# Engine Compression on Coleman Powermate 6250 ??



## MOOSETRAX (Jul 24, 2022)

Hey folks, Just got the generator carb cleaned & got it running (as it sat 2 years), it does back fire or pop randomly but runs / idles fine. Compression showed 98psi. I wonder if thats an acceptable psi for this Tecumseh 10hp engine. It does have the 220v RV plug outlet which i love to convert to Welding plug socket so i can use it for off site welding. Sorry didnt find a relative topic thread & hence posted here. Thanks in advance.


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## grizz55chev (Jul 24, 2022)

MOOSETRAX said:


> Hey folks, Just got the generator carb cleaned & got it running (as it sat 2 years), it does back fire or pop randomly but runs / idles fine. Compression showed 98psi. I wonder if thats an acceptable psi for this Tecumseh 10hp engine. It does have the 220v RV plug outlet which i love to convert to Welding plug socket so i can use it for off site welding. Sorry didnt find a relative topic thread & hence posted here. Thanks in advance.


One way to check is to load it up to 80 percent of its rated output and watch for a steady 60 hz or near , like 58 or 59 with upwards of 115 volts. Any significant drop in hz or volts means engine wear or power head problems. I watch guy on y tube named James Condon, his videos have helped me understand the inner workings and limitations of various makes and models of gens available to the general public, hope this helps.


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## MOOSETRAX (Jul 24, 2022)

grizz55chev said:


> One way to check is to load it up to 80 percent of its rated output and watch for a steady 60 hz or near , like 58 or 59 with upwards of 115 volts. Any significant drop in hz or volts means engine wear or power head problems. I watch guy on y tube named James Condon, his videos have helped me understand the inner workings and limitations of various makes and models of gens available to the general public, hope this helps.


Thanks Grizz, My dig meter showed 122v at both outlets without any draw. Will check upon load & see if there is a drop. Also upon browsing on the occasional pop sound, they say it could be the valves not being seated fully due to heat over time. I blv it can be easily fixed by filing the valve seat stem.
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" In my experience if it feels like a engine when you pull the rope then it's an engine that should start. If it can't start with spark and fuel then compression may be in question.

If it does start but becomes unstable after warming up for a few minutes, eventually stalling and feeling easier to tug on the starter rope then the valve have hobbed the seats. The valves get too long to seal when heat expands them, especially the exhaust valve. When this happens compression crashes and the engine dies out. Eventually they won't even seat well enough for predictable starting if you can nurse it along long enough.

The remedy is to grind the valve stems to restore lifter clearance. You will get to clean the head and piston top at the same time. Unless the cylinder wall has something significant going on leave it alone. Put it back together preferably with fresh gaskets and you have a good shot at the block going for decades more. Remember to torque the head bolts to spec. Many carburetors have been needlessly rebuilt chasing this since it can seem like the engine is running out of fuel.

Unless the valve spring retainers give you a hard time it should fit into a 2 hour session."
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## cookies (Jul 24, 2022)

Hrz is based on engine rpm, they must hold rpm indefinitely under full operational wattage load (not peak). Often gensets are not run long enough to really break in and are not oil changed often enough when actually used. They often sit years between usage.


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## grizz55chev (Jul 24, 2022)

MOOSETRAX said:


> Thanks Grizz, My dig meter showed 122v at both outlets without any draw. Will check upon load & see if there is a drop. Also upon browsing on the occasional pop sound, they say it could be the valves not being seated fully due to heat over time. I blv it can be easily fixed by filing the valve seat stem.
> -----
> " In my experience if it feels like a engine when you pull the rope then it's an engine that should start. If it can't start with spark and fuel then compression may be in question.
> 
> ...


Valves would be my guess on the backfire as well, some small engines have a de-comp built in where 60 psi is a normal comp reading, not sure about yours.


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