Delightful wee lassies! I’m a Metallurgist but I ain’t no Engineer, however, I’m sure you are doing the right thing re-building the engine because your A70 is so good looking it deserves to have a sweet running motor 🇬🇧🏍
I know I’ve read about the misaligned machining on the oil return but I’ve never understood it until seeing your video, so thanks for that! Bummer about the TS bush. I’m in the same boat with my A50. So much to love about the design of the unit twins compared to the triumph but they really mucked it up when they decided to stick with that darn TS bush as the oil path.
Excellent show, nearly got my hands on the lightning , but was too slow ended up with the 1975 bonnie which I can’t fault. The boy i bought it from also goes by the name Angus, a movie producer from Glasgow.
Hi Angus. The A70 oprv is the same as the same as the trident oprv. And in agreement the spec for it is 70psi blow off pressure. Unlike the A65 which is 50. Interestingly I had the same issue as you have had and from following the same advice as yourself. I have always used a thicker copper washer prior to this advice and since have reverted back to using one as it has given me Zero problems like that. This is on a 68 and a 71
hi Angus you get solid bronze bushes for the timing side which use better material than the original bronze they used, but you'll need to get it line bored to mate up with the drive side bearing, so there's no run out/ misalignment on the crankshaft resulting premature wear of the bush. Ady.
Hi Angus, My heart bleeds for you mate, but you'll get there. The inboard thrust washer/bearing is shown on the cutaway diagram. It's just not part numbered as a special A70 item because it's the same as the A65. I would suspect that the flange on the timing side bush is also the same as the A65, so in theory you only need to machine the length of the bush to make it fit. Burton bike bits did have some -10 A70 bushes as I bought one as a spare for my A70. I do hope you keep the bush and not go for the needle roller conversion as it's one of the defining aspects on the A70 engine for good or bad, but please fit a cartridge oil filter on the return in order to offer it some protection. Jim
Being a retired mechanic, I find your posts really interesting, although I don't have a bike anymore. I realise this is now done and dusted, but, when you were pondering the relief valve free length, it occurred to me that the longer spring was for use with a ball, and the shorter one for the plunger type. Just a thought. Maybe they mixed and matched to get the higher press required.
Hi Nigel and thanks for the post and the compliment - I’m self taught so I’m sure make plenty of mistakes or go about things in an illogical way but I usually get the job done and the bikes running reasonably well. I agree you need to be careful with the OPRV springs, ratings and lengths. I’m pretty sure now that the A70s is the same as the A75 rating wise but the part numbers are not the same although that could be down to other matters not the spring and plunger. Agree that ball/plunger will require different length springs. Perhaps the factory did mix and match existing parts components - it wouldn’t surprise me.
Hi Angus, the non return valve isn't the PRV it's the daft ball and spring that's supposed to stop wet dumping! Good luck with the rebuild, on the A7 we went for the next oversize and machined back to fit followed by a scrape to give a nice fit.
Reducing bearing surface area to squeeze in a bigger crank? A whiff of desperation at BSA there … higher film strength ester-bases oil should improve the chances of survival once you’ve rebuilt it. Looking forward to that Fury start-up in the meantime!
Hi Fred and Walt - it is a candidate but for the mileage it will do when done and with the correct regular servicing and oil changes I’ll give it, I’m sticking with the original layout. Thanks for the comments and interest.
Nice video, I guess that was the problem, them bushs were never any good,triumph fitted them ,found out they were crap then changed to a proper bearing,no more issues, just look at the racing tridents ,great crank bearings...when you get another bush ,try to find a proper engineer who can carry out the work correctly using accurate tools and machines,not a bodge job. Then it might last a couple of hundred miles..... lol ....all the best mate.
It's a pity you are in Midlands, I'm in east monmouthshire and I could grind a few thou off the crank on my jones and shipman and make a bespoke timing side bush for you
That's a kind offer Wayne - thank you. East Monmouthshire isn't a long drive at all - I was in the Wye Valley for a long weekend over the summer. Considering I've been driving 8 hours several times to get to and from the Scottish Isles, your area is a walk in the park. Another video is coming shortly on the A70 following which it will be decision time - take it apart again or not! Thanks again.
Every report on the A65 I've ever read states the timing side bushing is prone to premature wear. Your machine not only is doing this as per reports but also from the fact the bike was thoroughly thrashed before you got it. Does someone else currently make a bearing of better material that could be machined to your needs? Also, I still believe that once the bearing issue is corrected then using a modern motorcycle engine oil such as Red Line Synthetic motorcycle oil (which the Norton Club of California tested some years ago) would circulate and protect far better than whatever was available in 1971.
