Hi Tugay, and the usual suspects are:
1. Fuel tank empty.
2. Fuel supply valve/petcock turned off.
3. Fouled spark plugs.
4. Engine flooded as a result of over use of enrichner.
5. Vacuum hose to fuel supply valve/petcock disconnected, broken, cracked, or pinched.
6. Fuel valve/petcock or filter clogged.
7. Discharged battery, loose, corroded or broken battery terminal connections especially the "NEGATIVE" cable inside the harness at both ends.
8. Loose or corroded wire connection at the coil, battery or plug between ignition sensor and module.
9. Spark plug cables in bad condition and shorting, cable connections loose, or connected to the wrong cylinders.
10. Ignition timing incorrect due to faulty ignition coil, ignition module or sensors (MAP, CMP CKP and/or BAS).
11. Sticky or damaged valve or pushrod wrong length.
12. Primary cam sprocket spline sheared or missing spacer.
13. Security alarm needs a reset.
For more information about your issue, please visit the websites below. Good luck and have a nice day.
AJS Regal Raptor DD 125 04 06 Manual Haynes