It he over 70 though ?AM...moped
A ...motorbike.
B1...light vehicle quad bike.
B...
2 categories
If test passed before 1st Jan 1997 allowed to drive a vehicle and trailer combination up to 8250 kg
If test passed after Jan 1st 1997
You can drive vehicles up to 3500 kg
BE ...you can drive a vehicle with a NAM of 3500 kg with a trailer.
For a C1 you can drive a vehicle between 3500 and 7500 kg .
You need the C1 for a MH that's has a MAM over over 3500 kgs ,I don't think yours has ,it's just overweight.