How very true, but people ride and modify British bikes for all kind of crazy reasons.
I'm guilty of this, too. But this current thread isn't (just) about modifying a BSA for crazy reasons, it's about finding 25 people who not only have the identical crazy reason, each also has has ~$2000 to pursue it.
Originally Posted By: Redd32
Why not just buy a modern Jap mike?
The reason I used a Ducati Monster 600 as an example is that it has roughly the same weight and displacement as a BSA 650, and my guess is that most people who have BSA 650s would prefer a European bike.
This is a bit far away from the original questions, but you would buy a Ducati over a Japanese bike for one very good reason:
A European bike is acceptable to show up on at British gathering where a Japanese just doesn't cut it. When Vincent parts weren't that reliable they would ride a Ducati, BMW or other European bike to a rally. You wouldn't even think about showing up on a Honda. Well, except if you are like me.
IMHO it is just one of the reasons the new Triumph is doing so well.
I don't have my little gear calculator program handy, but your ratios are a b it taller than what I am using on the twisties of SE Ohio......
Alex used a CR BSA box at Daytona, the gearbox worked better than some other things He did get some good starts though.
Reality is, there are too many variables for a cut and dried 5 speed. Least of all is the front money. Lot of dreaming here........
And the modern bike thing.....yea I did it. A Triumph Tiger 800XC scratches a lot of the right things for me. And it has a CR 6 speed......what a sweet gearbox and engine. But I did ride my BSA with the CR box yesterday......that bike is a hoot to ride. But I would guess most people would not live with the CR box on the street.....
..I agree that the stock A65 ratios are fine for the street. ......
adding a fifth gear between 2nd and 3rd would improve things greatly for the road....
A 21 tooth gearbox sprocket, then a slightly lower 1st, 2nd as is or slightly lower, a 3rd between original 2nd and 3rd, then a 4th slightly higher than original 3rd, then of course, 5th.
Thus eliminating the annoying gap between 2nd and 3rd. Other benefits of these ratios with the 21 tooth would be less clutch slipping or disengaging to slow when in slow traffic....
Slightly different ratios for 2nd and 3rd would do almost as well.
Thanks for posting this Bill (I have edited out some of your post) The RPM drop between 2nd going into 3rd is about 2000 RPM, and is felt more with taller gearing. It is hindered further still (at least in road use) if you are working with large ports whilst you may gain in H.P at some high RPM, your power band is very much reduced (the reason why I don't ever give a snot about that the HP on something is, but how wide the power band is!) That 2000 rpm drop is the killer on a BSA, and whilst it can creep up to about 100mph eventually with the settings it rolled out of the factory with, you are out of the power band which moved you up to the 70-80mph in the first place, possibly why the CR box works so well, because the 2nd gear is now a 85-90mph gear and the RPM drop is about 1000 rpm.
Whilst we are deliberating the Quaife ratios, (and no disrespect to your post John) the ratios would have been tried and tested for the use it is designed for, we don't know what use/track type the box was designed for (the bit that links in with Johns post).
What my young and ignorant mind doesn't understand with:
Originally Posted By: John Healy
So besides matching the ratios to the torque curve of the engine, whether it be for street use or road racing, which is essential, there is more to think about when selecting ratios. The heyday of AHRMA at Daytona with elbow to elbow racing with novices using lines know only to themselves and the guardian angel that protects them, is not the Isle of Man where you might pass a half a dozen racer per lap.
Is if you are optimising the ratios to change at the optimum point for best acceleration, how can this change between track types? I can understand changing sprocket ratios to close things up a bit on a short circuit, or widen the ratio for a long track like the IOM.
Alan, in our type of vintage racing getting to, if not at, the front into turn one is the most important thing you can do. Failing this you will seldom podium. I don't care how much of an expert you, how much more horse power you have or how fast your corner speed is, you are risking it all trying to make your way up to the front.
Most of our vintage races are sprints of 6 to 10 laps, even at Daytona. There is no time to make your way through 20 or 40 "racers", half of them who shouldn't be on the track in 6 laps to make your way from the back to the front.
AHRMA, and most of the other vintage clubs in the US, break the riders up by class, not experience. Using a true close ratio 5 speed,commonly used in the UK, you better have a pair of big ones if you find yourself lined up in row 8 and expect to win. By the time you finishing slipping the clutch to get the bike moving everyone has "left the gate."
