Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board BSA A65 5 speed gearboxes

Hi Allan

While I can do 74.5mm bore and whatever height you want. I had the pattern made more like the Devimead/SRM its also 6 fin as well, this I did to make it simpler to make and should also give a better quality casting from the mould.
Once I have had the first on machined I'll take some photos and post them. In the mean time I'll also carry out a pull test with a 3/8" BSF 20TPI thread.

regards

John

I must say I am with Allan on the fin shape.

My personal view is that the primary product should be as standard as possible, thereby making use of standard pistons. This is because there is a premium these days on things being kept standard, or at least looking standard.

As for specials, well it would be useful to have a 'upgrade' to something that could be a 700-750cc conversion and if this could be accomplished with a standard looking barrel, I am confident that the market would be greater too.

As ever, just my thoughts....

I would be interested at that price point. I would love my A65 (1970 pre-OIF) to be a 750cc five gear motorcycle.

As Allan says in his first post, the price point for the 5 speed gearbox will be in the region of GBP1,500 or approx. USD2,300. You then need to add on delivery, gaskets, seals, oil plus all the bits you were intending to do but hadn't yet got round to doing etc etc. And that price assumes there are 25 people prepared to pay a deposit to secure this special order.

That being said, Quaife has indicated that the gearbox is a straightforward swap for the existing 4 speed and it is an existing design that has already been used successfully in a BSA A65.

Hi Allan you can now make that two 5 speed gearboxes, lets get it done.

Hi Allen, I did not get a cost for the compete gearbox, just cutting the gears. $2300 sounds high but since Quaife does not sell direct you have to pay their cost and profit and their dealer's profit.
I have not had time to work on this due to regular work and some new triple parts that I need to finish. It will get done as I need a 5 speed for the A74XS and I am too cheap to pay that much.

I am all for people buying and doing whatever they want to their bike, but at US and Australian dollars this would nearly run out at $3000 and unless racing I'm wondering if I would feel satisfied. I live in a very hilly winding area and the 5 speed triumph do do better, but the A65 does manage quite well (1 whole coffee ahead of HD).
I hope you get the 25 needed and look forward to hearing positive results.

HI John
I would be interested in two sets of cylinders when you get them machined. We can get them Nikasil lined here in the states saving you the bother of doing that part. We also would want coarse threads in the cylinder as I do not like fine threads in aluminum. The bore size we are after is 76 mm but if you had them at 75 we can take care of the oversize here.
Ed

Hi Ed

Thank you for the interest. I agree with you comment on fine threads in aluminum and have done pull tests on 5/16" 18 TPI UNC which I plan to use on the 79mm bore and have taken the torque up to 40 lbs/ft and thread in the aluminum was still good, I'm only looking 25 lbs/ft.
No issue with you doing the final bore and coating there as it will simplify the process.
My e-mail address is [email protected] where we can discuss in more detail.

regards

John

John, please excuse my 3/8BSF comment from earlier. I wasn't thinking properly. As per Ed a coarser thread would be better in Alu', my concern has been the bolts themselves, as I had found (in my case) that the original bolts didn't carry enough thread and buggered up the thread in the barrel, Since then I have made my own and never ran into that issue. On a 650 barrel the 3/8 shank is still preferable. You have done very well with taking the 5/16" bolt upto 40 lbs/ft and it not cause damage, 25 lbs/ft is correct for that size of bolt anyway.



Gearbox info.

I have created a chart on Excell, it isn't a fancy one where you can plump your own figures in and it all works out for you etc. This is just a basic table.

(i'll upload it later)

From my recconing, and this should suit the guys with 21/47 gearing and certainly won't harm anyone with standard 20/47 gearing would be the 2.6:1 first gear ratio.

Running a taller gear set like myself will be able to live with it not being lower than that.

The 2.6:1 ratio is on a separate list.

For information, this is my first contrubution to this forum.
I recently purchased a second-hand Quaife 5-speed gearbox with road ratios for my 1971 A65FS. I subsequenly had it serviced and checked by the engineer at Quaife, (in Kent, in south-east England), and I replaced a couple of worn gears.
I live in west London, so I asked nearby Richard at P&M motorcyles to replace and fir the new gearbox, unfortunately, he had too much work on earlier this year and he suggested taking the work to Geoff at SRM, (in west Wales), note that I had used SRM previously; 4 years ago for a complete engine rebuild service.
In all my discusssions and dealings, all three companies, (Quaife, P&M and SRM), were reasonable, patient, understanding and realsitic in their advice and in dealing with my expectations. I would recommend any of the three companies to anyone.
Meanwhile, after SRM's fitting of the gearbox, I rode the bike back to west London and it runs well with a slick gearbox in all five gears.
I can advise further details should anyone need any further info.
Regards,

Dmb, thankyou for your input. Please feel free to share all your experiences with the product, what may seem trivial to you can vital information to someone else.

Please tell us what gear set up your running as in primary and final drive. I know some 71 firebirds came with 18:47 on the final drive which is really low.

