OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Honda GXV140 engines - HRU195

Hello, I have cleaned down these two Honda mowers and have been assessing them as I go.
I plan to make the best one I can out of the two.





Everything has come apart ok so far, except I have snapped an exhaust bolt while I was carefully working it back and forth.

One of the blade plate nuts just would not budge and I rounded it off.
I ended up grinding the sides of the bolt head down to make it a 13mm head, then eventually got it off.

So far it looks as if you should be able to make up 2 decent mowers Mark, not just one.

I was thinking the same thing, you should be able to get both of them running unless one of them has a major fault. One of them will obviously be complete while the other may have some cosmetic bits missing.

Thanks, it is stating to look as if I can get two engines working.
The newer mower pictured on the right, was found upside down on the scrap metal pile at the local tip. My wife recognised it as a Honda and a fella helped her load it into the ute.

Have been doing some cleaning and noticing some differences between the two.


Older engine is marked made in USA.


Cleaned out breathers, washed screen filter in fuel. Also ensured hole at the bottom was clear.


The jet drills make cleaning the carburettors a lot easier, I used to poke around the galleries with different sized bread tie wires.

All GXV140 engines were made in the US. At a guess, they initially had the Made in USA insert and it was dropped along the way - I have no information on that. All GXV140s had the serial number prefix GJAB, and no other Honda engine had it (that prefix is the most authoritative way I know to identify Honda engine models, by the way). All serial numbers fell into the range 6000001 to 7999999. The minor differences along the way are denoted by the "Engine Type", which for both of yours is MAC*. There are no references in the records I have to the trailing star, but every GXV140 in Australia that I've seen or heard of has the star - it may be an export identifier, but that is simply a guess. The Engine Types for GXV140 range from A1 to N2Y. All of the GXV140s in Australia that I've heard of so far, have Engine Types beginning with MA and ending with the star, but the intermediate letter so far runs from C to J. In case it helps at some point, the Paper Parts Catalogue Part Number for MAC engines is 10ZG901AP - this might be relevant at some time for buying parts, I don't know.

With well-used vertical Hondas, always inspect the brown fibre and resin PCV valve disk for wear. Every time it opens (every downward stroke of the piston) it hits the depressed part of the PCV compartment cover - circled in red:




This very slowly wears the disk away. You can see the wear depression in the one you photographed - the wear looks rather slight as far as I can see in your picture. Here is the worst one I have had so far:



I haven't been desperate enough yet to re-use that one: it is worn most of the way through.

I haven't yet seen an early enough engine to have that boss on the cylinder head that is on your older engine but not your newer one. Here is a closer view of that part of my spare MAH* cylinder head:



That is quite a substantial design change - my guess is that it was done for a good reason.

You will notice that while both of your engines have bosses for the mountings for both N and A type ignition modules (see other thread for explanation) in the older engine there does not seem to be a cored hole in the N type boss (GXV140s were only fitted with A type ignition modules). In your later engine the third boss has a cored hole, but it was not tapped. My MAH* cylinder head also has the cored-but-not-tapped third boss.

Now that I've gotten so far into the esoteric detail, I'm morally obliged to move this thread to Tech Talk.

Grumpy, have you ever flipped the breather valve over? I have put both of them back they way they came out.
I am well pleased with the condition of both bores, the amount of carbon cleaned away from the head and valves wasn't excessive on both.


Older engine.

Newer engine.

Next will be cleaning the heads up and lapping the valves.

Mark, I haven't flipped a worn Honda PCV valve disk, because I think that would make the situation worse. As the disk wears, a larger area in the center comes into contact with the stop, which is the inside of the pressed steel top cover of the PCV compartment. By flipping it over, you reduce the contact area to the small flat in the center of the stop, which would substantially increase the wear rate. (On the worn one in the picture I posted, that area had at least doubled during the wear that had occurred. Turning it over reduces it to what it was when the engine was new.) You also put all of the load onto the part of the disk that has worn thinnest.

