Gearbox sprocket spline

[SixFingerJack]

Hi folks, I'm trying to find a 16t sprocket for my '48 A7 rigid.
Does anyone know if the longstroke sprocket has the same size spline as the later models?
Thanks in advance.

[trevinoz]

Same spline but the early boxes don't have a seal and have a scroll on the sprocket. Later ones have a seal and no scroll.
If you can only get a plain sprocket, you will have to fit a seal.16t seems a bit small.

[SixFingerJack]

Cheers Trev, is there room to fit a seal behind the sprocket?
16T is gonna be somewhere near, hopefully, I'm running a 42T rear, with a 5.00 x 16 tyre.
Yeah, I know that'll upset the rivet counters!

[duTch]

 Geez 6FJ...that'll rev like buggery and go nowhere. ...I use the standard 19/42 and have thought to go 20... Hope that 16x5 fits OK. . Maybe just?

[SixFingerJack]

You may be right duTch, I've never ridden the bike, it arrived in boxes, and was very incomplete.
It had 18/49 gearing and a 3.50 x 18 rear tyre, maybe those weren't the standard spec.
I'm more than welcome to admit that I am well outside my area of expertise with something this old!
Both the sprockets were totally knackered, but I found a brand new 42T rear at an autojumble.
I did a quick calculation, and since you can't get a 15.4 tooth sprocket, I reckoned 16 would be near enough.
Oh well, I actually though it may be a little overgeared with the bigger rear tyre ...........

[duTch]

 Yo SixFJ, (  likely hereafter I'll just call you 'Jack,Six, or Fingers'), that's fairly much sidecar gearing-even lower, I think sidecar is normally 19/49..

 I run a Metzler Enduro2 18x4.00 on a 18WM3 rim, and it has 10mm-1/2" clearance from the chain (~52/3 Plunger), so a 5.00 may just rub a bit..
 I think the box I'm running is from a rigid...came with the sprocket with a scroll and the matching steel shroud, and the flat kickstart spring with no retaining 'through-screw'.
    I fitted a seal ok but did have a minor issue as one replacement seal has a rubber backing that mates to the bearing outer ring, and the outer rim is subsequently a bit tight for the hole, but not by much and fits ok in a couple of other later cases......as I already had another older seal presumably pre this innovation, I used that instead, with some 3-Bond, and seems to be fine
 

[SixFingerJack]

Hi duTch, thanks for the help.
You say you are using 19/42, so, as mine is a longstroke A7, it'll be a few horses down on your A10.
After some consideration, I think a good compromise would be to keep the 42t rear, and fit a 18t on the gearbox.
What do you think?
Regarding the chain/tyre clearance, I have 5mm or so, so it might rub now and again, but I won't lose any sleep over it.

[duTch]

 probably best I leave it to other Longstrokers for their points of view...

[trevinoz]

Jack,
               The seal will replace the slinger sleeve.
You will have to make a decision on your sprocket because there is no easy way to change it later.

[SixFingerJack]

Cheers Trev, I see what you mean about the seal location now.
I was thinking, that's gonna have to be a really thin seal, doh!
You're right about making a decision, too, and I have.
Going for a 18T, then if the gearing is too high, I have two choices of larger rear sprockets - 46T & 49T.