MEP-531 exhaust popping

[sigo]

Just got around to servicing a MEP-531 I picked up a little while ago; changed fluids and filters and fired it up. As usual it took some fuel bleeding and a bit of cranking to get it to run. Once it fired I starting getting quite a bit of popping and some “backfires” thru the exhaust. Any experience with this or thoughts on easy fixes before I tear into the head to check valves, check timing, and whatever else I can think of?

 

[rustystud]

Just got around to servicing a MEP-531 I picked up a little while ago; changed fluids and filters and fired it up. As usual it took some fuel bleeding and a bit of cranking to get it to run. Once it fired I starting getting quite a bit of popping and some “backfires” thru the exhaust. Any experience with this or thoughts on easy fixes before I tear into the head to check valves, check timing, and whatever else I can think of?

If someone set the valve lash incorrectly it could be causing this. Also the fuel timing could be off. These "Yanmar" engines are pretty dependable units with few mechanical problems.

 

[Guyfang]

The only time I have seen this with the yanmar engines was when the valves were out of adjustment. This is one of the few engine problem I ever saw with this engine. Normally it a good runner.

 

[sigo]

Valve adjustment is my conclusion as well. Hopefully that’s all it is. I appreciate the input.

 

[Kenny0]

Other posts are very good. Another thing may be a sticky valve.