I bought my first BSA in 1970. It was a C15 that a friend of my dad's was selling and was in bits. I paid £5 for it rode it on L plates, took my test on it and sold it for £15. After that I had a 1955 Royal Enfield 350 Bullet, a 1956 Triumph T100, a 1958 T120 Bonneville, which was the first bike I did a proper rebuild on and I spent a lot on the engine rebuild. I went on to own and ride a few Japanese sports bikes and a few modern Triumphs.
My current bike is a 1966 BSA A65 Lightning, which I bought in the mid 80's from a guy in Derby for £400. When I bought it, it was rideable but a bit of a mess. It had had a sidecar on it at some point and the frame was bent. The twin carb head had been replaced with a single carb head and the exhaust system was an aftermarket high rise system, similar to a Firebird. I spent about a year restoring the bike to it's original specification and as I had little experience of A65's and without the internet to help, I read a lot and employed the advice and services of SRM.
In the late 80's Steve McFarlane was still with them and I remember buying a brand new set of Devimead 650 cylinder barrels from him, which gave me nothing but grief for a long time. The start of that grief was when I first put the bike on the road. I had an oil leak which appeared to be coming through the cylinder barrel casting in the cam follower area. I contacted SRM and was passed on to Steve, who asked me to send them back and he would sort it out. At that time there was something going on at SRM and there seemed to be a clear divide between Steve and the rest of the crew. It was just before Steve parted company with SRM. Anyway I got the barrels back and once again tried to run the bike in. I kept getting the engine tightening up and at one point it locked the back wheel up on a sweeping right hander and resulted in a huge slide that I only just managed to recover from and luckily had a very wide grass verge to run off on. My experience riding speedway on my JAP 500 helped me out of that one, I'm sure. It could so easily have been disastrous.
All the time these 'partial seizures' were going on I was in contact with Steve McFarlane at SRM who insisted that the cause was 'my mixture must be too weak' and 'to get the carburation right'. I had fitted a twin carb head with pair of brand new Mk1 930 Concentrics on the bike and I was convinced I had them set up right, so after that near highside I stripped the barrels off and took them to a friend who worked for a local engineering company who were specialists in engine rebores and crank regrinds etc. He measured the bores on my barrels and there was just over a thou clearance on them, which was way too tight. I contacted SRM and was once again passed straight over to Steve McFarlane. I told him what I had found and he agreed to have a look at them. By now Steve had become more than aware that I was a qualified mechanical engineer, with a good amount of engine rebuilding knowledge on car and motorcycle engines. He confirmed the cylinder bore clearances were way too tight and honed them out. When they were returned to me I put everything back together and once again took the bike out on the road. Everything was fine after that and I went on to cover about 5000 miles trouble free. Once I had gained some confidence in the bike my first proper ride out on it was when I rode it from Hull to Knockhill, were a mate was racing his Norton in the Bob Mcintyre Classic. He had asked me to go along and be his mechanic for the weekend. The bike ran well, drew plenty of admirers and I entered it into a couple of shows, where it came away with trophies from both of them.
I am now currently in the process of doing a second full rebuild on the bike and putting a few things right that I wasn't completely happy with the first time round. I intend to fit the Devimead 750 kit that I bought from SRM in the early 90's and have sent my bottom end, con-rods and pistons to SRM for a complete overhaul and crankshaft dynamic balancing. They are also supplying me with one of their oil pump kits, a new camshaft, a new high strength Moly pushrod set (I have a set of new cam followers) and a new OPR valve. Along with all the seals, gaskets, con rod bolts etc. the total bottom end bill is going to be around 2K. On top of that I bought another cylinder head which SRM have overhauled, fitting new larger inlet valves and opening up the porting and gas flowing it to suit the 750 kit. That work cost me just over £700 but it means that I have the original 650 barrels, cylinder head and 30mm carbs. I was originally intending to fit Mikuni carbs and I rang SRM a while ago and spoke to Geoff Dewhurst. At the time they only had 30mm Mikunis in stock and I I asked him if they could get me a pair of 32mm Mikunis. His reply was 'why do you want to fit Mikuni's?' I replied that I was under the impression that SRM recommended them. He then went on to tell me that the new AMAL Premier Mk1 Concentrics were a better option. That was ok with me, as I like the Mk1 Concentrics. I personally think they are the best looking carb on the A65 engine and they fit well with the original air filters. I've never had a problem with setting them up and they have alway been reliable in my experience.
