Small Engines (Lawn Mowers, etc.): 20hp Honda engine kills after 20mins of running, exhaust gases, honda engine

Question
QUESTION: I have a 20hp honda gx620 I. It is mounted in the back of a van to power a truck-mount carpet cleaning system. The engine was brand new last summer and only has about 100 hours on it!. When I first used it last summer it would kill after about 20 mins of running. When it would kill it seemed to surge up and down and eventually die completely. The problem seemed to magically go away for about 5 months! Now it is back again stronger then ever. Any help would be appreciated!


ANSWER: Lets look at the obvious here, is your oil level completely full.  Your oil switch is very sensitive to the level.  The hunting and surging you are describing may actually the engine turning on and off.

you say its on the  back of a truck? IS it on an open bed pick up or is it inside the back of a panel van?  Reicrulated exhaust gases can cause your engine to vapor lock. once it cools its apt to restart.

Does this help you at all?  If its an overheating problem.. get more air to it.  I also recommend running a fully synthetic oil in it such as Mobil 1 10W30

Let me know what you find

---------- FOLLOW-UP ----------

QUESTION: Yes Oil level is completely full, I just changed the plugs too! They were a little whitish but not bad. Yes its in the back of of van. The machine sits right by the side door of the van to draw in air. The exhaust is drilled through the bed of the van so it all goes out the bottom! I have always used sae30 in it. So I should change to 10w30?

Answer
There is a yellow wire coming out from the inside of the engine.  This is your oil sensor.  Unplug this and see if this makes the problem go away.  If it does you may have to replace the oil switch.  I'm not real crazy that this is the cause...

Your saying its in the back of a van,  What part of the country are you located in?    

Keep me updated please

You can switch to SAE 10W30, but if SAE 30 has been working for you and you have been using it religiously and changing it regularly then keep doing so.  I just gave you a suggestion for an extreme use engine.  My motto is if it works....not mess with it!