OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk HONDA GXV140 self propelled.

Hello,
I bought this mower from the recycle centre.
(HONDA GXV140 21 inch cut 2 speed self propelled - GJAB-7422936 MAJ*)




It is turning over freely with no noise.

It had no compression. I used a gauge, zero compression.

The tank was full of water.

Ignition system is working, the plug had excessive oily black carbon deposits.

I haven't been inside one of these yet. I plan to pull it apart to find the reason for no compression.

I am on wireless internet and it is not always reliable for my responses.
Thanks

It probably has a bunch of problems Mark, with compression just the first of them. If you take off the rocker cover you can see if it has a stuck valve. Also of course, check the tappet clearances, observe the movements of both valves as you rotate the engine, and watch for the action of the decompressor: the exhaust valve should "bump" open slightly and momentarily in about the middle of the compression stroke. Look whether the head gasket is intact: I've never heard of one blowing on a GXV140 but if the previous tenant took the spanners to it, who knows what might have been affected.

Once you've done that simple stuff, if you haven't found it I think it will be time to take the head off to check for more serious problems like a broken piston or connecting rod.

Thanks Grumpy,
I have found the top valve is stuck.



I noticed the bump in the lower exhaust valve.
The clearance was an easy 0.01"

If you just bump the end of the stem of that stuck valve a few times with a piece of broom-handle exactly in line with the valve stem, tapped carefully with a mallet, it may free up. You'll find you can remove the pushrod and turn the rocker a bit to make this possible - don't hit the top of the rocker, even with a broom-handle. (You could tell I used to work on English cars in the long-ago, couldn't you? The British specialised in making lousy piston rings, so we tended to need ways to deal with carbon build-up.)

Valves don't stick without a reason, and that GXV140 having been a very favoured model among mowing contractors, the reason is likely to be a build-up of carbon on the stem, caused by oil-burning. If there are external indications of oil-burning you are going to have to replace the piston rings anyway, and it would be kinder to just take the head off in the first place so you can remove and clean the valves rather than unstick them.

The GXV140 went out of production in 2003, and I believe the last of the HRU195 & to a lesser extent HRU215 mowers that the contractors loved so well was sold new in 2007, so your machine probably has one or two hours on it by now. You can be lucky - mine had its base ruined before the engine wore out, so it's still pretty good. A nice engine. Yours being self-propelled will have a cast iron camshaft I think. The plastic camshaft in the push-propelled model was one of the few things I don't really like about that engine, but I haven't personally seen a worn out plastic camshaft in an engine that hadn't been pulled down previously.

Thanks for the info,
I had removed the head and only pushed on the valve with my fingers so far.
I am in no rush with this engine, I am just tinkering with it and it is a good learning aid for me.

Is it worth soaking the head first or spraying it with something before I start tapping the valve?

#Intake valve stuck open#

Its Ok, I gave it a spray with inox, let it sit for a while and gave it a slight tap with a rubber mallet and it is moving, I will be able to get it out.
I will clean all carbon from the head and valves.

Now that you have the head off, it is much better to just remove the keyhole valve retainer and take the valve out, so you can clean the stem properly. Of course you can only do this if you can push the retainer down far enough on the spring to get the retainer to push off sideways. You probably can: valves always stick in the fully-open position, as determined by the cam lift. There is always some extra movement available before the spring is fully compressed to its solid height.

If you can't get the retainer off, you will have to tap the valve head very lightly indeed, with a piece of wood, accurately in line with the stem axis, until it moves up just enough to enable you to get the retainer off.

In the picture you can see that the stem of the valve looks pretty clean, so you will most likely find that the first light tap on the valve head unsticks it and makes it close fully. Now that the cylinder head is off, of course you should remove and clean both valves, stuck or not, and lap them in.

The chamber looks oily, so it seems you will need to replace the rings. Check the ring gaps and bore size before you order them, of course. Unfortunately GXV140 rings aren't as widely available as GXV120 ones, and are likely to cost considerably more. I've bought good chromed GXV120 rings, with chromed steel rail oil rings, for $11 including postage - but the best I've seen on GXV140 ones is nearly three times that.