Allan G has offered me some good advice with his thoughts on what I should be doing with the engine and it has got me thinking about the ignition system and the camshaft.
I would appreciate the thoughts and experiences from other A65 owners on these subjects as I would like to fit the best ignition system and camshaft, Bearing in mind the amount of money I am piling into the engine, it would be daft to cut corners.
Some other things I would consider for the rebuild are as follows:- - are you using the original conrods or new ones? May be worthwhile installing billet rods or the later stronger OIF types. - what about the timing side journal? Presumably SRM are installing a new one and line boring it together with shimming. The original setup is usually fine if you have an oil filter fitted but some prefer the upgrade to end feed oil supply and roller bearing instead of bush. - most EI systems are relativly similar so go with Boyer, Pazon or the Wassel Vape which has the benifit of being fully encapsulated. - I dont think you will have much problem with a new pair of AMAL Premiers but ensure they are synced and use a twin pull throttle. - Check the valve springs for coil binding after assembly, it's seems to fairly common these days following rebuilds and can lead to bent pushrods etc.
1968 A65 Firebird 1967 B44 Shooting Star 1972 Norton Commando
I’m pretty confident about my con rods. They are the original ones but they’re in excellent condition, highly polished and flawless and SRM are fitting new small end bushes. I will certainly think seriously about billet rods though.
My bottom end was converted to the timing side needle roller with end feed back in the 80’s by SRM and I have asked them to replace the bearing if necessary, although, as the bike has only covered around 6000 miles, I’m pretty sure it’ll be ok.
I already use a twin pull throttle. I think it’s the only way to go with twin carbs and it sounds like you share my opinion on that.
When SRM did the work on my new cylinder head they fitted new guides, valve seats, valves and springs. I will be paying much attention to the set up though, as I have had problems with what you mention in the past.
It’s really good to have this forum for support and I’m sure to be signing up for a proper membership. Learning from more experienced A65 owners is invaluable.
I will make sure to document my rebuild and post photos as I move along with it. Hopefully this will help others with their projects too.
I would say that the standard 473 cam is a great choice, especially since you have one. Since you are paying attention to assembly, making sure the lobe centers are per spec would be time well spent. PRT PS new rods not a bad idea. MAP steel are good and lighter than the SRM alloy ones.
My opinion about it goes with PRT, if you really want to improve your engine install new rods and a stock cam is very good. I don't understand why refurbishing of lower end cost so much if only new oil pump, bearings, rod bolts and gaskets are involved, but know nothing about British prices. All this enlarging of ports and bigger valves to me is a folly, in English circumstances with narrow winding roads you need more torque down low to ride effectively. With my A65 i dreamed about bigger 750 block, until I bought small port head and found torque I never had before. Not only that, but engine started revving much better and accelerated it seemed endlessly. I realized back then my bike is much faster than me and stopped dreaming about more power, just concentrated on brakes to make them better. It was a right move, better brakes and solid suspension allowed me to ride faster and safer, so this is my advice about A65 BSA, based on 10 years of ownership and wrenching.
The stock cam is good, but like most things it can be improved. The race cam is a good alternative if you’ve done all the other work, you’ll feel like the standard setup makes for a slow bike by comparison.
The other alternative is retarding the cam a few degrees ( the mega cycle X2 does just this. It will transform the standard cam, retard it too far though and you get a massive and annoying flat spot around 4000 rpm.
Same comments about the cost though. It is expensive and kinda wish you’d asked on here earlier. Steve Mcfarlane will still do your bottom end conversion if you wanted it done, otherwise I give all my engineering work to a company in Chesterfield. I’ve set them a few interesting projects, the latest one was my A10 crank conversion. It’s still on a bush, and if the bush is done correctly it will give thousands of trouble free miles (the problem comes if it isn’t done correctly) it’s been balanced with a pair of B44 pistons which will give 823cc and fitted with one of John Hill’s aluminium barrels.
