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  #1  
Unread 09-11-2009, 09:37 PM
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Default Honda Lawnmower Tear Down

I thought this would be fun. I've worked on small engines in the past. I'm not talking just lawnmowers but TONS of small engines from RC cars, saws, mills, tracots to small and heavy equipment. Not to mention all the different automotive engines, motorcycle engines, rotary engines, etc etc

BUT I've never had a Honda lawnmower engine torn down! Why? Well they don't break! I've talked with many people over the past couple of weeks and the only person that has worked on the internals of a small Honda engine owns a mower and equipment shop. The Hondas just last forever. So what am I doing with one? Well a friend of mine has one and she decided to use it to shave some weeds down to the dirt in a field! The mower deck was at the lowest position and the air filter was super old and clogged to the max. So the result? The head heated up so much that one of the valve guides popped loose and the exhaust rocker broke.

I went over to try and start it and it would pop maybe but the noise was coming from the intake. So I looked at the filter and saw carbon and right then you know that the exhaust valve isn't opening. I expected to see the plastic cam gears inside the engine to be broken. I popped the bottom engine case loose and nope, everything looked just fine. The plastic lifter lobes looked to be in great shape and the lifters weren't frozen. What next? Well time to pop off the over head valve (OHV) cover. Every Honda mower has a nice big OHV cover on the top of the cylinder head that gives away that it's a Honda. They've made nice covers with those letter on it to let the people know that it's a quality engine with overhead valves.

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  #2  
Unread 09-11-2009, 09:41 PM
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Inspecting the inside. It's pretty amazing how precise everything is. I couldn't see any excessive wear and it's funny to see plastic cam gears inside. Mower engines are so basic inside. The Honda is just a really clean running engine and when you take it apart a 10mm is all you need basically. All the gaskets are high quality to they peel off nice and easy. On a Briggs & Stratton it's a whole different game. I won't go into how crummy those engines are built. The Honda is definitely a much nicer designed engine. But between the two I can see the need for a throw away B & S engine... no one wants to pay a dime more than they have to for a mower. But the Hondas are so nice and last so long I highly recommend them as the smart money buy. What a nice little engine. The only reason I'm having to work on this one is simply because of operator error... literally this mower was run into the ground until it stopped.





Yeap, everything looks fine inside. At least it's good to check and see how the engine looks inside before spending all sorts of money on it.

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Unread 09-11-2009, 09:42 PM
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So anyway I could jiggle the rockers really loosely so I knew then something was wrong. They should be pretty tight. Once you loosen the 10mm retaining nut and 14mm pivot nut from the rockers you can take them off to inspect them. At that point the pushrods also come out of the engine so I put those to the side. I actually thought that the valve rocker was the whole problem so I ordered a couple new ones to replace them both. In addition to those I ordered all new rubber seals, a blade assembly main bearing, and all the appropriate gaskets.



Order up some parts and had to wait a couple days for them to come in.



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Unread 09-11-2009, 09:50 PM
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Here is the culprit: you can see the exhaust valve lifter raised up out of the aluminum casting. The rocker is removed and looking inside the valve spring you should see a nice slim valve stem but you see a much thicker valve guide that has popped up. The top of the valve stem can be seen as it is being held up by the valve spring retainer cup. So you know that inside the valve spring that you see, there should be slim valve stem. This guide won't let the rocker arm push the valve down but the pushrod simply forced the rocker to break down the middle. I'll post a picture of the broken rocker later on sometime. We were lucky that the pushrod didn't bend as well.

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Unread 09-11-2009, 09:55 PM
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Here is how it looks all assembled and gapped. In this picture you can see the intake valve actually being pushed down by the rocker nearest the camera. What a clean engine. These Hondas are a pleasure to wrench on. It's just a little jigsaw puzzle that you can completely rebuild in a few minutes with hardly any tools.

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Unread 09-11-2009, 09:56 PM
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Another look inside the engine base cover.

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Unread 09-11-2009, 09:57 PM
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The gasket surfaces all clean and ready to reassemble. The cam gear is pushed in and ready to go another 10 years.

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Unread 09-11-2009, 09:57 PM
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Don't forget to line up the cam and crankshaft timing marks! They are hard to see but they ARE there for you. Once you have the lined up don't forget there is a very slim washer that goes down over the crankshaft and it comes to rest on the crank gear you see here. It mostly conceals the timing mark so don't forget to put it back on before you put the cases back together.



Here is that pesky washer just as I was taking it apart.