Also the torque curve on a short rod 750 Triumph is quite wide. At Daytona we only use 1st for the start. Jerry carries enough corner speed through the slowest corner at Daytona where first isn't necessary. And with the width of the power band the 4 remaining gears, with a stock gear set, the bike is never out of it. The bike pulls from 4,000 to 6,000 quite nicely.
Allan, winning races is more than having the most power. It is understanding all of the factors that will allow you to win. If you cannot get to the front, you are not going to win. Although Steve Maney eventually went on to win Daytona he learned a big lesson running against Keith Martin's 750 Triumph. Keith had earned a place at the front of the first wave, I think is was row 2, by attending previous AHRMA races. Steve being from the UK had no previous AHRMA experience that year and was in the middle of the grid mounted on a first class bit of kit.
On the start, Steve slipped the clutch and paddled his way until his close ratio 1st gear finally hooked up with the power band. After several laps he worked his way through the rolling maze of experts and novice riders up to the front, or what he thought was the front. Meanwhile Keith Martin's rider, Dr. Rob Tuluie - yes, he is a rocket scientist, had got a perfect start and had broken away from the pack and was completely out of Steve's sight. COMPLETELY.
I am sure that both bikes were competitive with each other, but in the time it took Steve to work through traffic, Rob had flat disappeared. I was standing in the pits when rob came in (Jerry had captured third from the second wave), and Rob was finishing his interview with the announcer when Steve came motoring down pit road. Steve was visibly shaken when he saw Rob being interviewed as he thought he finally had a Daytona win. I think he still thinks he won!!! Keith understood the job at hand, and Steve learned a pain full lesson. It not all in the books...
Yeah Rich...a CR would be just what I mean...if you could stuff a lower 1st in there. Making it a 5 speed! John, I preciate what you're saying but again, I won't be racing my Tbolt. Only thing I have to outdrag is an occasional 4 wheeler at a light. I suspect some others would like to have this gearing also for similar reasons. Hey Magman...would love a Duc. Rather it would be a 900 Monster tho. Apples and oranges I think... I have a modern bike. It's an '85...heh
69 A65T 71 B50T 85 K100RS 54/59 A10SR 69 B44VS 71 A65FS Too much moderation is bad for you.
I fully appreciate where John is coming from, The kind of guys who would be more ready to spend some money on a box would be the racing guys. I think we are all on the same page though that a lower first gear is required, whether it is helping us leave the start line, or crawl along in slow traffic. A lower than stock 2nd gear would be ideal on the street, and a 3rd gear somewhere between stock 2nd and 3rd, lower 4th (which the quaife has) and 5th sticks at 1:1
Some alternate ratios I had been playing about with, of course we know nothing until they have been tested, but they put the first 2-3 gears are under 100mph gears (depending on overall gearing) and expecting a good bike to rev out at 7500 rpm in the lower gears. then keeping the Quaife 4th gear which looks nicely spread. First gear is lower than stock, im not overly sure about 2nd it has a 600rpm drop when changing from first, but has a drop of about 1500 rpm when changing into 3rd (which is the 4 speed CR box 2nd gear ratio)It drops again 1500 rpm into 4th and 1100rpm into 5th. It should keep a nice even(ish) spread - easily suitable for roadwork in my view, but should keep a bike within its power band.
I have used on the road 19:47, 21:47, 22:47 ratios on A65's the 19:47 setup in first and second gear are really good for getting your nail down (with a quick burst of throttle on a slightly gravely surface, the back wheel soon spins up) but its brilliant in traffic - never having to slip the clutch.
Allan, I think your first gear ratio is unrealistic. To get a 2.76:1 ratio the first gear set would have to be 25/13 with a 23/16 high gear/layshaft. The first gear pitch diameter is 9.75 which can be cut with a 10 PD cutter and special addendum, however the root diameter of the mainshaft gear would be 1.105". With a 0.980" mainshaft diameter it does not leave much material at the base of the teeth to keep it from exploding. The real problem with the Quaife box is the 3-4 gear step. The RPM drop from 7500 RPM shifting through the gears is: 1-2 1948 RPM 2-3 1435 RPM 3-4 753 4-5 1427 RPM The huge step from 4th to 5th is alright for an overdrive ratio but you will have to shift pretty quick after 4th. I get a slightly different top speed. With a 58/28 primary, 1/1 gearbox, 19/47 secondary and 26" tyre diameter, at 7000 RPM I get 115.5 MPH (123.7 MPH at 7500 RPM)
I was saying that out of sarcasm. I ride a 69 Triumph Bonnie,and have a 69 BSA lightning(not running yet). I trade bikes with younger riders with modern Jap crotch rockets, And they have favorable things to say about my old bike,to my surprise. I warn them when they get on it is an antique. Yes it would be easier to ride a Jap bike, but I like the British bikes.
