CONVERT STD BOX TO RRT2 GEARING

[Chrisf1]

Hi again everyone I am getting ready for pleasant riding weather and find myself drawn to a RRT2 box for my baby. Upon investigation the pocket will not allow outright purchase so I would like to know the differences between STD A10 and RRT2 apart from the obvious, reverse cam plate, Torrington bearings, and the gearing. I suppose what I am saying is can I convert my STD box to RRT2 gearing and if so what do I need and what is the best way to go about it. Many thanks Chris.

[trevinoz]

I would think that it would be cheaper to buy a box than getting all the parts and having the machining done.
The question is, why? The RRT2 box is not road friendly.
  Trev.

[Chrisf1]

Nether am I but I live in the country and pretty much choose the roads I ride on, I suppose its because when I was a kid that was the ultimate mod for a beezer, no one could afford one from the factory so we only wished and never got. Even today I still cant afford it but I want to try it any suggestions welcomed. Thanks Chris

[Chrisf1]

I would like to add I am not concerned about the bearings , cam plate, etc with the mileage I do it will not concern me it is the gearing effect I am after I am running a 19T g/box 22T engine sprockets. Thanks again Chris

[dpaddock]

You'll need to ensure the mainshaft is the 67-3131 variant. The standard A7-A10 mainshaft is 67-3330.
Also, replace the bushed layshaft (42-3019) with the "T" (needle bearing) variant, 42-3094.
     David

[A10Boy]

I have been looking at this thread for several days and am struggling whether to say this or not. but can I make a suggestion without being shot at ?

Could I respectfully suggest that before you make this alteration, you ask members here of their thoughts or experiences of using an RRT2 on the road, and get some opinions.

Myself, I cant help but feel that after spending a lot of time and money, and once the novelty has worn off you will be disappointed, and you will miss the flexibility of STD gears.

I don't want to offend, but you know, we are all mates here.

 

[Chrisf1]

Well from the reactions of various people and your good selves I am now doubting the wisdom of this venture but I would dearly like to make the gearing taller I seem to be spending a lot more time changing gear than I remember from the early seventies, maybe i could try upping my engine sprocket to 23T any opinions . Many thanks Chris

[groily]

Big difference between upping the final drive ratio by changing one or other sprocket, and changing the ratios on individual gears . . . not quite sure what you're aiming for here Chris!

I don't know how many crank- or final drive-teeth one of these engines will comfortably pull in top, but received wisdom is that standard top gear is good, mostly. However, I've upped my final drive sprocket by one tooth on my A10, because I happen to live in the back of beyond and it's nice to cruise along at stress-free rpm when acceleration isn't the be-all-and-end-all. With rear sets you can probably put anything on the gearbox (you can't with the standard foot rests, that's for sure) while changing the crankshaft sprocket is the other, more expensive, option. An extra tooth on the final drive sprocket makes main road cruising at 65-70mph relatively relaxed, but motorways are still a slow-lane business these days.
 
However, if I have a complaint about the STD BSA box it's not top, it's second. It's too low. OK in traffic etc, but for me, too big a gap up and down to third. Changing sprockets obviously can't help there. An RRT2 cluster requires a lot of clutch slip in first, as I recall, and that's not great either. Not to mention the other changes that go with. I just live with what I think is too low a second gear for a country bumpkin.

A 5-speed (if money no object?)?

[trevinoz]

Chris, I think if you up the gearing, you will be spending even more time changing gears.
I leave mine as they came from the factory, the bikes will pull away from less than 20 MPH in top gear and are very responsive overtaking at high speeds without changing down. The engine revs are no worry as I have my engines dynamically balanced.
But in the end it is individual choice.
  Trev.

[olev]

Trevinoz,
I notice you have your engines dynamically balanced and wonder if you have time to tell me a bit about this.
I assume the motor is balanced to a rev range and the balance factor is something you end up with rather than a % you aim for?
I am currently rebuilding a 52 star twin with the guts of the motor spread all over the place. The intention is to spend some time and money on the bottom end and a dynamic balance is a distinct possibility.
so, what rev range does a dynamic balance cover and what will the 'black artist' need to know?
It will be a problem to give him a rev range as I've never ridden the thing or any A7 for that matter.
The bike is being built for my wife so it will probably have the ring revved off it and thrashed to within an inch of its life. (thats how she treats me anyway)
any info you have on the practical realities would be much appreciated. (a name would be good, too)
cheers 

[trevinoz]

Olev,
        I hand the works over to the engineering bloke and tell him the balance factor required.
According to Eddie Dow, the A engines were balanced to 54% for road work and 60% for racing.
It's vital that the balancer knows what he is doing.
I have a '55 Flash  and '66 Atlas on the road at the moment and both are very smooth. The vibes are not completely eliminated but are acceptable. I can see objects in the mirror now.
The cranks come back with holes all over the place, even in the counter weights.
The Atlas is so good that a friend with a 650 SS, after riding it, took his engine out and had it balanced.
H.B. Sales in Newcastle does my work, in fact they were the only engine reconditioners locally willing to tackle the job.
Another friend does his own statically and gets acceptable results but he only removes metal from the centre line of the flywheel and not from exactly where it needs to be taken.
Mate, I would talk to your local engine shops about balancing and see if they are willing, but get an estimate of cost.
It's been a while since I have had any done, the last, if I remember correctly, cost $100 - $120. It is all time costed.
If you don't want to go to the expense of having the professionals do the job, you could do half a job yourself.
Weigh the little ends of your rods and make the same weight. Then the big ends and the piston assemblies.
The Star Twin should be a real nice bike.
By the way, my wife says "you should be so lucky."
  Trev.