by Skywatcher » Thu Dec 03, 2015 12:35 am
Hi Luffy
Although the crankcase halves join on the diagonal, all the bolts and alignment dowels are parallel to the crankshaft. The hardest part about getting these engines apart is separating the sealant that holds the crankcase halves together. Once you're inside, there's almost nothing to them, just the crankshaft, cam belt and governor. Everything else is up in the top of the cylinder. If one of these engines comes in on a lawn mower and has zero compression, check for a bent valve cover from hitting a tree etc. If the cover gets bent in too far, rocker can't move all the way so valve doesn't close.
With the valves being parallel to the cylinder, if a valve gets stuck, the piston just pushes it back towards the seat. If the cam gear gets out of time, you'll get a broken rocker and not a broken valve or piston. If memory serves me correctly, the cam belt is supposed to be changed every 400 hours of engine run time. I'm not sure what the life expectancy is for these engines, I've heard anything from 400 to 1,600 hours, depends who you talk to. All the best,
Sky
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