uhoh7 Posted May 22, 2013 Report Share Posted May 22, 2013 Hi guys I was changing out my fan and orings, and water pump on my backcountry 300 pro, which I've shown pictures of here in the past. With the head off. I was cleaning the top of the piston and cylinder top face, when i noticed: my piston (not that old) has a tiny bit of play on a circular axis. Not up and down, not side to side. I never really have handled the piston in the cylinder like this==with this particular motion, so I am not sure if it may be normal or an indication of a rod bearing issue. TY in advance Quote Link to comment Share on other sites More sharing options...
suzuki250 Posted May 22, 2013 Report Share Posted May 22, 2013 (edited) If you can turn the piston clockwise / anticlockwise you have a bearing issue that needs further investigation (Probably the little end bearing) Edited May 22, 2013 by suzuki250 Quote Link to comment Share on other sites More sharing options...
0007 Posted May 22, 2013 Report Share Posted May 22, 2013 Not. Necessarily, if it moves a couple mm in each direction that's normal Remember that's a motion that never happens when the engine is running so it has no meaning It also has no spec to measure So....not to say you don't have motor problems but that is not how you check it Quote Link to comment Share on other sites More sharing options...
zerorev3rev4 Posted May 22, 2013 Report Share Posted May 22, 2013 As above slight rotation is normal Quote Link to comment Share on other sites More sharing options...
uhoh7 Posted May 22, 2013 Author Report Share Posted May 22, 2013 Thanks so much, the top is pretty fresh, I suspected it was normal, thought i'd chk Quote Link to comment Share on other sites More sharing options...
billyt Posted May 22, 2013 Report Share Posted May 22, 2013 (edited) If you did NOT have this circular play then you WOULD have a problem. The piston has to some what float in the cylinder head as the centre of the barrel, as it bolts down to the cases will never be deadly accurate. That is also one of the jobs of the piston rings to help seal this slight non concentric play. A little bit of play left and right at the piston pin A little bit of front to back from the con rod A little bit from the piston as it fits in the rings All this equals some play. Edited May 23, 2013 by billyt Quote Link to comment Share on other sites More sharing options...
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