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Chet Drake

Hot exhaust pipe

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I have a 321as engine.It recently has been back firing when trying to start.When I get it started,exhaust get extremely hot and i also hear a slight knock.It is not a steady knock.almost sounds like something is hitting inside the engine.This has happened before and all of a sudden it stopped and ran great.I am afraid to run it to long due to the heat.Any ideas?

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Could be an exhaust valve issue.  Not seating correctly.  Also might be related to the ACR (automatic compression release) it pops up the exhaust valve briefly during the compression stroke.  it is only supposed to work at cranking speed maybe yours is stuck???

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:WRS:        You may have a carbon buildup in the cylinder and a chunk of carbon is preventing the exhaust valve from closing fully. This manual should be helpful.

Kohler K-Series SM TP-2379 LR.pdf

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I would think carbon too. The knocking can also be premature ignition caused by the carbon acting as "spark plug". I have seen that once before.

 

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:text-welcomeconfetti: to the :rs: Chet.      Looks like you have some good advice above.      I know where Goldsboro, Pa is.  Where is Goulsdboro, Pa?

Edited by Ed Kennell
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What type of engine is that? I had a knock in mine.(Single Kohler) It would make the muffler get really hot. It was the timing. I had set it to standard which did not work. I had to use a meter and the mark on the fly wheel to set it right. I think it was around 14mm. Since my timing was off it would not burn all the fuel plus heat up the muffler. So when I shut it off it back fired about a second after I turned the key off. If it is like mine search Kohler knock.

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Sounds great.I some good places to start.It is a Kohler 14 horse.Love the tractor and use it to move snow.

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On 12/5/2017 at 11:42 AM, obone said:

What type of engine is that? I had a knock in mine.(Single Kohler) It would make the muffler get really hot. It was the timing. I had set it to standard which did not work. I had to use a meter and the mark on the fly wheel to set it right. I think it was around 14mm. Since my timing was off it would not burn all the fuel plus heat up the muffler. So when I shut it off it back fired about a second after I turned the key off. If it is like mine search Kohler knock.

I didn't think it was timing because it seems to have occurred before and cleared up, but worth looking at too. Here is information on timing a Kohler.

Kohler static_timing.pdf

Edited by 953 nut
fat finger spelling

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Sounds like its time to pull the head and decarbon the head, top of the piston and inspect the valves and valve seats for build up.  If the engine is getting a bit tired, or the carb isnt up to spec, she might be getting really carboned up and this is causing the exhaust valve to stick.  Sticking exhaust valves are a common problem on aging engines.  A bit of marvel mystery oil in the gas helps but the real fix is to overhaul the engine and get it back to factory specs.  This includes reaming the valve guides to remove the carbon that gets down in them, espically the exhaust side.   

 

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