New 5 speed gear cluster for the BSA A65. Based on original gear cluster technology, xxxxxxxxx and has also been further enhanced to incorporate many of the design benefits gained by their experience in the world of international moto-cross with BSA large bore single cylinders engines.
Along with suitable spaced ratios of 1st 2.222:1, 2nd 1.597:1, 3rd 1.296:1, 4th 1.111:1 and 5th 1:1. Other benefits include: a)Splined mainshaft with an adapter to suit the BSA clutch. No longer will you need to worry about the key shearing or having to torque the clutch center nut up to 75 ft lbs. b)All meshing gear dogs are back cut for positive engagement, and no longer rely on the cam plate and selectors to maintain engagement. c)Final drive sprocket is supported on both sides by bearing, while the drive gear is running on needle roller bearings. d)All rolling gears run on needle roller bearing, no longer are gears running on brass bushes.
The new 5 speed gear cluster and selector system comes complete with clutch center adapter and new bearing mounted clutch back plate to support both sides of the final drive sprocket. xxxxxx
To go with a 5 speed cluster. xxxxxxx Ltd are also developing a new light weight clutch. That will offer a more effective clutch, with lighter action and superior chain alignment.
If any one can get this off the ground its John, more power to your elbow sir. As one of the first recipients of the alloy barrel conversion I can vouch for Johns high quality and well thought through approach to engineering solutions for these old twins. I may even be the first to get one of the big bores up and running but thats a different thread.
Now I need to think up an excuse to get one of those conversions. My 71 OIF has a very sweet box which works so well I can select neutral at standstill when warm. However the NorBSA has issues with the clutch. hmmm.
Ive had some interesting chats with John over the phone around this topic, I know how much thought and research he has done already, for most of us A65 owners this is too good an opportunity to be missed, I imagine this would be a boon to any would be classic racers out there.
Best of luck with this for the future John.
71 Devimead A65 750 56 Norbsa 68 Longstroke A65 Cagiva Raptor 650 MZ TS 250 The poster formerly known as Pod
I'd love one of these. What excellent ratios, this sounds such a great thing for A65 owners. It makes such a difference when a gearbox is helping a motor stay in its good rpm zone. Like Gavin, I have C/R 1st and 2nd in my A65 which makes a big improvement, but this sort of 5speed would be, yea, what Nick says. An 80 x 74 744 A65 with these ratios could be such a sweet and potent thing.
5-speed cluster; why these ratios would be so nice. I did a little calculating. This is using 20t 38t final drive sprockets with an envisaged 744 A65 hotrod(the final drive ratio we have used with a 650cc 90deg A65 engine in an RGV chassis.) The effect is the same with a different final drive ratio. Using a theoretical motor that makes peak power at 7800 or above. This example uses 7800 as a change point, changing at lower RPM the effect is still much the same. Its important to realize the faster you go the more HP you use to maintain the speed. So the first to second change can be the widest because the thing will not be using much HP to maintain 70MPH and hitting second at 5606RPM will be in good HP with lots to spare even if it has an extra twenty or thirty HP beyond 7000. By 4th gear though speed is up and the extra HP left over to accelerate the thing will be getting more scarce, (riders notice the gap between 2nd and 3rd on the std box because at lower RPM it can drop you out of the power)however going into 5th with the 5speed only drops RPM back to 7020, into an area closer to where the most power is produced and where the best chance is to have some extra HP available to accelerate the thing a bit more. If it went into top and revs dropped to 5606RPM it may not even have sufficient power to maintain the speed.
Gear ratio MPH at 7800RPM in gears 1st Gear 2.222 From 1st @ 7800 68.98 2nd Gear 1.597 Into 2nd @5606 95.98 3rd Gear 1.296 Into 3rd @6330 118.26 4th Gear 1.111 Into 4th @6686 137.97 5th Gear 1.000 Into 5th @ 7020 153.30
Original A65 ratios for 4-speed cluster Ratio MPH at 7800 in gears 2.513 From 1st 7800 61.01 1.599 Into 2nd 4964 95.87 1.145 Into 3rd 5585 133.91 1.000 Into 4th 6813 153.30
DD - ? Direct gearboxes drive through two sets of gears for everything except top gear which locks the high gear to the input shaft. It could be rearranged so 4th is 1:1 and 5th overdrive. Mark, I have the standard 4 speed 2nd as 23/36 (1.5294) which gives 100.23 MPH.
One thing I forgot to mention in the original post. Is that this system is only good for the later models with the speedo drive working from the rear wheel. It can't work on the early models where the speedo drive is off the gearbox.
The 5 speed cluster fits the cases, its just that I have shortened the layshaft, this was where the early speedo drive was attached to. As you said you can use a bicycle speedo and just blank off the casing.
In answer to the first question, hopefully the first batch will be ready by end of this month. Running a little later than first projected but that's how proto stuff goes. While we've not encountered any major issues, were trying to concentrate ensuring its right rather than fast and flawed.
In answer to Irish Swede. There will only be one cam plate, to do a reverse cam plate is a whole different ball game. If you want to change the shift pattern there are a few more simpler way to achieve that rather than change the cam plate and all that would entail.