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70 BSA A 65 Lightning discussion forum:modifying a 1970 A65 Lightning |
| modifying a 1970 A65 Lightning |
| mark said 2004-08-28 18:48 |
| Hi, I have owned and ridden BSA 650 twins since I started motorcycling in about 1970 with a ´50 A10 golden flash. The A10 recieved a thunderbolt power unit after throwing a rod. The next A65 was basically a lightning built from various bits, and I set about doing anything one could without the aid of money to extract more power from it,exhausts, 32mm carbs, the various tuning articles I read said it was a wast of time going bigger than 32mm, they were so wrong! but I didn´t find that out then. Instead I read about the Rocket 3´s, especially the race ones, how fast they were, so I set off after a triple. And swaped my going A65 for a wrecked Trident which standard didn´t go as good, a few years later it had a good exhaust, 32mm dellortos,big valves, 867cc kit, etc, and was very fast, especially when I, and I know it´s probably heracy, dropped the motor in a modified early VFR rollong chassis which matched handling with the power, the std T150v was to light in the front and probably flexy, the honda frame fixed that. I thought as do probably many that the three cyl is a better power unit to use if you seriously want to go fast, but I´ve come to revise my thoughts on that and believe the A65 is at least as good and in some ways better. For I had aquired a 1970 lightning as payment for a job, and having the triple for transport I didn´t have much fear of going a bit radical with the A65. The way it is now it stops and handles better than most things, RGV´s are good at that, it has a very strong midrange and bottom end, long stroke motors (89mm) work good there, especially if they have bigger inlet and exhaust valves, matching them with extensive portwork, 38mm carbs, and bigger dia tuned exhausts keeps the power good to around 7500, it doesn´t seem to want to blow up anymore because the 90deg crank is dynamically better, we cut a std a65 74mm crank in half and bolted it up at 90 deg and my son Ben persisted in reving it to 9000, at that stage his motor was 650 but otherwise the same as mine, though with 38mm flatslides, his didn´t go much below 5,000 and was very power bandy, really taking off between 5000 and 9000. Anyway that is my story about my 1970 lightning I should work out some performance data for you, it runs a 21t front sprkt and 36t rear and has c/ratio 1st 2nd gears so you can probably work out I don´t live in the city, I often see 60 MPH in first without particularly reving it hard and second will exceed 100, on the highway as long as it´s doing 60 mph it can be left in top, hills don´t exist, that is where it´s better than the triple. It weighs around 160kg with some fuel. If anyone is interested I could send a photo. My opinion is that BSA could have built a better race bike for F750 by developing the A65 rather than the triple, It could have been lighter with all the associated benifits and been equally as powerful. The most unreliable aspect of it is top gear which has broken 3 times in the past 12 years, though it does get used virtually every day. all the best Mark. |
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