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  #9  
Unread 09-11-2009, 10:08 PM
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So that's it! Slap that thing back together and be careful reinstalling the control rods when you put the carburetor back on. I put the engine back on the Honda deck and it literally started up on the first pull. Great engine. Now I know what the Honda mower engines are all about. You get what you pay for. This whole engine rebuild was done with a regular screwdriver, a phillips driver, a 10mm 1/4 drive deep socket, a 12mm and 14mm 3/8 drive with a long extension, needle nose pliers, a spark plug socket, a gasket scraper and that's it.
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  #10  
Unread 08-05-2010, 07:30 PM
seandil seandil is offline
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Smile I am about to replace the rings and head on my Honda.

Hi,
Thank you for the pictures you posted. I found them doing a Google search. I have a hole around my spark plug hole that took out some of the threads and the engine will not start. I broke my recoil starter trying. I was going to take it apart, but unlike my other Honda its the black metal type that requires some kind of punch to do it, so I guess I'll have to buy a whole one rather than just replace the spring or what's broke.
I was wondering if I could tear down mine like you did yours and what the differences would be. My mower has been smoking allot on low RPMs or throttle SLOW position I use when I dump the bags. It a HR 215 K1 HXA model. I have done allot of work on it such as cleaning and re assembling the carburetor. I have allot of tools and feel I can do it. Mine is self propelled and another site suggested removing the driveshaft first, and go from there. I am thinking new rings, and a cylinder head with new valves is what I need to do. I can use my other parts from the head during re assemble. I read other forums and they suggested changing the rings would fix the problem. I did this to my Honda motorcycle and have a ring compressor and stone type cylinder hone, so I know I can do it. Doing it right is what I am concerned with. I never got that 'X' 60 degree pattern correct that you glaze into the cylinder while honing.
I am wondering if I can leave the parts on you did? It looked like you went through the bottom of the motor and did not remove the flywheel? Please let me know what steps you would do or some kind of order to do general things in.

Thanks
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Unread 08-09-2011, 10:13 PM
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Woops I didn't realize I had a question posted here! Sorry Seandil! Well better late than never I guess...

I would just recommend a light resurfacing of the cylinder with a "ball hone". You can Google this tool and then go to Youtube for instructions on how to use one. They are really easy. Then just tear down your engine like you see in my pictures and replace the piston rings. You simply remove the cap off of the piston rod and be careful to remember the order and parts you removed. Then buy a ring compressor from your local auto parts store to reinstall the piston with the new rings. It's pretty easy and you can find people showing how to use these tools on Youtube. Then just make sure to look at the valves and knock off and sand down any carbon that might have built up on the surface of them as well as the cylinder head. Simply put things back together and you shouldn't have any oil burning through the muffler like you did before. In the worst case scenario you might have to replace the valve guides but I wouldn't think so.

For valve guides
you would have to remove them by heating up the cylinder head really hot and pulling them with a special tool. To do this I would recommend finding a machine shop and paying them a max of $40 at the MOST to do this procedure. Make sure and have new valve guides in hand with your engine apart in a box. It should only take a few minutes for them to take the old guides out and put new ones in.
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Unread 08-09-2011, 10:21 PM
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I actually just adjusted some over head valves in a diesel generator I just acquired. This unit is powered by an OHV ETQ diesel engine and can be seen by clicking on the ETQ diesel generator link here. The valve adjustments and engine layout are VERY familiar and similar to the Honda engine. All engines with OHV use the simple design that you see in this Honda engine. Even though the generator is diesel it still uses a pushrod design and is arranged the same as the Honda. Very simple little engines. There is nothing that a "do-it-yourself" type of guy or gal can't fix with these. The only hard part that would require more experienced help is replacing a crank shaft, boring a cylinder for larger piston and rings, or replacing the piston rod or something. It's pretty rare that a repair of that nature would be required so if you find any of these engines in the dump or someones trash the odds are that they will run with a minimal amount of repair work. Just make sure you don't go digging out a beat up machine that is missing parts! If parts are worn out then maybe you can replace them. But if parts are missing then that starts to add up in price really quickly.
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  #13  
Unread 08-10-2011, 12:20 PM
seandil seandil is offline
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Thanks Smithers,
Actually, I have not begun that repair. I actually forgot about the post as well, but will heed your valued advice. I have one of those other type of cylinder hones and will have to use it.
It has three or four 'prongs' that have stones on them. I re-honed my motorcycle, and never got those 60 degree "X" pattern marks right. I could not pull out the hone from the cylinder fast enough with out damaging the hone. I am talikng about the up and down motion during the honing process.
Once it snapped out of the cylinder and threw the stones out (they were glued on by somebody). Next, they flew across the garage and broke. I got replacement ones. Do you have any advice for using this type of honer? I was advised by someone to take off as little as possible of the cylinder, and arrange the rings in a 8,12,4 o'clock pattern and to install them correctly. That is not upside down, and in the correct order. If done so I was told that the engine smoking problem would be solved?

Let me know and thank you sir.
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