My standard practice if I take the head off, is to measure the bore. So far with small Hondas I've found consistently that when the engine starts to smoke mildly due to ring wear, the bore will be worn 0.002" larger than standard. On those engines, so far I've been able to just replace the rings (with good quality sets - chromed top ring, chromed steel rail oil rings), look quickly over the other internal parts, check that the valves are sealing, and put it back together. I haven't yet needed to remove a crankshaft, let alone replace oil seals, and I may not have to remove the flywheel. (I was fooled on one occasion though: the previous tenant had stripped the internal thread in the output shaft, and I didn't find out until I'd put the mower back together. I had to go back in and replace the crankshaft.) However, I've had a couple of engines that had been abused - a second owner continued to use them without repair after they started to smoke slightly. Those ones, so far, have been run a long time with dirty oil and have worn bores, worn connecting rod bearings, and a multitude of other wear problems. All I can save from those is external items plus fasteners. Don't knock the idea of keeping spares of that kind - sometimes you can get a "bucket of bits" engine, which the seller always swears is complete, but never is, for $5 and make it back into a good one.

Ok, I will not flip any of these valves, what you said makes perfect sense.

I have taken some shots of the heads & valves, they have not been lapped yet.

old engine.


new engine.

I will measure bores to check for wear.

There is a mark on the inlet valve seat of the old engine. If it isn't a bit of dirt, it's a crack. That could be a problem, since it will propagate to the area that contacts the valve-head, and cause a leak.

The part of the seat that contacts the valve head should be 0.8 mm wide for a new engine, with a maximum of 2.0 mm as the service limit for used engines. I don't like to see them much more than 1.2 mm: it becomes difficult to maintain even seating all the way around. Note that by the time the seat gets to be 2 mm wide, there is quite deep wear to the valve head, and the valve has to be replaced. Remember, the inlet valve seat insert is not hard, but the exhaust one is. Re-cutting the exhaust seat calls for a diamond cutter. Don't make my mistake and try to re-cut one with a standard cutter, or you'll have to resharpen the cutter tooth by tooth, as I did.

This is how the valves and seats ended up.


older engine


newer engine

I think the inlet and exhaust seating-widths would have been the same when those engines were new, and the (soft) inlet seats have worn much more than the exhaust seats.

Don't forget to check for slack between the valve stems and guides, and make sure the spark plug threads are in good condition.

Hello, checked for play in valves guides and plug threads are good.

Measured both bores as best I could with my internal callipers and transferred that to my verniers to measure somewhere in-between 64mm and 64.1mm. Service limit is 64.165mm.

Both bores look good and I doesn't seem to be much wear.
Here are some images of where they are at (older engine is on the left).


Found gravel in the sump of the older engine, 15 odd pieces up to 5mm long, cant be good. I found a few scars in the teeth of the cam shaft and oil flicker. Other than that haven't seen any other damage as yet.


Older


Newer.

Had trouble getting the base plates off and the cam shafts dropped out before I could scribe a timing mark on the crankshaft gear. So will have to find another way of timing them when I reassemble.
Cheers

The older piston is fairly well scored, Mark. Personally, if I had a spare piston I'd use it, because the rest of the engine looks decent.

My system for getting by without a timing mark on the crankshaft timing gear, is I put the crankshaft on TDC, then insert the camshaft so that its timing mark is at the closest point of approach to the crankshaft. Of course you have to allow for the spiral gears, so you enter the teeth nearly 1 tooth anti-clockwise from where you want it to end up. I prefer to use a pair of timing marks, and that is why I make one before taking the camshaft out, but it isn't actually necessary, and isn't recommended by Honda. In case you care, the reason there is no mark on the steel crankshaft gear, is that it isn't keyed to the crankshaft, it is just pressed on. Honda recommends pulling it off and replacing it if if gets worn or damaged, so they couldn't have put a timing mark on it in the factory in case the owner later removed the gear and replaced it, in no particular position.

I measured the piston skirts at 64.01mm
Service Limit is 63.815mm


I am just working out what parts I need. Measured the ring end gaps.





Older (second ring marked with an "O") top 0.031" sec 0.05" easy


Newer (no markings on rings) top 0.029" sec 0.048"

Noticed oil ring variation.

