This post will help you understand a bit more about the Autochoke system found on most modern Honda mowers, and on many other mower brands that use Honda engines fitted with Autochoke. There are also details about the Honda Service Bulletin (January 2014) related to Autochoke.
Background:
Engines with carburetors need a mixture of air and fuel to run. When an engine is cold, it needs less air at first, and after warming up, needs more air. A controllable restrictor or
choke plate is used to make this work on Honda engines. Other designs use a primer bulb to manually inject more fuel for starting, but either version gets the job done by temporarily changing the mixture of fuel and air.
Until recently, many Honda engines had a
manual choke built into the throttle cable and control. When you moved the throttle past the FAST position and into CHOKE, the choke plate was closed. After the engine was warmed up, you'd move the lever out of CHOKE and into FAST. This held the choke plate fully open so maximum air could flow.
However, many first-time users of mowers did not understand or realize the purpose of the choke, how to use it correctly, and this resulted in hard or no-start conditions. Further, the control cable could become bent or broken when folding the handlebars for storage, there was extra cost for the parts, exhaust emissions would be worse if the choke was used improperly, the list goes on and on, so there was a lot of good reasons to automate the choke process during engine start-up.
How Honda's Autochoke Works:
On a cold engine, a spring puts constant pressure on the CHOKE CONTROL ARM (blue) to hold the CHOKE PLATE (pink) closed. After the engine is started, heat from the engine warms up the WAX CYLINDER (yellow) causing the wax to expand, pushing the PISTON (purple) out and forcing the CHOKE CONTROL ARM into the opposite direction; the CHOKE PLATE is then opened, allowing more air to enter the engine.
When the engine is turned off and cools, the wax inside the WAX CYLINDER cools and contracts, and the SPRING pushes back on the CHOKE CONTROL ARM. The CHOKE PLATE is moved back into the closed position as the PISTON is retracted back into the WAX CYLINDER.
Common Symptoms and Issues:
If the mower is hard or impossible to start, it
could be because the Autochoke is not working. There may also be many other things that can make for hard starting, so don't be too quick to think it is the Autochoke. Clogged carburetors, stale gasoline, plugged air filters, bad spark plug, etc. can and are frequently the most common reasons for poor starting and/or running issues.
Special Note About Warm-Up:
A frequent complaint is when an engine starts, but is then shut down before being fully warmed up, and then won't restart. This typically can happen when using the mower in cooler weather. If the engine is not run for at least 3 minutes, it is possible for it to not fully warm-up, but still get warm enough to activate the Autochoke. Restart attempts may fail, since the choke plate is open but the engine is still too cold to start/run with too much air flowing. If this happens, let the engine cool off a while, so the choke plate can return to the closed position, then when you restart, be sure to let the engine run for a full 3 minutes before you attempt a shut-down and restart.
How to Inspect / Check the Autochoke:
1. When the engine is completely cold, remove the air cleaner cover and filter element. Look in the opening and confirm the choke plate is completely closed.
2. If the choke plate is open, even partially, the linkage may be sticking; skip to step 4.
3. If the choke is fully closed, start the engine and let it run for at least 3 minutes. Shut off the engine and confirm the choke plate has fully opened. Allow the engine to cool for at least 30 minutes. Re-check and confirm the choke plate has fully closed. Repeat this step; the choke plate must fully open after 3 minutes of operation, and fully close after the engine has cooled for 30 minutes. If all this checks out, the Autochoke is working properly.
4. In January 2013, Honda issued a Service Bulletin about the Autochoke. A limited number of Honda mowers may have a defective Autochoke linkage (usually binding or sticking). A mower with a defective Autochoke that is still under warranty is usually repaired at no charge when done by an authorized Honda dealer. Both the Autochoke linkage and the wax cylinder and may be replaced under warranty. It is important to note not all mowers with Autochoke have a defective part, and hard or difficult starting may be caused by other problems (dirty carburetor, clogged air filter, etc.).
Where To Find The Serial Number:
Look on the back of the mower deck:
Affected Honda Mower Models & Serial Number Range
Mower Model Name Serial Number Range
HRR216K8 MZCG-8400001~MZCG-8669999
HRR216K9 MZCG-8670001~MZCG-9100553
HRX217K3 MAGA-2069723~MAGA-2199999
HRX217K4 MAGA-2200001~MAGA-2325178
What About My Honda Engine on Brand X Mower?
Check the engine serial number on the side of the engine block; it is etched, and may be hard to see, so use a flashlilght; here are the affected GCV160 or GCV190 engines that may have a defective Autochoke.
Honda GCV160 Engines:
GJAPA-1000001~GJAPA-2295257
GJAPA-1546575~GJAPA-2295257
GJAPA-1000001~GJAPA-4630773
Honda GCV190 Engines:
GJAPA-3180269~GJAPA-4630773
GJAPA-1000001~GJAPA-7147598
If you think the Autochoke is not working properly on your Honda engine,
and it is on a non-Honda mower, warranty repairs must be done by a Honda Engine Dealer; find one using this link:
Find a Honda Engine Dealer
What To Do Next (if Autochoke is not working properly AND your 100% Honda mower is in the affected range):
Have a Honda Mower Dealer inspect and evaluate; they can confirm if the choke is defective, determine warranty status, and perform repairs. Be sure to have the dealer confirm what will or will not be covered under warranty before authorizing any work. Find a Honda Mower dealer using this link:
Find A Honda Dealer
How to Find Out if Your Honda Mower or Honda Engine is Still Under Warranty:
Three ways to find out:
a. Drop me a PM with the serial number; I can look it up for you.
b. Call your Honda dealer and ask them to find out.
c. Call Honda Customer Relations: 770-497-6400
Why didn't Honda contact me about this Service Bulletin?
For service issues that are NOT safety-related, Honda issues the Service Bulletin to dealers only. This Autochoke issue is not safety-related, and is covered under the factory warranty.
Safety-related issues are Product Recalls, and Honda will always send notification to registered owner by mail. Work required by a Product Recall will be done on any affected product, regardless of warranty status.
Where Can I Get a Copy of My Warranty?
Here's a link:
Honda Power Equipment Warranty