Thanks for the interest, comment and info John. I’ll be investigating bearing material options once the motor is apart and also types of modern oils, but as the mileage will be low then I’ll probably stick with a machined down standard A65 bearing. But let’s see.
@@BSAPowerSet Seriously, BSA was on its deathbed and they may have been cutting corners at that point; seen it many times. If there is a better bearing out there, I would go for it. The California Norton Owners Club tested many different oils in the late 1990s and the Red Line Synthetic proved far superior on their engines than all the others. I believe their results are still available on-line. If I still had my Triumph I wouldn't dream of using the same oil today I would have used in 1976 when there are far superior viscosity and detergent/dispersant oils available today.............just saying. Press on! and sorry for pontificating.
Gordon Brown's comment (below) made a lot of sense if what he says is correct that the A70 TS bush was different from the A65. I'd follow up on that. I would almost bet that there must have some upgrades done outside of BSA since the company's demise. The amount of time and effort you've already put into this machine means you know where this is going--and I'll bet you don't like it. But afterwards you will have the most perfect A70 on the planet.
@@johndonlon1611 Oh yes John the TS bush on the A70 is not quite so wide as the A65. Also yes there are very good aftermarket upgrades from SRM; however I'll stick with the standard setup as the bike will obviously be Molly coddled in my possession!
Sorry to bother you again Angus - but you seem to be the expert to consult. A few month ago I bought myself a 1971 A65 FS (before that I was engaged in triples from1978 on). So how are the A65's responding to modern lead free fuel? Do I need stelite valve seats as I did in my 3 cylinder racers? Or can I run it as is on the road? What do you think about the oil filter kit that fits into the frame at the bottom? Any good or not? Thanks.
No problem. I’ve never changed any valve seats nor used any lead additives but do run all bikes on the highest octane I can get - usually 98/99 super unleaded at local outlets. Re the oil filter kits i was going to fit one of those myself on the A70 until I realised you need to modify the standard internal pickup tube. There’s a lot of discussion on forums about the efficacy of fitting a full flow filter on the feed side rather than a screw on type kit on the return but I can’t comment from experience as I run the bikes standard and just change the oil very regularly. Of course the B25SS and E35R/SS have full flow cartridge filters as standard.
Hi again, I forgot that the A70 had a different size of TS bearing, in the past I have pressed out the worn Bush , machined up a replacement with modern PB , pressed that in and machined to suit, that may be a better solution in this instance rather than machining down the A65 one?
Hi Gordon - thanks - yes I am considering whether to have a friend machine up a pattern bush rather than modifying an A65 once we press out the original.
Hi Angus, defo needs saving from itself as a rare example, BSA really found the limits of the design (weakness) hard to believe any of the 200+ for homologation lasted that long!
Hi and thanks. Agreed it was a weak point before the A70 mod but the A70 was designed to go like bloody hell for five mins before being rebuilt for the next race.
Indeed Andrew - a weak point on the A65 made weaker on the A70 - they were desperate to get the 750 homologated hence the minimal changes - against the advice of a number of personel at the factory at the time. There's an interesting section on this subject in Peter Crawford's book Thunderbolts and Lightning. Thanks for the interest.
@@BSAPowerSet Yes, as an engineer, it annoys me when management decisions to cut costs are reflected on the designers/engineers. There are many examples of superb motorcycles built in England, when the bean counters are locked out of the room!
Not that I know of. You’d have to get the paint matched at a modern paint shop. My bronze is a little darker than standard and the stripe is too orange rather than the original pinky orange. But I like it and more importantly so does my daughter!
Hi, all the very best with the work on your A70. Such a nice and Interesting bike i Love. And wishing your Dad a Speedy recovery. God bless. Cheers TC
Very many thanks Alistair - appreciated.
Delightful wee lassies! I’m a Metallurgist but I ain’t no Engineer, however, I’m sure you are doing the right thing re-building the engine because your A70 is so good looking it deserves to have a sweet running motor 🇬🇧🏍
Many thanks Stewy.
I know I’ve read about the misaligned machining on the oil return but I’ve never understood it until seeing your video, so thanks for that! Bummer about the TS bush. I’m in the same boat with my A50. So much to love about the design of the unit twins compared to the triumph but they really mucked it up when they decided to stick with that darn TS bush as the oil path.
Agreed Matus. Thanks for the comment and interest and best wishes with the A50 rebuild.