So it is looking like I have 2 worn pistons and worn out ring sets, with both cast iron bores holding up well.

That is pretty standard for Hondas and chondas Mark, but it takes a lot of time and work to bring them to that stage of wear. The nominal piston skirt diameter when it leaves the factory is 63.985 mm, so yours have no measurable wear, it's just that one of them is scratched. I'd replace the rings, certainly re-use the clean piston, and look at linishing or buffing the scratched one to smooth it out a bit - mostly, remove the raised-up edges of the scratches.

g'day, I have buffed the scratches on both pistons, they look better.

I set the timing as you said Grumpy. I also as a double check, put the fly wheel on to notice both timing marks, the one in the starter cup faces the long magneto bolt and the arrow on the flywheel aligned with the rear post.




I have started putting the newer engine back together and am awaiting parts for the older one.

I'll look forward to the road tests, Mark, but in my experience to date Hondas are neither difficult to work on nor sensitive to detail. It irritates me that Suzuki, for example, doesn't follow the same design principles as Honda. It needn't be difficult to get good results.

Some years ago I had a long talk with the American engineer in charge of engine design at a very large American car manufacturer. His engines leaked oil, and always had. Top management started telling him this had to stop, and he challenged them to show him a better engine. They told him to look at a Honda car. He went to a dealer who sold Hondas as well as his company's products, and asked the boss of the place to show him a Honda that didn't leak oil, if they had one. The dealer pointed out across his yardful of traded-in Hondas, and said, "Any of those". The engineer didn't believe him of course, so he picked one at random, and the dealer had it brought into the workshop and put up on a hoist. The engineer inspected it thoroughly, in growing disbelief. He could not find any place where the built-up dust on the engine was not completely dry. It was a long time after that before he got his own engines to stop leaking oil, and he wanted to give up a couple of times along the way, but he got there in the end, by blindly copying the way Honda did it.

I have got the newer mower back together. Put it on a nicer base.


On first start up it ran flat out and I had to shut it down straight away.
Eventually worked out the governor arm and its shaft were not set right.
Also had to reshape the connecting rod as it was all bent.
There was no anti surge spring, so the older engine donated its.
I ran it with out the surge spring to see what it would do, the result was when changing speeds it would take a while to settle smoothly at that rpm. (it needs that spring)

Also had trouble getting it to idle, found the governor arm was hitting the breather pipe. So the butterfly in the carb would never close off. (I cable tied the pipe out of the way.




The control rod and governor set up was a mess, when I get a new rod and spring I'm sure it will run nice, ATM it is surging a bit when mowing and takes a while to settle at a new speed.

Idle screw was broken off and locked in , had a bit of a go at getting it out, I have left it for now.

Thanks for trying it without the anti-oscillation spring Mark, I've never done that and consequently didn't know how much effect it would have - I'd expect it to do what it did, but I did not know how severely.

The set-up process for positioning the governor arm on its shaft is fairly standard for various types of engine, and needs to be done routinely when you are checking over an engine. Bad things can happen when you let one run uncontrolled, especially if it is someone else's engine and you don't want to be embarrassed by the results. I don't think you need a new rod and spring - just pull the governor arm fully to the right, hold it there, and adjust the central bend in the rod until the throttle is firmly wide open. The issue with the governor arm needing to be bent just slightly away from the crankcase so it doesn't rub, and arranging the breather hose so it doesn't touch the control rod, is necessary if there has been some ham-fisted handling of the engine before you get it, but not otherwise. However you always check of course.

With regard to the broken idle mixture screw, if you can unscrew it with vicegrips or whatever, it is not expensive to replace. I suggest you look on ebay, or send a PM to roebuck.

Hello All, roebuck has sent me rings and carb kit, so I am back onto this.
In the mean time I have been cleaning, derusting and painting parts.
I have made the best base I can out of the two I have for the older engine.
The remaining one I will clean up as a spare.

older engine parts.


Older engine base.


Spare base, major flaws: panel beat and weld bottom of handle, repair crack in base, holes in wheels plasic welded from old Victa wheel.
I will paint it with Kill rust "pewter", I use a brush.