PRE MOT CHECKS
Avoiding MOT Failure
The mudguard is not a tested item, as part of the MOT test. Its condition size and position would have no bearing on the test, unless a mudguard, if fitted, adversely affected the rotation of the front wheel. They should not constitute any 'dangerous parts', e.g. sharp protruding edges, etc, that may cause injury to a pedestrian in a collision.
HOWEVER the MOT test is only a periodic safety check to identify worn or defective parts, it doesn't check whether the bike is actually legal to ride on the road.
Motorcycle mudguard requirements are contained in Regulation 63 of "The Road Vehicles (Construction and Use) Regulations 1986 (SI 1986/1078)" as amended. It states that, motorcycles are required to have mudguards fitted which catch, so far as practicable, mud or water thrown up by the rotation of its wheels.
Summary: If you have no mudguards it will not affect your MOT. If you do have mudguards they must not obsctruct the rotation of the wheel or be deemed hazardous. Mudguards are not required for an MOT but ARE required by law.
Regulation 63 of "The Road Vehicles (Construction and Use) Regulations 1986 (SI 1986/1078)
Provides for the fitting of wings or mudguards to vehicles to prevent mud or water being thrown up by the wheels or tracks.
63(1) This regulation applies to:
(a) invalid carriages;
(b) heavy motor cars, motor cars and motor cycles, not being agricultural motor vehicles or pedestrian controlled vehicles;
(c) agricultural motor vehicles driven at more than 20 mph; and
(d) trailers, unless exempted by paragraph
63(2) Every vehicle to which this regulation applies shall be equipped with wings or other similar fittings to catch, so far as practicable, mud or water thrown up by the rotation of its wheels or tracks.