ASC gearbox issues all advice greatly appreciated

[PaulieK]

Hi All
The gearbox of my bike is stamped ASC2, somebody much wiser told me that the 2 means needle roller bearing mainshaft? it has been off the bike (62 spitfire scrambler) for long time, now in the process of restoration, it will click up in to 1st gear but thats it, so decided to have a look and see whats going on.
No 1
With the pinions and shafts exposed, the first thing I see is the E sliding gear on the mainshaft (22T) is badly worn where it engages with the selector fork also the selector fork is all chewed up (see pics)
No 2
The E sliding pinion has not being engaging fully with the G pinion on the mainshaft, as far as I can tell? the G pinion has 14T and is machined or brazed on to the shaft, not pressed like G pinion 24-4217 16T.
 According to a very helpful BSA gearbox chart I saw on one of the forums, I think the mainshaft/pinion is part No 67-3313 which should be correct? the A pinion (25T) and C pinion (19T) both seem to be fine ,no damage/wear.
No 3
The bearings are the ball journal type on the drive side and on the kickstart side? I  think part No's 24-4065 and 24-4217, no needle rollers?
No 4
The layshaft appears to have the correct pinions in place, B (18T) D (24T) F (21T) and H (29T)
but the end of the shaft that goes in to the kickstart side inner cover bronze bush has some grooves on it ,which also appear to be on the bush face (see pics)
This is all fairly new to me and am learning as I go along, so all advice greatly appreciated.
Thanks
Paul

[JulianS]

Not seen an ASC2 gearbox before.

Needle roller boxes are marked T for layshaft.  T2 means layshaft needle rollers plus a needle roller inner bearing in the sleeve (A) gear. So I dont think your box is a needle roller one.

This is the only comprehensive gearbox chart I have.

You are correct the 14 tooth G gear is machined in one part with the shaft.

Your H gear may have a part number stamped on it. The H for a needle roller box has a slightly smaller thrust flange to match the diameter of the thrust washer. The H for the bushed box has thrust flange diameter to match the bush flange.

[PaulieK]

OK thanks for the info JulianS, thats the chart that I had come across, I will check the H pinion.
Thanks
Paul

[Beeza]

This may not be applicable to your problem, but it’s a couple things I found out recently, so I should share in case it cures your woes.
There are a few variations of main shafts and lay shafts, I can’t properly recall which was the ones in the conversation, but I’m sure it’s the main, there’s a different length of the gear splines from RRT2 to STD, sure there are more differences but the RR splines go a bit farther to accommodate the gears, so when one goes mixing and matching check those spline lengths.
The other one is the speedo drive gearing, the sports gear boxes have a larger gear on the layshaft and yep a smaller speedo drive gear, ask me how I know, (if anyone has a strangely smaller speedo drive pinion, the one that pushes up to the layshaft end pinion, it is needed here).
All these years and I still find little differences.
Thomas

[JulianS]

The RRT2 mainshaft fits an A gear with an outer bush and inner needle roller, it has a slightly larger diameter at A gear inner end where it fits the needle roller, this section has no oil scroll, the outer part where the bush fits has oil scrolling. This means a needle roller mainshaft does not fit an A gear with 2 bushes. You can see what I mean in the photo. The difference is only a few thou.

[PaulieK]

Hi Julian
Just checked ,no marking on the H gear and the mainshaft has scrolling along it ,but it does have the machined 14T G gear attached? see pics of casing markings.

[berger]

it seems to be a scrambles gearbox with the correct mainshaft ignore the A but SC is scrambles

[JulianS]

The long splines were 2 inches and as far as I can see were found on part 67 3315 used on the SC and SCT scrambles box and part 42 3156 the SC T2 (1957 Spitfire) scrambles box.

The photo shows 67 3315 top and a standard box shaft with 1 7/8 inch splines underneath. The scrambles shaft works in the STDT box I know because it is fitted in mine. I don't know if it works the other way around.

I read the leading A on this box (and the A on the ARRT box on the listing) as meaning "American".

If you look at the pinions used on the ASC then the 4 used on the clutch side are from the SC scrambles box and the 4 pinions nearest the inner cover plus the mainshaft are all from the "TRI"  trials box.

[chaterlea25]

Hi Paulie,
As you are Irish, and getting parts imported has become fraught with problems
I can offer you at least a selector fork and probably help with worn bush repairs
Is the damaged gear common to other sets of ratios?
Where are you in Ireland?

John

[PaulieK]

He,llo John
Thank you very much for your kind offer, you'r right ,since brexit it has become a nightmare to get even the simplest of things for bikes, I'm in munster , how do I go about sending you a PM?
Paul

[PaulieK]

The splines on the mainshaft that I have are the long type, they are 2 inches  in length (see pic)
 I think the mainshaft/pinion is part No 67-3313, according to Julian's chart that shaft has a 14T G pinion the same as mine and not the 16T?
On the chart follow the bottom column across  from ASC and it shows that mainshaft part number?

[chaterlea25]

Hi Paulie,
If you tap on my user name in the replies above a box will appear with an option to send a pm
There are detailed instructions on sending messages on the home page somewhere ?
I live about 10 miles from Cork City

John