I have looked at MAP pushrods online but everything I find says 'NO STOCK'.
Should I be concerned with the quality of SRM's high strength moly pushrods?
Opinions on porting and gas flowing are observed but I do not intend to race the bike, I have plenty of other options if I want to do that and it would be on the track, not the road. Although I do feel I'm getting a little too old for that nowadays. It just hurts too much when you go down, which you inevitably do when you're pushing to the edge of your limits. My last tumble left me in hospital for three days. I would have just walked away from it when I was a younger man.
I had a brand new set of 750 Devimead barrels that I bought from SRM in the early 90's and I wanted to fit them during my current rebuild. I wanted to get the best out of them, so I sought the advice of SRM and went with that. If I'm wrong then time will tell and anyway I have the standard head and 30mm carbs to fit, so it won't take too much work to see what difference the two set ups make. I will certainly make this comparison at some point when the bike is on the road and will report back my findings.
I will try to post an image of the SRM estimate for my bottom end work, so you can see exactly what they are doing, as it is quite an extensive list of work.
The estimate total is £1435.10. On top of this will be the SRM oil pump kit @ £304.99 and a new St/St oil pressure relief valve @ £53.56. So I am, expecting a total bill of getting on for £2K. It may be a little cheaper.
Rest assured that I am spending just as much time and money on the brakes. I do have the luxury of a well equipped machine shop with manual lathes that can swing a spoked 19" wheel on the wheel bearings and jigs for doing the same with the brake plates. It's something that I have done before and consequently never had a problem with my old classic bike brakes. However they are 60's drum brakes and I wont be attempting any 'stoppies' on them. I'll leave that for my modern sports bikes. The last time I had an A65 airborne the mounting threads on one side of the seat pan sheared on landing. I know their limitations and I know mine. I like to think I'm fast but when you get lapped at Donnington by WSB riders it kind of gives you a reality check.
Once again thank you for your advice, it is much appreciated and great brain fodder. I'm always happy to learn from others and always happy to give things a try.
Another word of advice, forget their stainless oprv, I’ve had/seen 3 of them stick. LF Harris is making them now, It’d be worth fitting one of theirs. Look up KBH motorcycles on eBay. They’re about £35
The pump is a decent bit of kit and has become a feature on the engine builds list. When I do them. Their chrome-moly pushrods are decent also and this is what I am using at present.
It will fit, the blow off pressure is 75PSI, the A65's were rated at 50, however for the A70 (which was identical in design, apart from the thrust washer was moved to the timing side) they used the 75psi oprv. The very last A65's may have also used these also but haven't got the information to hand to say with full confidence.
I'll be fitting one to my OIF, A10 crank'ed A65 motor, if you preffered I'd even swap a new LF harris 75psi unit for one of my spare NOS OPRV units.
The standard t120/t140 oil pressure relief valve is fine. (50psi)
Uprating that valve on an end fed motor is asking for the seal to invert With cold oil the standard valve cant relieve enough pressure on a standard motor so when only supplying a pair of big ends it's way over. The higher capacity pump will also add to the problem. The american approach of 'fit the biggest' is not always the correct way to go. Think about the steps you've taken. End fed motor so now no main bush. (30%+ extra capacity from the pump) New oil pump with larger gears than original '66 one. (15-20% extra capacity from the pump) 75psi oil relief valve. (which can only relieve completely at 50-60 C upwards)
To compensate i'd be running 5-30 oil. or even lighter. Don't rev the bike when cold either.
The late a65 rods were shot peened which was a good stress relief method. I f i were spend this amount of money on a bloody old a65 i'd stick new steel ones in it they aren't any more expensive than alloy ones and will last longer. The 750 kit is a good move they run better smoother and pokier with them. There are some decent pistons around for them now too (E+V Engineering) rather than the old GPM ones. If you are changing the cam, the SRM race one is not a wild cam and is tractable with more mid and top, it also doesn't rattle like a tin of nails. With the 750 kit the p'rods are shorter so be aware if going to fancy ones. Years ago i had a 750 jumbo kit that was porous at the rear of the pushrod tunnel and try as i might i couldn't cure it. Sensible mods like mushroom headed tappets are good, Hyde t120 ones are good.but may need shortening. Spend time on the gearbox, the pain of the A65. A 7 plate clutch conversion is also good.