Excellent show, nearly got my hands on the lightning , but was too slow ended up with the 1975 bonnie which I can’t fault. The boy i bought it from also goes by the name Angus, a movie producer from Glasgow.
Many thanks Patrick. Yes there’s a few of us in Scotland! Glad you enjoy the Bonnie - I bought a new T140D in 1978 and loved that bike.
Hi Angus. The A70 oprv is the same as the same as the trident oprv. And in agreement the spec for it is 70psi blow off pressure. Unlike the A65 which is 50.
Interestingly I had the same issue as you have had and from following the same advice as yourself. I have always used a thicker copper washer prior to this advice and since have reverted back to using one as it has given me
Zero problems like that. This is on a 68 and a 71
Thanks Mac for the comment and interest and for confirming the OPRV spec. Also for sharing your experiences.
hi Angus you get solid bronze bushes for the timing side which use better material than the original bronze they used, but you'll need to get it line bored to mate up with the drive side bearing, so there's no run out/ misalignment on the crankshaft resulting premature wear of the bush. Ady.
Hi Ady - yea appreciate it should be line bored whichever type of bearing/material I use.
a big hello m8 from the south of France 😜👍
Hi Mick. Enjoy and drink a good claret for me. 🍷
Great. I learned something new about the misalignment at the press release valve oilline. Lovely Gaelic girls,I like to learn more gaelic.
Cheers Torbjorn.
Hi Angus, My heart bleeds for you mate, but you'll get there. The inboard thrust washer/bearing is shown on the cutaway diagram. It's just not part numbered as a special A70 item because it's the same as the A65. I would suspect that the flange on the timing side bush is also the same as the A65, so in theory you only need to machine the length of the bush to make it fit. Burton bike bits did have some -10 A70 bushes as I bought one as a spare for my A70. I do hope you keep the bush and not go for the needle roller conversion as it's one of the defining aspects on the A70 engine for good or bad, but please fit a cartridge oil filter on the return in order to offer it some protection. Jim
Hi Jim and thanks for the comment and info - appreciated. I will be sticking with the standard setup.
Being a retired mechanic, I find your posts really interesting, although I don't have a bike anymore. I realise this is now done and dusted, but, when you were pondering the relief valve free length, it occurred to me that the longer spring was for use with a ball, and the shorter one for the plunger type. Just a thought. Maybe they mixed and matched to get the higher press required.
Hi Nigel and thanks for the post and the compliment - I’m self taught so I’m sure make plenty of mistakes or go about things in an illogical way but I usually get the job done and the bikes running reasonably well. I agree you need to be careful with the OPRV springs, ratings and lengths. I’m pretty sure now that the A70s is the same as the A75 rating wise but the part numbers are not the same although that could be down to other matters not the spring and plunger. Agree that ball/plunger will require different length springs. Perhaps the factory did mix and match existing parts components - it wouldn’t surprise me.
Hi Angus, the non return valve isn't the PRV it's the daft ball and spring that's supposed to stop wet dumping! Good luck with the rebuild, on the A7 we went for the next oversize and machined back to fit followed by a scrape to give a nice fit.
Thanks Gordon - understood.
Reducing bearing surface area to squeeze in a bigger crank? A whiff of desperation at BSA there … higher film strength ester-bases oil should improve the chances of survival once you’ve rebuilt it. Looking forward to that Fury start-up in the meantime!
Thanks Monza. Fury start up will be this month.
👍@@BSAPowerSet
might it be a candidate for a devimead /srm ball conversion
The SRM conversion seems like they say to go. That's what the factory did to the race bikes.
Hi Fred and Walt - it is a candidate but for the mileage it will do when done and with the correct regular servicing and oil changes I’ll give it, I’m sticking with the original layout. Thanks for the comments and interest.
Nice video, I guess that was the problem, them bushs were never any good,triumph fitted them ,found out they were crap then changed to a proper bearing,no more issues, just look at the racing tridents ,great crank bearings...when you get another bush ,try to find a proper engineer who can carry out the work correctly using accurate tools and machines,not a bodge job. Then it might last a couple of hundred miles..... lol ....all the best mate.
Cheers Matt.
It's a pity you are in Midlands, I'm in east monmouthshire and I could grind a few thou off the crank on my jones and shipman and make a bespoke timing side bush for you
That's a kind offer Wayne - thank you. East Monmouthshire isn't a long drive at all - I was in the Wye Valley for a long weekend over the summer. Considering I've been driving 8 hours several times to get to and from the Scottish Isles, your area is a walk in the park. Another video is coming shortly on the A70 following which it will be decision time - take it apart again or not! Thanks again.
