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

Hi everyone,
I have just bought a 1969 A65 bottom half. It has an SRM end feed conversion, running into a 90 Deg. NRE crank. Yesterday, I phoned Mr Nourish and he told me from the number stamped, that it was balanced to Carillo rods. It still has them. They are 6" and the crank throw is 90mm. I also have a standard top end ready to use from another motor. My question is Do I have to use a custom cylinder/piston/head arrangment? Can I use a standard A50/A50 top end and see what it feels like? Anybody done this? Needless to say, i have split the cases, and upon inspection, all seems in very fine fettle and ready to use.

Kind Regards and a VERY Happy New Year to all!!

Make sure that you have a camshaft that matches the new timing of the crank. The cam timing of one side will have to shifted to the 90d. A65 pistons will collide with the edges of the A50 combustion chamber. Either the pistons or the head needs to be modified for clearance.

If mine, I would use a standard A65 head & work out any problems with the 90d setup first, like how to fire the cylinders at the correct time. Cheers, Don.

Sorry I forgot to mention, it was put together by SRM using a special 90 Deg. cam which is also included. I also have a Lucas Rita ignition supplied by them for it. It was originally done in 1998.

Kind Regards and a VERY Happy New Year to all!

Congratulations on your purchase.

Mark Parker will certainly know which pistons you will need, can't imagine him not joining this conversation as soon as he spots it. Not sure how early he hits the computer on New Years Day though. I think it's just after 5:00am where he is.

Another person who would know would be Ed at...
E&V Engineering

They're a sponsor here and word has it that the pistons they supply are absolutely deluxe.

Hi.
In my a65 bore & stroke 77 x 85 (Nourish crank) I use modified Triumph T140 pistons (the valve pockets needs grinding because of different angles). A65 pistons cannot be used. Std a65 cylinders can be bored out to 77mm without any risk. I used std cylinders 77mm for a couple of years before buying alu.cylinders with nicasil (also 77mm) from Rainer Traupel in Germany.
If you can find T140 high comp.pistons there will be more material to deal with.I found TRW h.comp.pistons on e-bay.
The a65 cyl.head will not need any modifying.

Regards

Nice, any pictures? If you intend to use stock pistons then the barrel has to be taller for the longer stroke. I do not know off hand if the wrist (gudgeon) pin can be moved high enough in a special piston to keep the stock barrel. Taller cylinder also requires longer pushrods. You still need to clay the pistons and check for valve interference in any case.

Here's the picture that was on ebay. The GC serial number puts it off the line in June, 1969.

Ed V has forged A70 pistons that would be ideal, A70s have 85mm stroke and a higher pin height in the piston to suit. His pistons and ring packs are very good, I use his B44 pistons in a big bore cyl. If they are a little more expensive than cast, its because they are better quality and worth it, actually you probably wouldn't find A70 cast pistons anyway. T140 pistons are OK but the valve cut outs are for a Triumph and need re-doing, so its probably cheaper getting the A70.
The crank is ballanced to the rods, but did he say anything about piston weight? Close probably would be OK so long as they were the same, it would just vary the factor a little.
Anyway looks like you got some good bits, hope you keep us updated on the build and how it goes.

My only experience is with my A50 Cyclone motor. I'm really not bothered about cubes, as long as it's "Sweet". With this in mind, I would like to be able to construct another A50; but, being a realist, acknowledge that this probably isn't going to run at all well, probably not possible at all. So, I think I'm looking at a big bore kit, though SRM closed until the 3.1.12, can't talk to them yet.

This was the idea of posting, just to gather some options. I'm grateful for the info so far, and yes, the photo previously posted is of my motor. BTW, not pictured are the clutches, gears and other sprockets included. The idea of a 90 deg. engine is the primary motivation for this project, not a hot rod/street racer/thing.

I'm now off to bolt the cases back together and fit oil pump, gears, timing cover etc. I've taken the advice of a local 72 yr old "Legend" round here, and I shall not worry about balance 'till it's running. "See if you like it" -Sounds good to me. First though, is the small problem of finding a top end solution. Thanks again.

A VERY Happy New Year to all!

I don't think SRM are doing long stroke B/bore kits, these have the taller block, their 750kits for std 74mm stroke motors uses a B44 based piston with similar pin height to an A70-T140 and their block is shorter to suit. A70 pistons in a std 650 cyl with A65 head will give you 750cc and plenty of performance. And is probably a not too expensive option.
I wouldn't put an A50 top end on it, even if you did you would need special pistons, plus that cam is probably 'race' orientated and better in a bigger motor.
750cc would be a good size.
I'd recommend fitting 520Xring chain and sprockets while you're at it, and tall gearing.

