OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Honda Engines Honda GXV 120 smoking/overhaul help please

First, if there are three rings, it is usual to fit the ring gaps at 120 degree angles to each other. I was taught long ago to fit each ring at 180 degrees to the one above it - in those days there were often 4 rings, sometimes more, so even spacing wasn't going to cut it. Usually, I tend to just do what the workshop manual says, which in this case is 120 degrees.

The folded mesh screen in the PCV compartment stands on edge in the deep vertical slot in the bottom of the compartment. You want it to get in the way of pressure waves passing into the breather tube, because the role of the screen is to filter out tiny droplets of liquid oil: you want the droplets to trickle down through the mesh, then run down the slope at the bottom of the slot, to the drain-hole at the opposite end of that slot from the port leading to the breather tube. There is a baffle in the compartment, so you can leave a space between the end of the mesh and the breather port. If you don't do that, the section of mesh positioned up against the port could get crudded up and obstruct the port. See this picture:


Honda's design of that compartment, as of most things, is rather well thought-out. And the picture is of a scrap GXV120 block - there isn't much point in cleaning scrap, in my opinion anyway.

Remember to push a 1/16" drill bit downward through that drain-hole, then pull it back out:



The picture is taken from inside the crankcase, of course. The red circle is around the drain hole.

The tiny drain-hole sometimes becomes obstructed by a build-up of crud over the years, and that is a problem because it results in the compartment gradually filling with oil, which then goes through the breather tube into the engine intake. So, just hold the drill bit in your fingers, push it deeply through the drain hole, then pull it back out. This is done from the PCV compartment - you don't need to do it from inside the crankcase.

The inside of this engine looked nearly new. The drain hole in the breather compartment was completely open. I understand the function of the screen now that you have explained it. The way it is shown in the picture the opening to the breather tube is unobstructed as you said and the screen also is not over the drain hole. I have unfolded the screen and re-folded it trying to make it wider so it would fit more snugly in the vertical slot. But the screen still does not fit snugly. I wonder if the screen could move on its own over time and end up blocking the opening to the breather tube?

I just inspected one, and it is a tight, jam-in fit in the deep slot. I couldn't persuade it to move along the slot with light pressure from a piece of rod. I'm used to them being fairly tight in there. You might try to slide yours along and see how far it will move toward the breather port. The compartment slot curves around in that direction, and I doubt the screen will be able to curve enough to move along, but if it can, I think you'll need to replace the screen.

Thanks for the tip. I unfolded the screen again and this time I placed a 1/4" diameter rod in each crease and folded the screen around the rod. After I did this the screen fit snugly so I don't think it will move. It has the most resistance when moving toward the opening to the breather tube. It moves a bit easier toward the drain hole but it seems to be snug enough so it won't move. I will check it again tomorrow to be sure it does not relax enough so it moves easily again.

That sounds fine, Terrys. As I said, I'm doubtful that it can slide very far toward the breather port anyway, because the channel is curved near that end, but they are usually fairly reluctant to move at all, which seems the best way to me.

I am putting the case halves together. There is a threaded hole in the case about 3/4" from the round plastic tip of the governor assembly. I don't find anything that can go there and nothing shows in the diagram that I have. You can see the hole in the 10th picture in the following post.
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=47175
The hole is just below the tip of the governor assembly in the picture and has some oil in the hole.
It appears that this hole is not used but I don't want to put it together and leave something out.

Next problem>>>> Cleaning the carburetor I took the plastic part out that is below the throttle stop screw. I think it may be called the pilot tube. It has a small o-ring at the bottom. I think it may be called the pilot tube. In the video it shows cleaning out the small hole from the end the o-ring is on. It looks to me like there is a tiny hole in there but I have tried to push a tiny wire .0185" through but it will not go. The carburetor was pretty clean. No sign of varnish etc. I wonder if my carburetor is not supposed to have a hole there??

That is the pilot jet in Honda-speak, or the idle jet to most of us. The hole in the center of the lower end, near the O ring on the outside, is the actual jet. It is only 0.014" diameter, so it requires an unusually small probe. Honda says you should use an ultra-tiny gas torch cleaning probe, but standard sets of torch cleaners do not include a small enough one, and I have never been able to find one that small, so far anyway. I think most of us just buy a set of jet drill bits like these:
http://www.ebay.com.au/itm/Metric-I...DefaultDomain_15&hash=item5b11ddcfcd

Of course that makes more sense for those of us who face carburetor cleaning chores more or less regularly.

Remember that the Honda idle jet is just a plastic moulding, and it is quite difficult to deal with cleaning it without making the calibrated hole larger. The non-genuine ones (for Chinese Honda-copy engines, commonly called "chondas" here) have a brass bush lining the calibrated hole, and I personally prefer that.

Because you have no reason to suspect a problem with your idle mixture, I suggest you just remove the O ring, blow through the jet, squirt some carburetor cleaner through it, wash it in gasoline to remove the carburetor cleaner, which is quite unfriendly to plastics, put the O ring back on, and reinstall it. Do not allow carb cleaner to touch the O ring.

Thanks for the reply. Did you see my other post about the threaded hole in the case?

Sorry Terrys, I missed that post. Let's compare three GXV120 crankcase covers. Here is chris125's from the other thread you cited:


As you said, it has a hole near the centrifugal governor mechanism. I can't tell whether it is tapped or just a cored recess in the casting.

Here is the crankcase cover for a self-propelled model which I happen to have.



As you can see, it has the same hole, but it is not tapped and may be for a feature only used on some models, or a left over feature that Honda's engineers thought was a good idea initially but no longer use.

Here is the crankcase cover for a non-self-propelled model which I also happen to have.


As you can see, the cored hole is not present. Perhaps by then Honda had deleted the feature from the tooling, or this was made before they added the feature to the tooling.
In any case, I don't recall seeing a GXV120 in which that hole was actually used to attach anything.

Thank you very much. I really appreciate your fast replies and excellent knowledge.