An MTD Yard Machines 21" Rear Bag/Mulch Lawnmower

[Last updated: Sunday, October 20, 2019.]

It may well be a basket case that's destined to be scrap metal.

Model No. is 11A-413C500. Serial No. is 1L075I10657 000001. I managed to download an operator's manual from MTD's website. The manual is subtitled, "21" Rotary Mower -- Model Series 410"; I guess the '413' part of '11A-413C500' makes it one of 'Model Series 410'.

Engine is a Tecumseh 5.0 HP, 195cc. Here's a shot of the engine's ID label.

Here's a list of all the troubles that I can readily see.

• No compression to speak of.
• The dipstick shows nothing. The sump could be completely empty.
• The enable/kill bail is inoperative. The cable is probably seized. There's a ty-wrap holding off the engine brake at the engine bracket.
• It's missing the handlebar-mounted perch for the starter cord handle to reside on.
• The middle handlebar bolts are seized loose.
• There's a fair bit of deck rust bubbling up under the paint.

All-in-all, it's a sorry old, badly worn and neglected machine. If nothing else, it may be interesting to see how well a no-compression engine runs, if I can even get it to run.

Anyway, the first order of business is to see if I have spark. If not, it won't be worth pursuing the project; there's no point in investing in a coil for a worn out engine.

Spark Plug

It looks pretty rough and long-neglected from the outside. Let's see how its innards look. The hex on it is 13/16" A/F (across flats).

It's a Champion RJ19LM, a resistive-type plug, and it actually doesn't look too bad. Gap was a little over 0.030"; I snugged it down to exactly 0.030" and tried it with my spark plug test rig. I have spark! So, I can carry on with this project, for whatever it proves to be worth.

- - -

Spark Plug Update -- WEDNESDAY, MAY 15, 2019

Once I got the engine running, there was pronounced roughness and misfiring. I tried a different spark plug with the same reach, and the engine seemed to run better, so I bought a new RJ19LM.

To be certain, I put the original spark plug back in and tried it. Sure enough, the roughness and misfiring were back. I installed the new spark plug, and there was a definite improvement.

So, I have to change my thinking on spark plug replacement. In the past, I've been pretty lackadaisical and stingy about replacing spark plugs. I've always had the attitude that if the thing sparks outside the engine on a spark test, it should be ok to use. But it appears that there's more to spark plugs than meets the eye. While spark plug replacement is not a cure-all, it appears that it's definitely a contributor to engine performance optimization. I guess I'll be replacing a lot more spark plugs in future.

- - -

Compression Test

I did a compression test, and the engine registered about 50 psi. That's not great, but it's better than I expected from the feel of the thing. There's hope for the old machine yet.

- - -

Enable/Kill Bail Cable

The cable is MTD P/N 746-1137 according to both the operator's manual's parts list, and to the cable itself. MTD marks cable part numbers right on their cables' jackets, so you really can't go wrong. Cable length stated in the parts list is 53". That figure is jacket length, not overall cable length.

The cable is well and truly seized; no doubt it's utterly beyond salvage.

- - -

Enable/Kill Bail Cable Update -- WEDNESDAY, MAY 15, 2019

I clamped one end of the old cable's jacket in my vise, and attached a slide hammer to the other end's 'Z' fitting in an attempt at getting the cable to move in its jacket. One good whack with the slide hammer finished off the cable for good -- the cable came apart from a rusty point inside the jacket, like so.

The exposed ends of the cable look fine, but inside the jacket the cable has rusted. That's the inevitable fate of any jacketed cable on machinery that's not kept under a roof when not in use.

I got a new cable. The part number is unchanged, but the cable's upper fulcrum point has been revised.

The old cable is at the left in the above photo; the new cable is at the right. It seems that the old stud-and-clip style was failure prone.

- - -

Starter Cord Handle Perch -- THURSDAY, MAY 16, 2019

A 1/4"-20 screw eye makes an ideal perch. I've replaced the ragged old handle with a new spare that I had on hand.

- - -

Fuel Tank Removal

The fuel tank lifts off of two slots at the rear of the cowl. A spring-type hose clamp fastens the fuel delivery tube to the tank's output nipple at the left side end of the tank. Here's a view of the fuel tank separated from the engine.

I'll empty the tank of what little fuel there is in it. The tank can spend the night by the furnace to thoroughly dry out.

