OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Honda Engines Honda GCV160 mower

This is the image of the carb. As I mentioned in my first post, I did not recall a spring loaded set screw when re-assembling the carb. The images included in the response included one drawing with the set screw circled. I just don't see any similarity between the two.

I am hoping the posted image will assist in troubleshooting. It may even be something unrelated to an idle screw.

Most perplexing is the fact that before the rebuild(which was unnecessary) the mower ran just fine at the proper factory settings(whatever they are). In other words I was not alarmed by the operating characteristics at the time, unlike presently. If the image is not clear enough, I can reposition and resubmit.

Hope this helps.

Centexn

Hi centxn, it looks to me as if your engine may have a design change not covered in the workshop manuals I have. Here is your picture of your carburetor, with the normal position of the idle speed adjustment screw circled in yellow:


As you can see, your carburetor just has the hole for the idle speed screw, but no screw is fitted. Can you tell us whether there is a thread in that hole please? Also, if you look at roebuck's picture of his GCV160 carburetor, you will see that it has a tang on the throttle butterfly bell crank for the idle speed screw to hold the throttle partly open (circled in red):


I cannot see in your picture, whether your carburetor has this tang.

If the throttle speed adjustment screw-hole has never been tapped, and your carburetor does not have the tang for the idle speed screw to press against, your engine may have a feature that is not found on any of the Honda engines I have seen to date. The feature is one that Briggs and Stratton call "governed idle", and it eliminates the idle speed adjustment screw, replacing it with a spring mechanism attached to the engine's governor, to control idle speed. On the other hand if your carburetor has a tapped idle speed screw hole, and a tang on the throttle butterfly bell crank for the idle speed screw to press against, it is much more likely that the idle speed adjustment screw is just missing from your carburetor. Hence we need to know more about your carburetor before we can proceed.

Note that the published Honda workshop manuals show an early version of the GCV160 carburetor, which I included in a previous post. roebuck's picture is of a later carburetor, not covered by the manuals, which is similar to yours but has provisions for an idle speed adjustment screw.

If you can show us enough detail, we can try to figure out whether you have missing parts, or alternatively, you have a governed idle system which we will then need to investigate and understand. It is fairly likely, if you have governed idle, that the choke mechanism is slightly out of adjustment and is simply causing the idle speed to be increased, but we will be able to resolve this if we see some additional pictures of the engine with the carburetor installed.

Here are a couple of pics of the spring powered linkages with the carb in line. The air filter has been removed as you can see so everything shown is as it was just after the rebuild.

[quote][/quote]If the throttle speed adjustment screw-hole has never been tapped, and your carburetor does not have the tang for the idle speed screw to press against, your engine may have a feature that is not found on any of the Honda engines I have seen to date.

This is the case in point. Those conditions present themselves.


Clearer pic of carb:




I hope these images provide enough additional info to clarify your thoughts.

Centexn

Can we see a picture or two of the fully-rigged throttle and choke linkages attached to the carbureter, viewed as nearly as possible from directly above? I need to see the link(s) that set the throttle position, at both idle setting and maximum speed setting, so we can see how the throttle position is set. Briggs uses a second governor spring to operate at idle only, and the idle speed is adjusted by bending the bracket that holds one end of the idle spring. What I am concerned about, is that the throttle linkage may not be correctly assembled. Since at this point I don't know what "correctly assembled" would look like, I need more pictures to try to work out what controls the throttle position.

As you will notice on the second of the two side views showing the linkage, there are only two springs. The top one connects directly to the butterfly valve mechanism on the top of the carb. There are two connection holes in that mechanism. The top spring is connected to the outer most. The lower spring connects to the aluminum housing in the foreground.

Unfortunately, at the time I disassembled the carb, I did not take any pics)(big mistake) primarily since I believed there would be docs and pics online which could give me the linkage set up. I even went to a retail outlet to find similar models to get an idea. Of those, the linkages were either covered up or updated model which did not match mine. PDF versions of owners manuals did not cover this detail. So, thats why I showed up here, lol.

Centexn

centxn, to clarify what I am talking about in the previous post, look at the area boxed in yellow in this copy of your picture above:


Compare it with this diagram from the service manual, for the traditional GCV160 governor system:


As you can see, the traditional system, with screw-adjustable idle, just has a wire link from the governor arm to the throttle butterfly on the carburetor, with an anti-oscillation spring around the outside of that wire link. That is the whole system.

Your engine has a complicated-looking stack of apparatus on top of the throttle butterfly, with no direct wire link from the governor arm to the throttle. There is just the usual anti-oscillation spring from the governor arm.

