only call I had since the last post, was a guy looking for an A10 barrel.
Anyway, I'm not go and cast another batch of barrels, based only on people looking at the post. If people with a serious interest get in touch either by an e-mail, call (details above) or post/PM on here, then we'll see if we can still get a batch cast, machined and coated before the Christmas holiday period. In time for a winter re-build.
Look what I got for christmas. 20 new castings ready for the machine shop in January. Give your A65 a new year diet and shed 6kg, anyone interested then drop me an e-mail at firstname.lastname@example.org or call me on 07802 500325.
In answer to your questions. The clutch was an old Suzuki GT750 I had laying around and modified it to go with an alloy chain wheel, 2kg lighter than the standard set-up and doesn't wobble around when disengaged. Just a little engineering exercise to see if it would work.
The generator is actually a lighting and self generating ignition system which I got from Electrex World.
Sorry I don't it was just for my test bike and works well, but if you give Peter a call at Electrex he'll be able to tell you. You could go for a Power-arc ignition system then you can play with it yourself on the lap-top.
Personally I never fancied hanging a mag way out there on a solo (maybe not so bad on an outfit). Years ago I did actually dummy-up a K2F at the back engine, using a cut down old mag carrier from a blown Triumph casing welded to the inner timing cover and was using a toothed belt for drive. Also in the 70's a lad used to race an A65 with a mag mounted above the front engine mounting with a chain drive.
Unfortunately while replacing the clutch centre with the four spring version and adding an alloy pressure plate c/w thrust bearing should improve thing a little. It will not correct the inherant design issues.
The springs pressure is the only thing that keeps it all running together inline, pull in the clutch leaver and chain wheel wants to wobble around, the chain wheel running on a small width rollers which are offset to the chain wheel centre line is another disadvantage.
The clutch does work when set-up correctly, that's as much as I'm going to talk it up.