Air Cleaner

A clockwise 1/8 turn of the air cleaner's shell frees it from the carburetor. The filter element inside this air cleaner is in appalling condition. (A new filter element is P/N 36905.)

This mower must have never received a stitch of maintenance.

- - -

Cowl Removal -- TUESDAY, MAY 14, 2019

[Carburetor removal will be much easier with the cowl removed.]

• One 10-32 x 1/2" special shoulder screw at the oil filler tube's neck, at the right side of the cowl -- hex washerhead, 5/16" A/F.
• Two 10-24 x 9/16" hex washerhead screws with captive external tooth lockwashers at the front, 5/16" A/F.
• Two 1/4"-20 x 1/2" hex washerhead screws at the rear, 3/8" A/F.

Lift the cowl straight up off the engine. That gets one to here.

Carburetor Removal

• Note/sketch the position of the governor link in the throttle lever.
• Disconnect the crankcase ventilation tube from its nipple at the top of the carburetor.
• With a 3/8" and a 7/16" wrench, undo the two nuts and bolts holding the carburetor to the intake tube. (The inboard nut and bolt are very awkward to deal with. The 3/8" A/F bolt head is impossible to get a wrench on. For the 7/16" A/F nut, you'll need a box end wrench.) Mind the gasket. If the gasket is stuck fast to either the intake tube or the carburetor, that's fine. Just leave it be.
• Unhook the governor link from the throttle lever.

Here's a view of the carburetor off the engine.

The fuel delivery tube is 1/4" I.D., 7 1/2" long.

- - -

Carburetor Teardown -- WEDNESDAY. MAY 15, 2019

Here's the air cleaner mounting plate off.

Mind the ring gasket.

The two special shoulder screws are 10-32. Their hex heads are 1/4" A/F, with No. 2 Phillips recesses.

Here's the float bowl off.

The main well nut's hex is 1/2" A/F. The float is plastic. Float level is adjustable by bending a tang on the float. If the float is level when the inlet valve is closed, that's about right. Not shown is the resilient inlet valve seat. That can be had as part of the repair kit, along with a new ring gasket for the bowl. Everything on this carburetor appears to be in pretty good condition; I won't bother with a repair kit.

- - -

And here's the primer bulb off.

It's quite an elaborate primer bulb arrangement. There's a spring-loaded white plunger that operates in concert with the bulb. Here's my best interpretation of primer bulb operation:

First off, a word about the red tube sticking out of the front of the carburetor -- I suspect that's there to afford a slight pressurization of the float chamber. In-rushing air will enter that tube and proceed to the float chamber via the priming chamber. Normally, the white plunger is kept from seating by its spring, so keeping open the air path from the red tube to the float chamber.

Pressing the primer bulb results in the following sequence:

• When the bulb is pressed part way, the white plunger seats and seals off the priming chamber from the atmosphere; i.e. the red tube's opening.
• Pressing the bulb further slightly pressurizes the float chamber, sending a dollop of raw fuel up the main jet and into the throat of the carburetor.

The pushnut that retains the primer bulb can be coaxed out with a mechanic's pick. A new primer bulb with a new pushnut is P/N 36045A. Here's an old post that I wrote about Tecumseh primer bulbs.

Note that aside from float level, there are no adjustments possible on this carburetor. Both the idle and the main jet orifices are fixed. There is no idle speed adjustment screw; the engine only and always runs at governed speed.

- - -

Governed Speed -- THURSDAY, MAY 16, 2019

It appears that governed speed is not meant to be adjustable, but it can be adjusted by bending the governor spring's anchor post located at the intake pipe.

When I first got the engine running, its governed speed seemed to be a bit leisurely. Governed speed is determined by the tension on the governor spring -- increased spring tension results in higher governed speed. Accordingly, I bent the spring's anchor post forward a bit to increase the spring's tension, and get a governed speed of roughly 2,700 rpm. The engine sounds about right at that speed -- neither too slow nor frantically fast.

- - -

The mower is now running fine. The primer works, though that primer bulb arrangement seems to me to deliver pretty lame priming. A cold start can require a lot more than just three pushes on the primer bulb.

I've sort-of sharpened and balanced the blade. I've ordered a proper blade balancer and a set of grinding stones from Amazon. When they arrive, I'll return to the blade and see if I can improve on it.

