Honda GX390 pop from exhaust


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Old 08-01-15, 08:54 AM
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Honda GX390 pop from exhaust

So this GX390in pressure washer I bought used seems to run just fine. Starts on first pull and runs nice and smooth. Today I replaced the pump and used it for about 20 min and I may need to give it another check but my question is...

What RPM should it be running at under full load? I may check the valve clearance and what should the gaps be? When I shut it down there was a single pop from the exhaust which is what made me want to tear into it.

Anything else that comes to mind please let me know, this is my first GX 390.
 
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Old 08-01-15, 11:40 AM
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It's probably the best common small engine on the market. The single pop is very common with the GX engines... nothing to be concerned about. Valve clearances should be around .006" intake and .008" exhaust at TDC. The rpm under a load is hard to say because full load varies. Full no-load rpm is usually around 3200 or so.
 
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Old 08-01-15, 05:25 PM
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Sounds good, I will check the valves just so I know they are within spec as I don't know the hours on the engine. Does this engine have compression release? I thought about verifying compression also.
 
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Old 08-01-15, 10:34 PM
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I don't recall for sure, but I don't think they have compression release. If it's not smoking, it probably has good compression.
 
 

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