Monday, May 20, 2019

A Small Engine Spark Tester

I got fed up with gimmicky spark testing apparatuses, so I came up with this.

It's an 18" length of wire with an alligator clip on one end, and a battery terminal post clip on the other. The alligator clip is big enough to clip onto an engine cooling fin or whatever for a ground connection. The battery terminal post clip will fit any spark plug's body.

Here's a view of the tester connected on a string trimmer.

In the above photo, the cooling fins are inaccessible, so the ground connection is made at the carburetor's idle speed adjustment screw.

The tester works nicely. It's best to have the machine under test inside a darkened workshop, where you can be certain of seeing the spark if there is one.

Some lawn mowers can be awkward for positioning the spark plug so it's visible. At times, you may need an assistant to observe the spark plug while you yank the starter cord.

Anyway, it's 'farewell' to gimmicks like this thing.

And 'hello' to reliable spark testing.

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Sunday, May 19, 2019

A Canadiana 20" Lawn Mower

It's a basic 20" mower with wheel height adjusters. When I first tried it, it started on the first pull. Then it wouldn't start. Then it started on the first pull again. Then it wouldn't start. 'Not a condition that one could put up with.

Here's a shot of the ID label.

I have no idea what "HOP" stands for.

Engine is a Briggs & Stratton 300 Series, 148cc. Model 9L602, Type 0009 F1, Code 13012251. DOM JAN 2013.

- - -

The mower appears to be in fairly good condition overall. The engine has a tall, 1/4-turn fuel tank cap that I've not encountered before.

- - -

Enable/Kill Bail Cable

The enable/kill bail cable has a laceration that refuses to photograph well.

There's also a bit of a kink in the cable. In spite of that, the cable works smoothly. I would like to repair the jacket's laceration, though. A 1/4"-20 coupling nut split lengthwise, and a couple of small hose clamps may be the solution.

There's what appears to be a part number embossed on the cable's jacket -- "440934".

Enable/Kill Bail Cable Update

Here's the cable's jacket laceration repaired.

That looks good. I've mostly gotten the kink out of the cable, and the cable still moves freely. That should be a long-lasting repair.

- - -

Spark Plug

The spark plug has one of those big, clunky, shielded connectors on it.

I've seen that before. I'd love to know what that style of spark plug connector is all about.

The spark plug is a Champion RJ19LM.

It's a 14mm plug with a 13/16" A/F (across flats) hex. Gap is 0.030". It looks to be in reasonably good condition.

- - -

So, 'time to remove and dismantle the carburetor/fuel tank and see if anything is amiss there. There's some evidence of water in the fuel tank. It may be that all the engine really needs is a fuel tank flush and dry-out, and fresh gasoline. We'll see.

- - -

Air Cleaner

The filter could stand some attention.

Yikes! That's more filth accumulation than I'm accustomed to seeing on an air filter. The machine's been neglected.

Governor Link/Spring

It's a little different from what I'm accustomed to seeing on Briggs & Stratton engines.

It's a fixed speed governor -- there's no speed adjustment lever. And there's no air vane. This engine has a mechanical governor like Tecumseh engines have.

- - -


'Found nothing untoward, except for a badly stretched diaphragm.

'Replaced that along with its gasket. 'Cleaned and flushed the fuel tank and the carburetor. 'Put it all back together and the mower starts and runs fine.

- - -

To be continued.

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Friday, May 17, 2019

A Murray 20" Lawn Mower

Model No. is 7800325. Serial No. is 2013045351.

Engine is a Briggs & Stratton 475 Series, 148cc, Model 9T702, Type 0118 B1, Code 0804075.

- - -

It's a nice little basic lawn mower that's been 'worked' on, to no good effect.

The enable/kill bail and cable are missing altogether. The kill switch and brake have been deleted from the engine.

An atrocious installation of a toggle switch for a kill switch has been done.

The muffler has been tampered with for some reason.

The screws are loose, and the anti-loosening bar is out of place. Why on earth anyone would fiddle with a perfectly sound muffler on a small engine is beyond me.

Anyway, the engine won't start. 'Time to check for spark.

Spark Plug Connector

This is a new one on me.

A big, clunky, shielded spark plug connector. I think it may have to do with electromagnetic radiation suppression.

Spark Plug

It's a Champion RJ12C. Hex is 13/16" A/F (across flats). Gap is 0.030". The plug appears to be in quite good condition. Let's see if we have spark.

And there's spark. The engine can be made to run.

- - -

Spark Plug Update -- SUNDAY, MAY 19, 2019

It dawned on me that the RJ12C can't be the correct spark plug for this engine, owing to the fit of the shielded connector. The metal shield on the connector is supposed to reach down to and contact the hex on the spark plug. On the RJ12C, the ceramic is too long for that to happen.

- - -


The loose muffler must be attended to. Here's a view of it off altogether along with its fasteners.

It's a large muffler. I take it that Briggs & Stratton have really made an effort to quiet their engines.

The screws are special shoulder screws, 1/4"-20 x 2 3/8". The threaded portions are 1/2" long. The hex heads are 7/16" A/F. I'll reinstall the whole affair with anti-seize compound on the screw threads.