- - -

Update -- MONDAY, JULY 8, 2019

Both the blade balancer and the grinding stones turned out to be a bust. The balancer was poorly thought out and poorly made. It couldn't be relied on to give an accurate balance indication. I returned it for a refund. The grinding stones were unbelievably bad. The shanks, which were advertised as 1/4" diameter, were actually 6mm diameter -- useless. The stones were poorly mounted on the shanks -- ridiculously wobbly and imbalanced. I complained to the vendor and got a refund without having to return them. So, I'm back to the few marginally serviceable stones that I do have.

The mower's deck has some rust-through in places. That doesn't bode well for a resale. I have the use of a pressure washer for a while, so maybe what I should do is strip down the mower to the bare deck, pressure wash it and see what I have to work with. I'd like to get the mower in fit condition to sell, especially since I've already gone and sunk a new control cable into it. This may be futility at work, but what the hey; it's not as if I have any job interviews lined up. (Actually, if I were to attend a job interview at this stage of life, I'd get my kicks by telling the interviewer exactly how much I care about shareholder value, in forthright and earthy language.)

- - -

Nope

I just went and took a closer look at the mower's deck, and it's a write-off. There are a lot of spots where rust is bubbling up under the topside paint, and those spots are easily punched through with a screwdriver blade. There's no point in pursuing a restoration. (I could have seen that coming right from the get-go. This hasn't been my shrewdest piece of work.)

So, the mower can languish under a fir tree at the bottom of the yard. Maybe a mower will come along with a good deck and a seized engine, and I can cobble together a good mower from the remains. Else the thing can go for scrap. We'll see.

- - -

Update -- FRIDAY, OCTOBER 11, 2019

For want of anything better to do, I decided to tear the machine down to its bare deck, and see about patching the rust holes and repainting it. Here's the deck with the engine and handlebar off. The deck's been pressure washed.

- - -

Front Wheels And Height Adjusters -- MONDAY, OCTOBER 14, 2019

The front wheels are nominal 7" diameter x 1.8" with a 1/2" bore. The wheel retaining nuts are 3/8"-16, 9/16" A/F nylocs.

Here's a view of a front height adjuster with its wheel removed.

That big hex is the head of a special shoulder screw that's 3/8"-16 at its inboard end. To remove a height adjuster requires a 9/16" and a 15/16" wrench. The assembly may be very tight. You may need to use on impact wrench on the 15/16" hex.

Note that there's a steel baffle that is unfastened once the height adjusters have been unfastened.

- - -

Rear Baffle -- TUESDAY, OCTOBER 15, 2019

There's a black plastic baffle inside the rear of the deck that must be removed for access to some of the rear height adjusters' fasteners.

The baffle is fastened in place by two 1/4" x 1" pan head threading screws (T30 Torx recess) underneath the rear chute door. (Unhook the rear chute door's two torsion springs before proceeding.) Remove the two threading screws to remove the baffle.

- - -

Rear Wheels And Height Adjusters

The rear wheels are nominal 8" diameter x 1.8" with a 1/2" bore. The wheel retaining nuts are 3/8"-16, 9/16" A/F nylocs.

Here's a view of a rear height adjuster with its wheel removed.

The rear height adjusters are fastened the same way as the front height adjusters, but each adjuster has an additional fastener -- a 1/4"-20 x 5/8" hex washerhead threading screw, 3/8" A/F.

Note that the height adjusters are also the mounts for the rear chute door and the flap. the flap's hinge rod is swaged at each end, so the rod doesn't want to come out. I ground down the swaging at one end of the flap's hinge rod like so, so I could remove the hinge rod and flap.

Later, I'll drill through that flattened end of the hinge rod to accept a small cotter pin. That will restore the hinge rod's retention.

- - -

Flap Hinge Rod Drilled For A Cotter Pin -- SUNDAY, OCTOBER 20, 2019

Here's the ground end of the hinge rod drilled through 1/16" diameter for a 1/16" x 1/2" cotter pin.

Now I have hinge rod retention back.

- - -

Deck Rust Holes Repaired, Deck Painted And Reassembled

The paint I used is Krylon Dual Superbond, satin burgundy colour. The stuff doesn't cover very well. It took three coats to get a reasonably uniform colouration thoughout.

- - -

And here's the machine back to operability.

It still needs a new spark plug, air filter element and control cable. For now, it can go spend the winter under its tree at the foot of the yard. Come spring I'll finish it up and see if I can unload it on Kijiji. If I break even, I'll be happy.

- - -

To be continued.

# # #

FEEDBACK

# # #