Richard @ P&M mentioned to me about someone who purchased a box etc, I think it might have been your good self.

Thankyou for joining us.

One personal question I have is about the length of travel on the lever with the 5 speed. A std 4 speed box has a nice amount of travel, I have found the 5 speed trident and 4 speed Bonneville box to have a shorter range of travel.

Allan are you sure of those 5 speed ratios for the A65? The 4-5th gap seems quite big. I like the std 3-4th spacing because if you spin the things to 7,500 going into top is 6,551 and changing at almost whatever place lower in the power spread it tends to drop you into top with it still in power. EG if you have 50hp at 7000 45 at 7500 and 46 at 6500 and your 4th gear needs 45hp to hold its max speed, changing into top on the 5speed becomes 6,073 where you might only have 40hp and its dead, and not going to go faster, actually going to slow, where as if it was at 6,551 like the std 3-4th you might have 47HP giving 2hp to pick up speed and maybe reach 7,000, and the only way to do that with the 5speed is run 4th over 8,000. In the lower gears it makes proportionally less difference because it requires less HP to maintain lower speeds so some will be left to accellerate with. In my idea of the ideal gearbox the ratios would get closer the higher the gear so it keeps the motor right in its peak power zone. On the road the ratios might be quite fine and top like an overdrive, but racers and performance guys might like a closer 4-5th.

I know what you mean Mark, 1.2**** is a far bigger jump than the original 1.144:1

The whole thing seems to have fallen flat, and to be frank I hav too much work on at the moment that I was getting to the point of not sleeping, so for me I'm sticking with my 4 speed and working on other fun mods.

I concentrated mainly on 1st gear as I found it to be a little low, but as I can't post my Excel file on here (and I can't remember my password for my own website to use that as a host) If you like I can email it to you. It does show the RPM's vs 10mph and 100mph and the drop in RPM.

The gear ratios of the 5 speed (ignoring 1st) can be effective depending on where you make your best torque, if its all low-to-mid range then the box as it stands will be ideal. It's been about 4 months since I rode mine (and I never dyno tested it) but it was making great power from nothing - 6000rpm, it was still pulling just as strong at 6500 RPM (although I would think the torque curve was falling off) and maxed power at 7000rpm. I could easilly afford a 2000RPM drop from 6000-4000 and it would still pull like a train (on more gentle rides I could double shift from 2nd to 4th)

Allen if you have access to one why don't you get your bike dynoed and see what its got and get a graph of the power curve? As it is at 650cc or 670 whatever it is and you could compare it to what other people are getting from a 650. And if you decide to get an alloy cyl get the big bore, because it would cost the same but probably give you more pleasure. The big bore kits need to use smaller bolts and studs so they don't distort the bores when done up, mine has no problem with the sealing. Going from 76mm bore to 79.5mm bore with mine enabled it to go from 57hp to 78HP (both with the 89mm crank) so 818cc (I think) to 883cc the power increase percentage is much more than the cc increase and I think it's because the window under the valves being bigger helps the breathing. A big bore 750 can make heaps of power though we haven't set a data logger up on it to measure an exact number.

Here's Allan's Excel file....

Calculating Optimum Gear Ratio

Cheers Two Alpha.

Mark, yes I intend to dyno the bike when its run in etc (possibly start of next year the way its going) Max HP isn't of great importance to me if I can make maximum torque in all the gears, and hopefully achieve a good top speed. I'd also like to see the change from using a head with a leaking chamber to a good head, I might even break the 7000RPM limit just by having good compression.

Allan

Check this website.
For a few quid you can purchase an excel sheet with the various formulas etc.
Save a lot of time for less than a tenner and gives you a lot of info on all the variables.

http://victorylibrary.com/TRI-5.htm

I have that Kev, the A65 one. It makes calculations for options easy.

Are these gearboxes still a possibility? I'll commit to one.

Thanks

Good grief. I keep hammering my profile. That's a '69 T150 not T160.

Here are some graphs of gear ratios - the 4 speed standard and close ratio, ratios I selected for a 5 speed and Quaife's box. It appears Quaife's 4th gear is too high making it a short gear from 3rd and large reach to 5th.

Exactly! I only concentrated on first - second gear to be changed, but the rest of the transmission doesn't lend itself to neither road work (when using taller gearing) or racing IMO

For racing its as though they don't expect anyone to get into top gear.

ummm if i rode a bike that didnt pull max rpm in top on the fastest part of the track i would sack the mechanic!iv watched over this thead and i still cant see why you would want 5 speed ? std cr boxes are great. i run a tuned hinkey bonnie and i would love just 4 or even 3 gears.

I think your missing my point wak.

I was referring to the spacing between 4th and 5th

I can make a 4 speed work really well on the street, however if someone was to lower 1st an 2nd a touch and squeeze a new 3rd in there. It would be a really sweet box.

A lot of A65 owners up the gearing, it's ideal for touring as your getting good economy and keeping the revs down, it also further defines the need for a better spaced 3rd gear in a 5 speed box.