Marston Sunbeam Flat Tank models BT gearbox components with clutch bridge

Marston Sunbeam Flat Tank models BT gearbox components with clutch bridge


1927 Light Weight (L/W  is on the box) Marston Sunbeam Flat Tank models BT gearbox components including gears, mainshaft, some bearings, selector and clutch bridge.

It’s a narrow box, with two studs. I understand there are two versions of the BT box regarding width. More specifically, I understand it is to do with the length of the main shaft.  Please make sure this is the width that you need. 

Rather than list each component, please study the images. The gears are used, but appear serviceable.

This collection of parts could be the start of a rebuild for a spare transmission for your Sunbeam flat tank model. Or, you may need just some of the parts. Either way, they are for sale as a collection of parts.

From a little research in my Sunbeam book, the box might suit:

  • TT80 347cc. CR gears are listed as an option.
  • Model 6 used a Medium BT gearbox. The M5 Light Tourist apparently had an AT box.
  • Possibly others.
  • It might suit the TT90 500cc 1929-33. Although I am led to believe that this model might have a wider box. CR gears are listed as an option.

If you have any doubts, please see trusted advice. If you don’t know anyone who can help, please try the Marston Sunbeam Club

Condition of the Marston Sunbeam Flat Tank models BT gearbox components.

Things like mounts and facings are good although one mount has been repaired. I have shown this in the images. You get the parts as shown in the images and the casings / cover look decent. The internal selector and external lever are fine. The teeth on the gears that are shown are fine. The threads on the studs are fine and the keyway looks fine too.

Bottom line. This is a collection of parts for a Marston Sunbeam Flat Tank models BT gearbox and is a good basis to begin a spare gearbox build up.


Other Marston Sunbeam Sidevalve Flat Tank models gearboxes and parts for sale

I still have a few Sunbeam parts available including another gearbox case. Please go to the Sunbeam parts page and see what’s available.


Buyer notes for the Marston Sunbeam Flat Tank models BT gearbox

Shipping is charged ON TOP of the price for the item. There are too many variables to include shipping in the checkout, so please contact me before you buy and I will give you a shipping price.

I usually ship to most destinations.

International shipping available. Let me know where you are and I will send you a price for shipping with tracking

Combined shipping available. 

Viewing: Please come and check it over before you buy. It is at PE28, near St Ives in Cambridgeshire.

Collection: If you don’t want it shipped, I have plenty of space. If you can’t collect for a while, it’s not a problem. However, I will need to be paid very soon after the sale. Thanks.

Payment: Good old fashioned money on collection is preferred. I can accept payment through PayPal or by bank transfer as well. I can accept EUROS. Please ask. 

Import Taxes: Please note that IMPORT DUTIES are not something I can control. If you are buying from outside the UK, there is a chance that you will have to pay import taxes. Import taxes vary from country to country. If there are charges to pay, it is the buyer’s responsibility to research the cost and pay the duties. The price that you see on my advert is for the item and not the item plus whatever taxes might be due.


SKU: *0624-*007 - Need Help? Contact Us Leave Feedback

Tags: , , ,