Hi Nick, your 2C is very welcome. Thanks for the input.
I fully appreciate and understand what you are saying about the lubrication system and will take this on board.
I will have a chat with SRM about the camshaft.
I have already ordered the SRM pushrods and they seem to be a good option and I've had good feedback on them and yes they are shorter. As far as the shorter stroke is concerned, I'm more worried about the exhaust system being a little lower on the bike and what implications there are with that. In the past I have experienced problems with getting pattern exhaust pipes to line up properly. I haven't made any real accurate measurements yet but the cylinder head is going to sit about 8mm lower with the 750 kit on. I used to have a problem with my main stand clattering into the left hand silencer, which eventually marked the chrome, so I really don't want them sitting any lower than they did. I think this is inevitable though and I have been advised that it may be the centre stand, or frame stops that are worn and allowing the centre stand to move up farther than it should. I will check this out on assembly and rectify if necessary.
I already have the Hyde mushroom headed adjusters on the top end and also the 7 plate clutch conversion, along with the alloy pressure plate and needle roller lift mechanism.
The gearbox itself will be an area that I intend to go through with a fine tooth comb. It was about the only thing on the bike I wasn't fully happy with on my first rebuild. I didn't pay enough attention to it at that time and although it wasn't as bad as some gearboxes I've clunked my way through, it wasn't great and had a tendency to jump out of gear occasionally.
Certainly if you have money you can proceed with all the work described, but I never heard about necessity of changing flyway bolts and cam bushes. Do your rotor keyway really need re cutting? Instead, I would really think about changing rods, if what you have are original 66 items.. Another necessity not talked about here is incorporating of a real oil filter on your return oil line. Makes quite a difference in reliability of your engine. I had opportunity to open my own A65 engine working without filter for all it's life and after 2 seasons opening it again after a seizure ( crapped E.I. caused it ) but working with oil filter and a difference was eye opening.
Bearings are always the one that gets me when i look at quotes, i have never seen a worn out main roller bearing or a pair of the needle races in the gearbox, yet everyone replaces them. Likewise cam bushes, they last forever or as near as damn it and are a pain to do as it means line boring the pair. Hard to comment really though as we haven't seen the motor stripped so maybe talking out of turn. Oil filter is a must on any engine especially ones with plain bush mains. Not a cheap exercise, getting a motor rebuilt these days though eh?
I often replace idler bushes, I’ve found the odd pair with a lot of slop before now, some have been fine, even with mismatched crank case and inner Timing case.
Never had to replace cam bushes. The first time I’ve replaced gearbox bearings was in this thunderbolt I’m doing, this was because the bearings had been sat in an open atmosphere and rusted, I’ve also changed them if the cases have been vapour blasted also. Never known a set to needed it because they have failed though.
I believe SRM don’t condone the use of oil filters on their builds and specify the use of 40wt oil on the engines. Which is total nonsense.
+1 to above. always used SAE20W50 oil + oil filter and my engine after 20 k miles worked the same ( or better ) as a day I started it for the first time. And it still works for a next owner, who called me with some questions and congratulate on the quality of a rebuild.
My engines tend to use a modification to re-direct the OPRV vent to the rocker/head feed. I hate the idea of just circulating oil from the pump back to the tank without it actually doing any work. Any oil sent up to the head aids cooling. But that's just my opinion, i've done this for years on race and road motors. You will find on an end fed motor the OPRV is open at anything over about 2k rpm just dumping oil into the sump and returned to tank, wasted energy and no bloody use at all. Doing this also gets the oil up to operating temperature faster so flow is increased. I think Dave Madigan makes a pukka block to achieve this but i just use an old ball type valve and run a pipe from a fitting in the end. A setup like SRM probably had a load of problems with blokes fitting filters in the wrong place etc and using incorrect oils so the easy way to stop that is to advise like they do. They are running a business doing loads of these for all sorts of people, return problems need to be minimal.