Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Nourish A65 Motor

Gavin,

In your shoes, I would grind about 0.100" off the length of the wrist pins (or use the shorter C15/B25 wrist pins) and make a stepped bushing to go over the ends of the wrist pin that is a tight fit. on both the wrist pin and in the piston.

I'll see if I can knock out a drawing later if that doesn't make sense.

I just saw the note about your worries concerning rear hub strength. I say this with a grain of salt and hope I'm not cursing myself but, I have been running the QD hub on my LSR raceer for 5 years and that hub is hangin in there ok. We are putting over 100 hp to the ground so your set up should be ok. Cheers, PRT

Similar to the cups on a u-joint, except no rollers, just a tight friction fit.
The walls are going to be pretty thin though, about .030" unless the diameter of the pin is reduced.

Another option would be to get a new set of rods made up to the proper specs. Selling the Carillo's should recoup a good portion of the cost.

What sort of ignition system are you going to run on the 90 degree set up ?

So I'm guessing the rods have a bushed L/end, what is the o.d. of the bush? If removing the bush makes it close to BSA pin size maybe the rods could be machined exact and you could get pins with DLC and run with no bush. Other than that custom pistons with Norton size pins, an advantage of this is you could specify less dome, when the swept volume gets bigger and the chamber volume above the piston stays the same, comp ratio goes up, if that dome in with a 84mm-85mm stroke gives 10.5 - 1 a 90mm stroke will give more, you can run them lower in the block for less comp but if I was getting them made custom I'd reduce the dome. Either way emailing Ed V I think would be a good idea. I wonder if that means the big ends are Norton size, if it does its a good thing to have the extra dia and strength in the crank.

Thanks for the input on this from forum members. Update: I have bought some new SRM Plasma hardened valves, and they are being fitted at the machine shop, the inlets being their 43.5mm Dia. I have removed the rods, Thanks for the reassurance PRT, I was thinking of sidecar requirements. I'm glad I've got the E&V pistons, not least because of the quality of the rings. Correctly measured, the rods are in fact 6" long. Can't accurately measure the little end 'till I push the bush out. In answer to bon, I spoke to http://www.electrexworld.co.uk and http://www.kirbyrowbotham.com, who said they could supply a kit much like the usual Boyer type for £225. This would fire like a Ducati and fit in the points housing of a BSA. Now the rods are off, it would be interesting to see what you mean Alex, by a stepped bushing. Can't do anything 'till Monday, so I'm open to all suggestions.

Kind Regards

The outside dia. of the small end bushing is probably ca. 20mm. To ream that ouy to 21 - 22mm would not weaken the conrod too much and then make a bush of chrome moly steel with inside dia.19mm (std a65). I have sucessfully made such thin wall steel bushings for the worn out small end on several Honda twins (Black bombers) which have the gudgeon pin running directely in their c.moly conrods.

Regards

Gavin, with ignition it's preferable with the odd angles to fire the plugs individually. Pazon are working on an 'Altair ign' for singles, that only fire the plug when needed, with no idle spark, when they get the kits done I'm hoping to get two and use a modified ign plate to fire both individually. I'm using a Honda VT250 ign at the moment that is individual but it has excessive adv, the long stroke motor seems best with around 28deg only. So to get that its a bit retarded down low with an advance that doesn't even start till 2,000RPM.

Well I have been busy recently. Have just got back from Coltec Racing, in Hollesley, Suffolk. They are what's left of Holbay racing, anyone remember them? Richard, said he could make a new bush that would work ok with the Carrillos and E&V pistons, so I am very relieved to hear that. I also took the crank, and upon inspection, it needs a regrind and a good clean as it's had a hard time from the po. The only people he knows of able to do the job are in Coventry and I shall drive it there, unless anyone knows different. He has a production quality grinder, but it's out of commision at the mo. An ordinary grinder "Won't do", as they are only good enough for regrinds and not suitable for a crank like mine. His words, not mine. Now off to see how the head's getting on. Ttfn.