When you open the crankcase, please post a picture of the camshaft. You will be aware that the self-propelled drive is by a pair of helical skew gears, one on the camshaft and the other on a special self-propulsion output shaft. That means the self-propelled models have a different crankcase cover to suit, but the same self-propelled cover fits all of the crankcases. I've put a GXV120 one on a GXV140, but haven't yet put one on a GXV160 - but I think it's the same. The reason I'd like to see a picture is because the GXV140 normally has a plastic camshaft, driven by a plastic timing gear. I can't imagine anyone trying to use a plastic timing gear to drive a self-propulsion mechanism, so I'm expecting to see a cast iron camshaft, which the GXV120 and GXV160 have on all models. It would be nice to know if the self-propelled GXV140 actually uses the camshaft from the self-propelled GXV120 - we might be able to tell from the identification markings.

Water in the fuel tank, not a good thing.

Intake valve is the lower one in the image.

Looks like the water was in there a while. Water in the carburetor is of no great importance, but a valve stem rusting onto the guide means water inside the engine. Let's hope the crankshaft journals are OK. As a first guess, the water got in there after the mower was tossed out by a contractor due to oil smoke. Hence there was probably an oil film at least on the big end journal and the bottom journal. The top main bearing is a ball race on GXV Hondas, let's hope the water didn't get up that high. I think the odds are pretty good.

I suggest you remove the flywheel, open the crankcase, lift out the camshaft*, dismantle the big-end, pull out the crankshaft, and pull out the piston and rod. Remove the piston rings, measure the cylinder bore diameter, and then measure the ring gaps. Take out the tappets to check for rust. Check the camshaft for rust.

*GXV Hondas usually don't have a timing mark on the crankshaft timing gear. You can get by without one, but I always make one with an automatic center punch before I pull out the camshaft.

Flywheel didn't want to come easy.
Did some cleaning, I have had a quick look for rings online.



I will pull the case apart tomorrow.

So far today, have removed boss, both keys and clean rust off shafts. Removed bottom plate.

Yes Grumpy there is no mark on the timing gear, I will scratch a scribe mark on it.

Cam is metal.

Some people take pictures of flowers or landscapes, I take picture of engine parts, am I normal?
Images of internals taken straight after, haven't cleaned anything.


I have found some rings, I would like your opinion on them if that is Ok before I order them.

It looks very clean, which is promising. On the other hand the crankcase cover gasket broke, which is sad. The gaskets are expensive.

When you lift out the camshaft, I'd like to see a picture of any identification marks cast into it, so I can compare them with a spare GXV120 self-propelled camshaft. Meanwhile I have found that Partstree gives the same part number for the GXV120 and GXV140 self-propelled camshafts. This suggests that these camshafts have the same valve timing, strongly suggesting that non-self-propelled GXV120 and GXV140 camshafts will also be interchangeable, so anyone who is unhappy with his plastic camshaft on a non-self-propelled GXV140 can replace it with an ordinary GXV120 cast iron camshaft. Also a bit off-topic, the GXV120 in my weekly-mow machine, an early 4 height-lever Honda with an HRU194 blade system, is currently fitted with a GXV140 crankshaft (generously given to me by vcomm - thanks for that). For background, the GXV120 and GXV140 have the same stroke but different bores, so they share common crankshafts and connecting rods. The crankcase cover is also the same.

Your GXV140 flywheel is made of aluminium, unlike both GXV120 and GXV160 flywheels, which are cast iron with plastic cooling fans. I've never noticed that before. The extreme lightness of the GXV140 engine begins to be understandable. I will take this opportunity to warn people that the ignition module mounting points for the GXV140 and GXV160 engines are different from those on the GXV120 engine, and as a result you cannot fit a GXV120 ignition module to a GXV140 or 160, and vice versa. Also, while the GXV120 and GXV140 cylinder heads are very similar, note that they are for different bore sizes. The GXV160 cylinder head, despite having the same bore as the GXV140, is different again because it has a much larger intake port.

Getting back to the business at hand, I don't see any signs of water in that crankcase, yet your inlet valve stem was rusted onto the valve guide. Unless you find some water drops in the crankcase somewhere, I'm mystified.

I'm happy to comment on a piston ring set you consider buying, but I recommend that you measure the bore, and the ring gaps, before you place an order. We have not yet proven either that the block is serviceable, or that the rings are worn out.

Some images.

Plan to do some measuring. (I have a micrometer and internal calipers)

The bore has rusty marks from the rings (closest measurement I can get is 64mm), but otherwise seems OK, I could give it a hone, I have the type with the balls on the ends of wires.

Rings where rusted into their grooves and hard to get out.
Crank pin measured at 26mm.
Ring gap in bore 0.4mm.

