faffi Posted August 11, 2011 Report Share Posted August 11, 2011 Today, the Yamaha XT600 refused to start. It had sat still for 3 weeks, and I would usually have expected stale fuel. But using the kick starter, it felt like the engine had lost just about all compression. Bump starting in 2nd gear easily turned the rear wheel even when not sitting on the bike, instead of locking up like usual. So I checked valve clearances (OK) and decompression mechanism (detached, but made sure it hadn't moved or jammed) and found nothing amiss. Spark was good. Did a compression test and only got 7 kg per square cm (I think - at least it was 7.0 of something). Not good, but enough for an engine to run. Drained the carb, fitted everything back and got the odd puff, at least. Some pushing finally got it going and the engine sounded like normal. Doesn't seem to miss any power, either, but perhaps runs a bit smoother at low rpm than before. No undue noises, either. Only compression and oil consumption suggest something is not right. Oil consumption was zero for the first 2500 km or so after I bought the bike, then about 1500 km ago it suddenly began using oil. A lot. Like about one litre per 1000 km. My personal guess is a broken piston ring that in turn have scored the cylinder. But I'm interested in other theories. So if you have one - or several - please share them. Quote Link to comment Share on other sites More sharing options...
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