Hello Gavin

What bore did u choose for the nicasil, alu sylinder ? How much longer than stock is the cylinder from Traupel ?

im assembling a A65 engine now.
I use big bore cylinder in cast iron from SRM that is 8mm shorter than stock A65 cylinder. It forced me to make very very short conrods on 157 mm. I have a Norton 89 mm stroke crank, Ed V 80mm pistons. From Bsa B44. I'm worried about the flexing of the crank and the short conrods. My crank is stock 360 degrees. I Consider the alu cylinder to, but as I understood from Traupel, the limit of bore is 77mm

Andreas

Hi Oleandreas, I have only spoken to H. Traupel twice, but I've now agreed with him to make a set with 77mm bore. This will fit my +.080 A70 pistons from E&V. Stroke is 90mm, with standard length rods. The overall height of the standard motor from the cankpin to the piston crown base is 37+152+30, mine is 45+152+30. given the first figure is half the stroke, the other two constant, as the rod length and pin centre to crown base. Therefore, 8mm over standard height barells. The exhaust was a standard size. The head's not ready yet.



Kind Regards

Just some more information, for a more straightforward job, you can use a Norton crank, (89mm stroke), Triumph rods, and T140 pistons, then remove 1mm from standard height barells. This makes a revvier motor I guess.

Kind Regards

Hi Gavin,

Your numbers seem slightly off.

According to Ed V, "The standard A65 compression hgt is 1.415" at least on our pistons". 1.415" = 35.941mm.

For a standard A65...
Stroke = 74mm
Rod Length = 6" = 152.4mm
Compression Height = 35.941mm
This suggests that block height is 225.341mm as that is where the piston deck will be at TDC.

Again, according to Ed V, "A70 compression hgt is 1.218"...", in reference to the same pistons you have.
1.218" = 30.9372mm.

For your A65 motor...
Stroke = 90mm
Rod Length = 6" = 152.4mm
Compression Height = 30.9372mm
This suggests that your piston deck will be 228.3372mm from the center of the crank at TDC.

That works out to 2.9962mm more than standard, call it 3mm. Your custom cylinders should probably be 3mm taller than a standard set of A65 cylinders.

If I'm off base here, please show me where so that I can correct this chart.

Given a 3mm taller than standard cylinder, it looks to me that your compression ratio will work out close to 10.3:1 with a 1.5mm head gasket.

Hi, from what you have written, TA, one would assume that I have incorrectly measured standard piston compression height. However, I can assure you that I measured genuine BSA A50 pistons from the pin dia. to the crown base/deck and they are 30mm give or take a decimal. Yes, E&V pistons are 30mm also. Therefore the only difference in the "Crank to crown" height comes from the different stroke, i.e. 90mm instead of 74mm. This means 45 instead of 37 in terms of the throw, yes? A difference of 8mm... As I understand, A50 AND A65 barells, although recognisable by the different amount of fins, are in fact the same height. This is how I have done my calculations. I am ok to take a hit on this if anyone knows different, measure a genuine BSA piston for yourself...

There's the issue right there, A50 and A65 cylinders are not the same height, nor are their pushrods the same length either.
The fact that the A50 pistons you are measuring have a compression height of approx. 30mm shouldn't really have any bearing on the cylinders you are having made, I would be very surprised if Rainer's cylinders weren't based on A65 height rather than A50.

Ed V was very specific in his response to my questions regarding compression heights of the pistons he sells, you should certainly be able to trust his figures.
Scepticism of my calculations probably isn't really a bad thing though!

Ok, as I said in my previous post, my only experience is with my A50. I do know however that pushrod lengths are different for A50 and A65. I too have spoken to Gary at SRM, and he said cylinder heights are the same; or is something lost in translation? Do you have a set of both please to compare?

No easy access to the pistons at present.

The cylinders though measure approx. 5mm difference in height with the A50 shorter than the A65. 3.7" and 3.9" approx.

1969 Royal Star and 1967 Lightning, in my workshop, five minutes ago.

Perhaps Gary meant that the height of the SRM Big Bore barrels is about the same as the A50. A65 cylinder height is the same as A70 cylinder height.

You are comparing an A50 piston with a 74mm stroke to an A70 piston with 85mm stroke. You used a 74mm stroke for the A70 which is also throwing your calculation off by 5.5mm.

According to Ed V, the compression height of the A65 pistons he sells is 0.197" more than the A70 pistons he sells. This works out to 5.0038mm.
It all points to the A50 cylinder being approx. 5mm shorter than the A65/A70 cylinder.

No it's 4speed with an extra cog sitting on the shaft, I was watching as well and asked.
I have read of people using A70 pistons in a short block to pass it off as a 500.