Every report on the A65 I've ever read states the timing side bushing is prone to premature wear. Your machine not only is doing this as per reports but also from the fact the bike was thoroughly thrashed before you got it. Does someone else currently make a bearing of better material that could be machined to your needs? Also, I still believe that once the bearing issue is corrected then using a modern motorcycle engine oil such as Red Line Synthetic motorcycle oil (which the Norton Club of California tested some years ago) would circulate and protect far better than whatever was available in 1971.
Thanks for the interest, comment and info John. I’ll be investigating bearing material options once the motor is apart and also types of modern oils, but as the mileage will be low then I’ll probably stick with a machined down standard A65 bearing. But let’s see.
@@BSAPowerSet Seriously, BSA was on its deathbed and they may have been cutting corners at that point; seen it many times. If there is a better bearing out there, I would go for it. The California Norton Owners Club tested many different oils in the late 1990s and the Red Line Synthetic proved far superior on their engines than all the others. I believe their results are still available on-line. If I still had my Triumph I wouldn't dream of using the same oil today I would have used in 1976 when there are far superior viscosity and detergent/dispersant oils available today.............just saying. Press on! and sorry for pontificating.
@@johndonlon1611 No problem John - appreciate all the views and experiences. Thanks.
Gordon Brown's comment (below) made a lot of sense if what he says is correct that the A70 TS bush was different from the A65. I'd follow up on that. I would almost bet that there must have some upgrades done outside of BSA since the company's demise. The amount of time and effort you've already put into this machine means you know where this is going--and I'll bet you don't like it. But afterwards you will have the most perfect A70 on the planet.
@@johndonlon1611 Oh yes John the TS bush on the A70 is not quite so wide as the A65. Also yes there are very good aftermarket upgrades from SRM; however I'll stick with the standard setup as the bike will obviously be Molly coddled in my possession!
Sorry to bother you again Angus - but you seem to be the expert to consult. A few month ago I bought myself a 1971 A65 FS (before that I was engaged in triples from1978 on). So how are the A65's responding to modern lead free fuel? Do I need stelite valve seats as I did in my 3 cylinder racers? Or can I run it as is on the road?
What do you think about the oil filter kit that fits into the frame at the bottom? Any good or not?
Thanks.
No problem. I’ve never changed any valve seats nor used any lead additives but do run all bikes on the highest octane I can get - usually 98/99 super unleaded at local outlets. Re the oil filter kits i was going to fit one of those myself on the A70 until I realised you need to modify the standard internal pickup tube. There’s a lot of discussion on forums about the efficacy of fitting a full flow filter on the feed side rather than a screw on type kit on the return but I can’t comment from experience as I run the bikes standard and just change the oil very regularly. Of course the B25SS and E35R/SS have full flow cartridge filters as standard.
Hi again, I forgot that the A70 had a different size of TS bearing, in the past I have pressed out the worn Bush , machined up a replacement with modern PB , pressed that in and machined to suit, that may be a better solution in this instance rather than machining down the A65 one?
Hi Gordon - thanks - yes I am considering whether to have a friend machine up a pattern bush rather than modifying an A65 once we press out the original.
Hi Angus, defo needs saving from itself as a rare example, BSA really found the limits of the design (weakness) hard to believe any of the 200+ for homologation lasted that long!
Hi and thanks. Agreed it was a weak point before the A70 mod but the A70 was designed to go like bloody hell for five mins before being rebuilt for the next race.
For anyone wondering why the British bike industry failed ..........
Indeed Andrew - a weak point on the A65 made weaker on the A70 - they were desperate to get the 750 homologated hence the minimal changes - against the advice of a number of personel at the factory at the time. There's an interesting section on this subject in Peter Crawford's book Thunderbolts and Lightning. Thanks for the interest.
@@BSAPowerSet Yes, as an engineer, it annoys me when management decisions to cut costs are reflected on the designers/engineers. There are many examples of superb motorcycles built in England, when the bean counters are locked out of the room!
Just love the girls commenting - so I must be investigated now.
😮
Another question: is there a color code for the Etruscan bronze and the dayglo stripe on the tank?
Not that I know of. You’d have to get the paint matched at a modern paint shop. My bronze is a little darker than standard and the stripe is too orange rather than the original pinky orange. But I like it and more importantly so does my daughter!
Within tolerances?
Timing side main bearing and journal dimensions.