I have a honda 3813 that I rescued from being stored under a satellite dish in a junk yard for the last 20 years suprizingly the engine was not seized. Iwent to work replaced timing belt, starter water pump plugs air filter carburetor paint adjusted valves. It now runs great except for 1 thing after mowing for 15 minutes like clockwork the engine speeds up to the point of being scary fast , like the governor stops working , any of you honda guys ever hear of this problem or any ideas would be very helpful. Thanks!
I had the same thing happen to me. All the sunken it revved up like crazy while I was mowing. I shut it down immediately. It was smoking from the engine compartment. After it cooled I checked the fluids. Oil was a little low and same with antifreeze. Topped them off and fired her back up. Mowed fine for about 5 minutes then began to run somewhat rough. I just it down for the day and returned to it the next day. I tried to start it a the engine seen to be locked up. The starter would not turn the engine and the fan only moved about an 1/8". Sprayed some PB blaster in the spark plug holes in hopes to assist in freeing the pistons.
I suspected that the heat caused the issue or the PTO clutch blew apart while mowing. I bought a replacement PTO clutch. Tore the whole thing down. I used the fan bolt to turn the shaft with a socket wrench. It sounded like someone chewing on marbles. However, it was freed up pretty quickly and soon became effortless to turn. I continued with the PTO clutch replacement and put it all back together. New plugs, oil, filter, air filter and coolant.
Before hooking up the hood and mower belt, I turn the key and it fired right up. I decided to take it for a test drive and drove it about 1000 feet down the street. Ran fine and then all of the sudden, it began to run rough again and but the time I throttled down it stalled out and engine stopped quickly as if it froze up again. Frustrated, I begand searching the web for insight. In the process, I located a super clean 3813 for sale relatively cheap. So I ended up buying it and swapping out the mower deck and bagger from my original. I never did figure out what happened. I suspect an oil pump failure or something.
Part 2: the back up mower was much cleaner than my original. It ran flawlessly for a whole summer. In the fall, cold day about 35 degrees or so, I decided to put the battery back in her for some leaf cleanup. When I installed the battery, the connection must have been poor because it had no power. I found this odd, but cranked down the wires to the terminal and it started. Later, I was pulling my lawn sweeper and it started to run weird. Given my previous experiences, I shut it down right away and let it cool down. Did not appear to be super hot, but it was a cold day. The next day, I tried to start it and it started and ran rough then stalled. Every attempt since then, I only get a hard click of the starter engaging with the flywheel but it only turn the engine about a 1/8", just like the first mower.
After peeking around some, I looked at the mounts from the PTO clutch and I see that one has a crack but it appears to be functioning correctly.
Now that spring has arrived, it has me back on the hunt to figure this out. I think the problem is the same with both engines, but not sure.
I saw this post and figured I would start here given its relevance. Any help or direction would be greatly appreciated!