Whoops, that crankpin and the connecting rod bore both look nasty - seems like it's run dry at some point in its history. I've thrown away better crankshafts. Here is one I stopped using because the crankpin is worn nearly but not quite to the service limit (nominal diameter is 1.024", minimum allowed is 1.020", this one is 1.0206", and the engine had an audible knock at idle only):


Note also in that picture, my spare camshaft (from a self-propelled GXV120) has no ID marks at all.

You have steel rail oil rings, which is good. In an iron bore, they generally last considerably longer than cast iron ones.

To measure your bore diameter accurately, you can't just use a sliding caliper, because that only measures the diameter of the ridge above where the top piston ring comes to at the top of the stroke, so it doesn't show any wear at all. To get an accurate bore diameter you need to use this:

It comes as part of this set:


You probably don't want to buy that, it's expensive, so you can get an approximate measurement by using this inside caliper and transferring the diameter to your sliding caliper:


If you can't borrow one of those, you could just measure the ring gaps and we can try to guess what is going on from that.

Essentially, GXVs that have been serviced properly and terminated when they started to blow smoke, have 0.002-0.003" of bore wear. If they have fallen into the hands of people who want to run them into the ground despite the smoke, they may have very much more wear because it becomes impractical to keep oil in them, and they end up swarf-lubricated (well, hopefully the swarf layer in the sump is kept slightly wet with oil, to keep them from seizing up). The crankshaft in my picture came out of such an engine - hence the crankpin wear. It also had 0.007" of bore wear. I don't think your engine has had that kind of experience, or the piston would be scuffed - I think yours was just run dry once, then cleaned out and filled with oil.

0.4 mm ring gap is only 0.016". That is the top limit for a brand new engine. The service limit for a used engine is 1.0 mm (0.039"). If the other rings have similar gaps, they do not require replacement, and the bore can't be worn very much or the ring gaps would be greater than they are. In other words, you do not appear to need new rings - but you should clean out the ring grooves in the piston carefully without removing metal, and clean the rings so they have not grit or rust on them. You should not formally hone the bore - I would just clean it with some 400 grit paper, swashed around in the bore with my finger tips.

I can make a new guess as to what happened to that engine: it did not run until it started to smoke, it ran until somebody accidentally ran it without oil and seized it up, whereupon they panicked and scrapped it.

I suggest you clean everything up, linish the crankpin with 400 grit paper until it is smooth but without removing any measurable amount of metal, do the same with the rod bearing, put it back together with lapped valves, and start work on cleaning the carburetor.

I have measured the pin with the micrometer, I get 25.98mm which converts to 1.0228 inchs.

I can feel ridges in the pin with my fingernail.

Could I get away with using this crank and a new connecting rod.

I will look at bore size next.
Thanks for all your comments so far.

The pin needs to be polished, Mark - you can't use it with substantial grooves around it. If it gets anywhere near the minimum diameter (1.020") it is scrap. Remember that I had a knock at idle from one that was above the minimum diameter (it was 1.0206"). Note that at present, measured across the high points of the grooves, it is still the correct nominal size for a new crankshaft, so the whole issue revolves around how deep those grooves are.

You always classify the crankpin by the smallest diameter you can find. That always turns out to be measured vertically when the crankpin is 20-30 degrees past TDC, which is the crank and rod's position when there is maximum gas pressure in the combustion chamber.

The maximum allowable diameter of the rod's big-end bore after you polish it up is 1.0264". However the rods are not expensive, so recovering it is not a good idea. I'd clean up the crankpin and see what its diameter looks like. If it is say, at least 1.021" at its smallest place, I'd put a new rod on it and put it back to work. At least that way you get a rod bearing that is less than 1.0248" diameter. In my experience big ends get noisy when the clearance gets to 0.003" or more, so if you meet those dimensions, at worst you would end up with an engine that has an audible knock at idle only.

Thanks you for your appraisal, I don't like asking questions like that, I guess a worn engine is exactly that.

I've taken a series of bore measurements: 64mm to a maximum of 64.3mm.
So largest size there = 2.531". I cant see a maximum bore diameter in my spec's.

I will try to clean the crank pin up with fine wet and dry paper with lubrication, with the aim of keeping it smooth and round.

I will try to make the best of things with what I have.
I would like it to be perfect, but it is looking like being a compromise.
Try to come up with a repair option before I order some parts.

Images of crankpin each side after first clean up.
Size is 25.975mm - 1.0226"


I think I'll polish it a bit more, I can just pick up the grooves with my fingernail.