Note the slot circled in yellow, in the throttle butterfly bell crank:


It looks as if that slot should engage with a device on the bottom of the complicated stack, because if it does not, there is no real control of the throttle position - the anti-oscillation spring cannot control the throttle, though it can hold it partly open when speed is set for minimum, and open it more when speed is set higher. In your other picture I see a strange device on the bottom of the complicated stack, which might or might not be involved in the throttle control process:


Can you show us some detail about the bottom of the complicated stack, in particular any part which might be capable of engaging with the slot in the throttle butterfly?

It looks to me as if there is something in that governed idle mechanism that causes a problem when it has been dismantled and reassembled by someone who does not know the secret, whatever that turns out to be. Check this thread:
http://forums2.gardenweb.com/forums/load/lmower/msg06151832696.html

Because the anti-oscillation spring holds the throttle partly open when the speed control is set for minimum, just lifting the carburetor up into position under the complicated stack, would probably not result in the right part of it engaging in the slot in the throttle butterfly. It would be necessary to push the butterfly toward minimum throttle, while lifting the carburetor.

Attempted to label components. The diagram above showing what you have labeled the "traditional system" requires a comment or two.

First, there are two butterfly valves. One for the throttle which is metal and inboard of the second for the choke which is made of black plastic.

The diagram indicates two linkages from the governor arm. One is a spring, the second is a sturdy length of wire both ending with a connection to the throttle butterfly valve. Now take a look at your return pic to me, the one with the yellow square.

Notice the heavier wire is not connected directly to the throttle butterfly valve. Only the spring is connected to the TBV. This set up is contrary to the "traditional system" diagram. Part of the reason is that the manual choke activator is actually part of another mechanism controlled by a cable running up the the dead man's bail on the handle. To start a cold motor, the mechanical choke is set "on" by pulling it rearward to the stop. This physically positions the clutch butterfly valve open by mechanical linkage(see red circle). Closing the bail allows the motor to start when the lanyard is pulled. As the motor warms, the choke mechanism automatically closes as long as the bail in held closed. Once the motor is warm and the choke has closed, the spring loaded governor arm is now in play to allow for constant rpm under varying load.

I can find no adjustment for idle rpm which leads me to the governor set up, which has been suggested as the way to adjust the engine rpm. On your dia "traditional system" there shows a lock nut holding the governor arm in place which when loosened allows for the governor adjustment shaft to be rotated to control rpm. Anti-clockwise is supposed to reduce rpm, clockwise is supposed to increase rpm. I have tried this, but could not budge the governor adjustment shaft anti-clockwise.


Therein lies my issue. Perhaps I didn't use enough oooomph in turning that shaft. I don't know. Anyway that's my two cent contribution to this qusst.

Centexn

centxn, thanks for the additional details, which clear up most of my questions - the choke mechanism, which Honda calls an automatic choke, is now fairly clear.

So far as the actuation of the throttle butterfly is concerned, I am doubtful that this can be done effectively through the small spring (very similar to the anti-oscillation spring on the older design) which is currently the only connection to the butterfly. However the first step toward clearing this up would be to adjust the governor, so that it is eliminated as a possible source of the problem. If the problem still remains after adjusting the governor, we can discuss it further.

Here is the section from the free-on-line manual, describing how to adjust the governor linkage:


Please read the next part while referring to this picture:


It is fairly uncomplicated. Essentially you loosen the clamp bolt (yellow circle) at the bottom of the governor arm, pull the top of the arm (green circle) all the way to the right, and rotate the governor arm shaft (red circle) (on which the bottom of the arm is pivoted) clockwise as far as it will go, by using a small wrench on the flat shown in the red circle. Then, holding both arm and shaft in this position, you re-tighten the clamp bolt. The purpose is to remove any slack so that the paddle on the far end of the governor arm shaft, inside the crankcase, is in contact with the plunger on the centrifugal governor mechanism.

The difficulty you had in making this adjustment was probably caused by minor corrosion of the joint between the governor arm shaft and the governor arm. After backing off the clamp nut a couple of turns, just hold the arm stationary, and rotate the shaft with the small wrench, to free up the joint.

I now think you do not have governed idle, all that has happened is that Honda has applied the dreaded "value analysis" engineering approach and has found a cheaper way to make the idle speed adjustable. Look at the part of this picture that is circled in yellow:


Instead of having a screw to adjust the idle speed, you adjust it by bending the tang that is closer to the fixed stop on the carburetor.

When you have adjusted the governor, let's see whether it is able to work despite operating through a weak spring instead of a strong link. With the engine running and the speed control set to idle, the throttle butterfly needs to rotate anticlockwise when viewed from above, until the tang contacts the fixed stop. If it doesn't, we will need to look closely at the governor linkage setup.

Post Edit: There have been no posts to this thread for some time, so it has probably been abandoned. Frankly, I've suspected for some time that this engine should have the normal wire governor link running through the center of the anti-oscillation spring, and that link is simply missing, rather than not being required on this model of engine. I was hoping this theory would either be confirmed or disproved as the thread went along, but it has not happened.