Not for A65s but many of the Gold Star guys use the Nova 5 speed conversion. You gents may find this interesting. It can be ordered with close ratios for racing or wider ratio spreads for the road bikes. Several GS riders I know are very happy with their Nova's. I envy them, even tho my 'Daytona' DAY T, 4 speed semi close gear set works nicely and corrects the wide spread between 2nd and 3rd in the common STD box. aaargh. It amazes me BSA didn't fit this gear set as OEM especially in Goldies. hmmm
I like my vintage Brit rides too, but, my aching joints (especially the fingers) don't handle the late fall/early spring ride to work in the early morning. So no modern Jap, but modern Brit instead. There is something to be said for windscreens and heated grips @ 6:30 am when it is 33F outside.
There is also something to be said for less wear & tear on the vintage bike most days commuting to work. Keep the vintage ride for enjoyment, the modern ride for the day to day grind
Not to bring up a long beaten subject again but here is a picture of the drawing so far (no, I am not drawing gear teeth as it adds nothing to the machining detail. The company cutting the gear teeth and splines will take care of that>)
It will use the stock T140/T150 sprockets which will move the sprocket out 0.050" but that should be easy enough to correct with wheel spacers if required. Or the T140/T150 sprocket nose can be shortened.
Quaife will still make a box, but the ratios are a bit odd. Without looking back through the notes there is too much of a gap between 4th and 5th - so I can imagine the rider will seldom get the bike into top.
Using the BSA CR ratios but 2nd CR becoming 5 speed 3rd, and so on and a new 2nd gear which is in between the CR 2nd ratio and std first would have been a nice spread on power for any occasion IMO. (STD 2nd is too much of a drop into STD 3rd when you've got the throttle to the stop)
I also remember one sidecar guy fitting a triumph pre-unit box with a 5 speed cluster behind his cut-off a65 engine that was back in the UK in about 1978. That is an easier path to go down as the cluster is a doddle to fit and cutting off the box gives you masses of room to fit the complete assembly in, it's just fabrication and good welding jig etc.
I did consider that. but with one of the Nova boxes off an A10 like Dave-NV mentions. Although I can't face myself to start chopping like that on a bike. That said, IF I do use an A10 frame on the future project, have the problem will be sorted.
The T140 5 speed has different shaft centres than an A65, 1.915" versus 2.0". You would have to move the layshaft bearing on the drive side closer to the mainshaft. The T140 width is 0.91" wider which can be spaced by moving the T/S door however it causes domino effect on the inner cover. Why not just cut off the A65 gearbox and graft on a Triumph 676 6 speed? Or, as Norton did on the F1 rotary, use FZ1000 internals in a new case?
I see a trend to convert Triumph 650s to five-speed gearboxes. From my own experience, however, the conventional triumph 4-speed gearbox was sufficient due to the torque of the 650 engine. Where a five-speed would have been more useful would be in a 500cc unit Triumph. Having owned four Triumph 500s I can appreciate the better performance flexibility a five-speed would have given each of them.
So now I am curious as to why you tried to put a Triumph 5 speed in an A65 if 4 were enough? It does not matter what gear you are in. If you are at red line and have to go faster, shift up. If you are not accelerating fast enough, shift down.
What is the red trace DM is it a Triumph 5peed or something else it looks like 4-5 is similar to the std BSA 3-4 which is nice. My latest ports give such a wide spread of good power my big engine hardly needs more than 4 speeds, C/R 1st and second make it nice and 3.43-1 final drive make it quite fast. I should do a data run and see what its actually got but I don't want to hurt the thing when it's going so nice..
The red trace is the ratios for the A65 5 speed that I am building. I looked at C/R gearing but as John pointed out, it is a drag race to the first corner. Besides, this makes it useful for the street too.
it looks like 4-5 is similar to the std BSA 3-4 which is nice.
it looks like a nice spread on the gearing. Looks like a good road setup. Your standard ratios look quite tall, however I was running 21:47 with a 26"D tyre but 80mph was 8000 RPM (and the GR calculator confirmed that) or are you displaying the 4 speed setup from a CR box?