The Gunson Gastester is a Digital Exhaust CO Analyser with Pulse Pump. Classics first used after August 1, 1975 get their exhausts probed at MoT time. If the CO reading is above 4.5 per cent, the vehicle will fail the test (3.5 per cent for cars first used between August 1, 1986 - July 31, 1992). Hook up this Gastester at home and you can check and tune your engine accordingly. Accurate to within half a per cent, the Gastester can save you money on petrol, too. Gunson Digital Gastester may be used on motorcycles and other engines including single cylinder engines.