Gearbox removal, does the engine have to come out?

[berger]

4000rpm at 55mph something wrong with the rev counter mine is doing 80mph at 4000rpm

[chaterlea25]

Hi gearbox

Could be the rev counter is out or the speedo.

Agreed, one or the other needs attention unless the clutch was slipping and assuming the bike was in top gear?

I tried a 24 tooth with the same tooth counts as your bike, it was OK one up on main roads but lost out on hills where the 23 tooth would romp up accelerating as you go

John

[KiwiGF]

Yep speedo or rev counter is way out, very roughly the A10 should be geared for around 6500 at 100mph, so 4000 ish at 60mph. There are spreadsheets on this forum with the various gearing calculations.

The gearbox has a ratio of 1:1 in top gear, which cannot be altered “by design” (the clutch/mainshaft is “locked” to the sleeve gear/ front sprocket in top, so 1:1) so that won’t be a solution, or source of a gearing issue.

[Gearbox]

Thank you again good people. Lots of good info there. The gearbox is in now, but the g/box sprocket is well worn. Ordered one from Monty's classics as he was the only one that had them in stock. While its apart, I have ordered an SRM gearbox nut and clutch pressure plate. It already has the SRM drive shaft nut. 23 tooth engine sprocket will stay, (thanks Charterlea25)
Looks like progress has stopped till bits appear. Will have a look at other bits after a road test with the new gearbox.
Old unit is an RRT2 with standard 2nd and 3rd gears and correct 1st and top as I was told. Standard shafts and the relative bearing locations rebushed. Again something odd as I could easily pull away in 1st without having to slip the clutch.
That will have to come apart so I can see what is really in there

[Gearbox]

Some more slow progress. Gearbox sprocket appeared, but I had not appreciated that there were two widths. My rolling chassis is a 57 Gold Star and it uses 1/4 inch sprockets etc unlike the later 3/8 inch items. Anyway, gearbox in, clutch refitted and SRM pressure plate. Clutch was still pretty heavy, but reliased that the spring cups were the short ones, so replaced these with the correct ones for a 5 plate clutch and now have a very light clutch. Need to fit the kickstart and the primary cover before a roadtest.
Looked into the old gearbox and discovered the teeth on the various gears give standard ratios.
See how it all works in the near future.
Thanks again for all the good advice

[Gearbox]

Final update, Had it out yesterday for a quick test. Gearbox is really good, much better ratios than standard. Great bike to ride now.  Still shows 50 at about 4000, but the rev counter no longer returns to zero and it tickes over at an indicated 1500 rpm. Even to my ears, thats not right.  Looking at the gear calculator, I should be pulling about 70 at 4K, so may have to get the rev counter sorted over the winter.
Don't suppose this is common and there is a simple fix. Have to do a bit of trawling on the site.
Thanks again to all that offered advice

[1959superocket]

Has anyone managed to remove the selector shaft grub screw with box and primary drive in frame. if so please share how you managed to do it.

[RichardL]

I bet "Gearbox" is not your real name. My real name is "Sludge Trap."

Regards, ST

[muskrat]

G'day 59SR.
I've done it on a plunger but should be the same as a s/a.
Drain fluids, lay bike on it's side, remove screw.
If your removing some of the innards (mainshaft will stay put) best lay on the left side, a bit harder to get the screw but easier to get the innards out.
What you planing on doing?
Cheers

[chaterlea25]

Hi All,
I think the screw is in line with the gearbox plate on the S/A bikes so very little room there
Anyway I have not succeeded in removing one with the box in the frame 

John

[berger]

if the screw has never been out it has a factory crimping in the casing to stop it coming out, if it has been out it might have a punch mark in the casing to stop it coming out and as chaterlea25 says i agree it is nigh on impossible to access .

[muskrat]

G'day 59SR.
There you go mate. So box out.
Cheers

[1959superocket]

Thanks All,

I snapped the return spring on a ride and could not use all the box.

On strip down found 2 dogs and these are from the 6 dogs on part number 31-3198 Layshaft Sliding which you can see but cant remove unless you can take the selector shaft out secured by a grub screw which may or may not be peened over.

Tried with small right angled screw driver but nigh impossible to get at and I think you would need to remove the primary to get at it easier.

Decided to run with 4 dogs and new spring to see how it goes if no good possibly time for a 5 speed Nova if it has to come out.

Best Regards

[Slymo]

Has anyone managed to remove the selector shaft grub screw with box and primary drive in frame. if so please share how you managed to do it.

Yes you can climb underneath with a flat blade screw driver bit, the 6mm hex type that fit into a magnetic handle and a 6mm spanner. I know this because I forgot to do mine up and discovered that the selector shaft was attempting an unnatural liaison with the main chain. Got it done up tight and sealed the hole with a bit of silicon sealant to discourage further adventures.

[jjbsa]

Re the pesky selector rod grubscrew, when assembling the gearbox you can instead use a short 1/4 Whitworh Allen screw and locknut in place of the grub screw.  That is accessable and can be slackened off to allow the rod to be removed with the gearbox in place in the bike.  The Goldie racers used to do that.  It allows the box to be stripped while in the bike,
Jon