Hi Grumpy, whats an easy way to tell the difference. This motor has got over head valves, the number I have found is 331877/0240-B5. Have had a quick look through the " operators manual" and it states that if engine backfires then you have a faulty spark plug,could this be part of the problem or is it their way of making you buy more stuff until you get peeved of and take it to a mechanic.