Ok, its not nice having your parade rained on, but thanks to forum members, I'm going to have to phone Rainer again and ask him nicely, as I've already stumped up 600Euros deposit, if he wouldn't mind making them 3mm taller than standard, yes?

3mm should be good, based on the info you've provided.

One thing still concerns me though. Your con rods, make absolutely sure that they really are 6". The Norton size little end makes me wonder if the rods themselves aren't Norton length as well. If they are, they are 3.175mm (1/8th") short of 6" and the barrel you are having made would need to be the same height as a stock A65 barrel!

No rain, just sunshine!

Hi Two Alpha, Yes they really are 6" measured with my steel rule. It's comforting to know that others reading this thread are learning something as well, maybe. (Or maybe not). I don't mind admitting when I've got something wrong, and clearly I did in this case. I'm grateful as I said to Forum members, for giving me advice. After all, that's what a forum is for, n'est pas? Rainers ok about the height issue, BTW, the casting is big enough to accomodate the tall height anyway, only when the machining takes place, does he need to know exactly.

BTW, try finding anybody who can do this for you in the UK, as professionally as Rainer. I doubt you can, but then again, that's what makes Britain "Great", isn't it? I'm not such a tenderfoot as to realise the economics of it all either. I can't bring myself to use a silly icon, so I won't then.

Kind Regards

I'm a European, believe me. I'm too old for all this anti "We will be putting our country's interests first" mularkey. A century of war has brought us back to the caveman mentality. I believe we should look to the future as part of the European project. Union is strength, we couldn't punch our way out of a paper bag on our own. No more politics please, this is my thread. (Or I won't play anymore)

Kind Regards

Been a while since my last update, and I need some advice please. Ok, so the A70 pistons now fit the rods after some reaming and scraping of the small end bushes, and I have got the cylinder head back fitted with new big valves. I should pick the 90 Deg. crank up today after a - .010 big end grind. I've also had a nickel weld repair on the pinion keyway, and of course the compulsory oilway clean.

My next issue is with ignition. The motor came with a Lucas Rita box and a special reluctor made for SRM by Mistral Engineering back in '98. Mistral tell me it would have about 34 deg advance, and I'm OK to try to set this up, but having spoken to SRM about it, am told the max advance I need is 28 - 30 Deg. because of the long stroke. I am concerned then, that it would be difficult to start, because of a retarded state at cranking speed. Do I need a different box? Is there an alternative method? Can I run lights or do I have to settle for daytime running only?

I'd be setting it about 28deg total, I'm sure the Rita will work fine. I have used one. I'd guess you would still have 5deg advance when kicking. I'm using a Honda VTR250 ign at the moment and it's less suitable, probably idling at 0degs or even after TDC, and it doesn't advance at all till 2,000RPM, but it's fine when running and will idle ok, but is a bit hard to kick start, though bump starting is instant, this may be due to something other than ign timing though. At least when I use the kicker its less prone to try taking my leg off. I don't think more than about 5deg advance would be very wise when kicking these long stroke motors.
Andy at Pazon said they are in the process of doing some altair ignitions for singles, I'd like to run a pair when he gets them done, with idle stabalization as well as one spark only when needed, no idle sparks.
If you look in this link under 'features' it shows the altair ign curves for twins.
http://www.Pazon.com/ignition-system/altair-twin

I can't see any reason why you'd need less than 15 degrees advance at idle,with no further advance until about 1500 rpm.Real men can start real bikes locked on 35 degrees full advance (without breaking a leg),and they start OK and idle well;but you can't lug the engine below about 3500 rpm.Also,if you open the throttle too much when starting,you can break a leg or an ankle.
If there is no further advance between cranking speed and just above idle speed,you get a stable idle.

Maybe the long stroke requires less advance because you don't need such a high piston dome for a given compression ratio.5 degrees retarded is a lot for just having less piston dome for the flame to travel around.The flame must also travel further now,to get across the bigger cylinder bore.
31 or 32 degrees full advance could be about right.If you have say 12 degrees at idle and 32 degrees full advance,that means 20 degrees advance built into the ignition system (not 34 degrees).

If you need to turn it back to 28 degrees full advance,you'd still have 8 degrees at idle.
8 degrees at idle is less than ideal,and the engine will run hotter when you're idling in traffic,as compared to 12 or even 20 degrees.

Just my thoughts.Most electronic ignition advance curves are not quite ideal.