The Pennsylvania State Police barracks all used to have old Onan CCK 4 pole generators that were built like tanks. Only good for around 3800 watts continuous but they could run for weeks if needed. Because they only ran at 1800 rpm, they were relatively quiet and easy on propane.
If your only getting 3800 watts out of it then there is something wrong with it.
A CCK-5 is exactly the same as the 4 or 3 just a slightly different generator head and some tuning.
the MCCk-6 is the same rolling assembly as the CCK-B tractor, just water cooled ( higher compression heads as well ).
Above 5000 watts cooling becomes an issue in the air cooled units.
Also never let a cop touch a generator ( or care for it unsupervised in any way ), just saying you will be sorry
If you look close there are two different heads on the CCK.
Most use the 5:1 head so it will burn 80 octane and its tuned to the generator its bolted too.
This is to prevent you from over loading it.
if you put the CCK-B head on an LK you turn a 2500 watt unit into a 3000 watt unit but its hell on the generator to pull that much extra power.
Not a factory authorize modification...
( LK is one half of a CCK )
For proper operation on LPG the timing needs to be adjusted and the governor tuned.
The set needs a competent technician to set it up.
People monkey with the vacuum booster because they don't understand it.
A properly tuned CCK will pull 4000 watts on propane.
Its factory spec as a true tri fuel engine
Kohlers are not. ( higher compression more general purpose engine the K series )
They require de-rating.
The 4000 watt Kohlers I posted video of are 34 cubic inch singles at 1800 rpm.
The CCK-4 is 50 cubic inches at 1800 rpm ( thats a lot of reserve power they are de-tuned a little for this application to make them reliable and still have reserve power for heavy lloads like AC units or motor loads )