Section A1 - Engine

Starmaker or Stormer?

Do you know if you have a Starmaker or a Stormer engine?
There are many differences, and some parts do not interchange.

All Stormer engine numbers begin with A250
Starmaker engines are designated 225H with the following variants:
757D Standard Scrambles with wide fins, wide ratio gearbox and twin Amal monobloc carburetters.
490E Road racer version of 757D but with close ratio gears and a tacho drive.
494E Scrambles, but with 6v direct lighting.
826E Scrambles, with single Amal monobloc carburetter.
827E Scrambles with single Amal monobloc carburetter and 6v direct lighting.
834E Road racer with close finned cylinder and head close ratio gears, tacho drive, outrigger contact breakers, and Amal 3GP2 carburetter.
865E as 834E but with 6v direct lighting.
871E trials engine, with wide ratio gears, and Villiers S.25 carburetter, but without lighting
972E Sports roadster, with single Amal carburetter and 12v rectified lighting.
091F Special, with single Amal monobloc carburetter, but without clutch, gearbox and primary drive.
131F Trials engine with 6v direct lighting.

Visually the Starmaker and Stormer emgines look very similar, but in summary the following are the main items of difference:
1. The Stormer piston has a shorter back and has shrouded rings covering the ring pegs. The Starmaker has butted rings and a longer back.
2. The Stormer crankshaft is wider due to the big end having thrust washers either side of the crank pin, where the Starmaker crank does not have thrust washers.
3. The Stormer con-rod has a 3/8" diameter oil hole in the top, the Starmaker rod has a wide (and weaker) oil slot. (fine for trail and trials use)
4. The Stormer has reinforced engine mounting point on the crankcases.
5. The Stormer crankcases are wider inside to accept the wider crankshaft (see point 2)
6. The Stormer has reinforced ribs on the gearbox to frame mounting.
7. The Stormer has a removable cylinder liner, the Starmaker line is "cast in"
8. The Stormer may have close ratio gear ratios, the Starmaker would have had wide ratio, trials or road race gears.
9. The Stormer has a lighter and stronger magneto flywheel than a Starmaker.
10. The Stormer has different clutch friction plates to those of a Starmaker. The Starmaker plated have a riveted centre fitted to them.
11. The Stormer has a larger diameter clutch centre.
12. The Stormer has the spacing of the front chain case screws spaced closer together to give better clearance inside for the primary chain. The Starmaker inner chain case has mounting hole next to the gearbox sprocket, the Stormer does not have this hole. Therefore, they do not interchange.
13. The Stormer has a longer clutch operating pin.
14. The Stormer has an improved clutch pressure plate (not diaphragm spring)
15. The Stormer has an improved gear change quadrant.
16. The Stormer has an improved gear change cam barrel.
17. The Stormer inner magneto case has a sealing O-ring against the crankcase; the Starmaker casing does not have this O ring.
18. The Stormer does not have an exhaust gasket because the exhaust is mounted in a push- fit sleeve. The Starmaker exhaust is clamped to the cylinder and needs a gasket.