I have a 20kw 5875 model that was installed back in the summer of 2011. Initially when the unit would crank, the generator would start up right away, but further down the road, perhaps 6 months or a year, I was noticing that the unit was not starting up right away when it would crank. It was becoming a common theme where it would take towards the end of the second crank cycle, or the beginning of the third crank cycle, (cycle meaning a 10 second pause before it cranks again) for the unit to finally start up. Once it would, it runs just fine. It's the beginning stage that is creating some difficulty. If you turn the unit off after it starts running for a minute warming up, and then manually turn it on, it starts up right away instead of having a hard time.
The hard start happens every week during the exercise schedule.
I've had a certified tech come out and take a look at it, we checked gas pressure, water column, the fuel is fine coming in. I noticed a small improvement if you changed to brand new spark plugs but that would be short lived. The tech believed it was the magnetos and had those replaced but nothing really changed after the replacement. A new battery was also fitted with no change.
The unit runs on Natural Gas and has the correct pin setting on it inside the air filter.
In rare instances especially in cooler weather, the unit would over crank. We do have an oil filter warmer. The battery warmer looks to die out. The technician who does our yearly maintenance said they dont install the battery warmers anymore as it tends to overheat the battery and cause acid leaks.