A note about gearing, with a 90deg 750 B/bore std stroke, my brother runs 20-40 final gearing. He uses a different back wheel. If you are stuck with a BSA wheel and 47T sprocket go as big as you can on the front, I think there is a 22t in the photo, because the 90deg will pull better. This is the sort of sound you can expect:
http://www.youtube.com/watch?v=vBtY6y8rXls&feature=related

That sounds good Mark but I always felt that this clip was awesome.
http://www.youtube.com/watch?v=oBD2...wUtLg-Y8dA&index=15&feature=plcp
Amazing. Doesn't sound much like my A65!

Got home from work today and phoned SRM, spoke to Gary. Yes they dont have the larger kits at the mo, only the shorter length barrel kits. It looks as though I have a hot cam as well, so will be looking to change that to a spitfire profile. I need a barrels good enough for a 90mm stroke crank. I may have bitten off more than I can chew, yet I feel compelled to finish it. Dave Newman can reprofile the cam in the UK, so I will start there.

Kind Regards

Thanks Alan for taking the time to photograph the heads. At the moment, I'm not looking for another head just yet, as I want to explore the Barrel/Piston choices I have. I am lucky in that I have some very capable machinsts willing to help me out. Also, one of them is a sprint bike builder. Nothing scares him! The aluminium/nikasil option seems the way to go, so I will phone Rainer Traupel when possible.

Inlets I use are 44.5mm, exhausts are 39mm (cut down Jaguar, the exhaust valve head was also reduced in diameter) this is an old head, welded for more comp with T140 pistons, it was around 11-1, and a bit hard to start, a better ported open chambered head with the same valve sizes and less compression gave better power in midrange and top end.

This head had 36mm carbs, 38s worked plainly better. We have run a 90deg 650 with these valve sizes and 38mm flatslide carbs, I think it was similar to a std 650 down low but after 5,000 hit a fierce power band like a two stroke. This shows the ports, I now 'D' the port by filling the floor a bit which brings power in earlier without loosing anything later.

So is the crank 90mm stroke Gavin? I use 89mm with rods a little longer than Commando rods but shorter than 6" It takes a bit to squeeze everything in. You will probably need to open the crank case mouth a bit for an alloy block.

Hi Mark,
In answer to your question, the crank has 90MM stamped on it, but when I spoke to Mr Nourish, he said 84, but I think he was referring to the A10 dimensions? (He was trying to do some mental arithmetic out loud).On measuring the difference between BDC AND TDC, it's between 85-90. With steel rules, I'll measure across the crankcase mouth, to get an accurate figure. Spoke to Mr Traupel today, and he says he can make barrels according to my requirements. When we speak again in a week, I'll have the correct figure. Meantime, I think I'll get some A70 pistons from E&V.

Kind Regards

Hi Everyone,

Just an update. I now have a Devimead big bore head for it, c/o a Britbike member here, arrived in a timely fashion thankyou. Also on their way is a pair of E&V pistons, a sponsor here, and last but not least, I've got some aluminium/nicasil lined barrels on the way from Germany, c/o recommendations from members posts here. It makes sense really to have the aluminium barrels, as the heat from modern soup/"Fuel" makes our old motors suffer in their standard form one way or another.

Gavin, do you have specs on the 90deg cam? If I were you I'd use it as is and see how it went, big motors can tolerate bigger cams, it may run very sweet with it. Hope your bike has good brakes.

Brakes? Standard 1965 Single sided 8" front, standard 7" single sided rear on 42T Sprocket, QD hub. I'm more worried about the QD hub to be honest. The torque generated might destroy it.

Very interesting project you've got on the go there Gavin.

Bore to stroke ratio will be about the same as an A10, so it should be very sweet to ride once she's all sorted.

Yes John it is, that's what keeps me keen to see the results. 5MM or so over BSA Block height, means longer pushrods. My sprintbike builder friend makes his own pushrods. Using VW items, which are "Exceedingly" long, they are "Cut'n'shut" to provide the required length.

Kind Regards

Ok, run into a bit of a problem. I've collected the pistons from the Parcelforce depot today, and lovely as they are, they won't fit without some headscratching. These things are sent to try us! Of course the gudgeon pin dia. is. 750", but my conrod small end bush will only accept a .688" The conrods are Carillo forged steel, and I don't think I can just ream ream them out, as I don't think there's enough meat left. Can anyone suggest an engineering solution please?
Kind Regards

Gavin

Looks like the rods were probably made for Norton Commando pistons, according to Carillo page 40.

Perhaps there would be a machine shop solution by modifying/bushing a set of Norton wrist/gudgeon pins.

Ok, I have a C25 piston, and it seems that this is a perfect fit onto the rod.

Any progress Gavin?