- - -

Fuel Tank

There's some fuel in it. I can see little globules of water down in the bottom.

I've cleaned and rinsed the tank with solvent, and left it by the furnace to thoroughly dry out. I may take a hair dryer to it to see if I can get it dried out quickly.

Governor Vane

The governor vane was sluggish. It was binding because its mounting base (the top surface of the coil's laminations) was dimpled. I filed down the length of the vane's pivot sleeve a bit, and reinstalled the vane. Now it's fine -- it pivots freely.


'Cleaned and flushed and blew it dry. The diaphragm looks marginal. I'll try reusing it and see how it goes.

- - -
It Starts And Runs

Fresh gasoline in a clean tank and carburetor and away it goes.

Now I have to decide how much to put into this machine regarding the enable/kill function. I'll seek my son's advice.

- - -

To be continued.

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A Homelite TrimLite String Trimmer

Here's a view of the ID label.

It's a machine that's been written off. It was given to me as a parts machine by the proprietor of the small engines shop that I frequent. I'll see if I can get it going.

Following are the problems I know about so far:
  • The fuel uptake tube is a ruin that must be replaced. The return tube may as well be replaced too.
  • I took the bump-feed spring to repair a Homelite UT 20704 string trimmer. I'm left with a kluged spring that won't work, unless I can modify it successfully. The bump-feed bumper is almost worn through.
  • Compression feels abnormally high. From experience with a pocket motorbike engine, that may indicate a stiffened piston ring. We'll see.
Anyway, let's see if we have spark.

Spark Plug

It's an NGK BPMR7A, and it looks pretty fouled.

It's a 14mm plug with a 3/4" A/F (across flats) hex. Gap is 0.025". I'll clean it up and do a spark test.

- - -

I've got spark.

- - -

Compression Test

I did a compression test while I had the spark plug out, and the gauge registered 110 psi! That's remarkable compression for an old engine. The engine's 'pull' feels normal with the spark plug out, so I guess the piston rings are ok.

- - -

Carburetor Removal
  • Air cleaner cover off. Air filter element removed.
  • Fuel uptake and return tubes slipped off their nipples. Mind/label/note which tube goes where.
  • Two 10-24 hex nuts, 3/8" A/F.
  • Pull off the air cleaner base. Let it dangle by the kill switch wire.
  • Pull off the carburetor and unhook its throttle cable 'Z' fitting. Mind the gasket.
Embossed on the carburetor's body is "C1U 163H"; that's the body type. Etched on the carburetor's body is "H60E 5ZA"; that's the model number.
Metering Diaphragm And Needle Valve

Note the following:
  • The two screws are M3 x 6mm, No.2 Phillips recess.
  • The metering diaphragm gasket goes directly to the carburetor's body; the diaphragm goes to the cover.
  • The metering diaphragm must be supple. Stiffened diaphragms are a common fault. A stiffened diaphragm will render the carburetor inoperative.
  • Exercise extreme caution when handling the tiny spring for the needle valve. It'll take off on you in an eyeblink if you're not careful.
Primer/Fuel Pump Side

Note the following:
  • The two screws are M4 x 15mm, No. 2 Phillips recess.
  • The diaphragm goes directly to the carburetor's body; the gasket goes to the fuel pump block.
 Mixture Needles

A 'Pac-Man' tool works to get the needles out. Note and record the number of turns it takes to close the needles before removing them. At reassembly, set the needles as they were to get going. Odds are that further adjustment will be needed.

The shorter needle at the left above is the main jet's needle -- the one nearest the choke.

The longer needle at the right above is the idle jets' needle -- the one nearest the throttle.

Fuel Line Tubing Replacement

[The following is from my post about the Homelite UT20704, where I had the fuel tank off the engine. Fuel line tubing replacement can be done with the tank in place, though. That's how I actually did it on this TrimLite.]

The factory installs the tank's tubes by squeezing them through undersize holes. The same thing can be done in repair work; you just have to obtain the correct size of tubing.

The tubing holes in the tank are 11/64" diameter, so 3/16" O.D. tubing can be squeezed through nicely. The stuff to have is Tygon F-4040-A tubing, 3/16" O.D. x 3/32" I.D. Any small engines place should have the tubing. It's sold by the foot.

For a return tube, feed about an inch of tubing into the tank, then cut off a length outside the tank that's sufficient to reach the carburetor. It's helpful to cut the starting end of the tubing at an angle, to facilitate getting it started through the hole in the tank.

For an uptake tube, feed in tubing until it emerges from the tank's filler neck, where you can install the fuel filter, like so.

Cut the tubing end squarely and install the fuel filter. With the fuel filter in place, pull back on the tubing until the filter is back inside the tank, then cut the tube outside the tank as you did for the return line.

Label the tubes 'R' for 'Return', and 'U' for 'Uptake' with a Sharpie marker.

Bump-Feed Spring

I managed to kluge the kluge, and got the bump-feed feature to more-or-less work.

Bump-Feed Spring Update -- SATURDAY, MAY 18,2019

No, it's not working. String trimmer bump-feed mechanisms are diabolical. The only solution may be to get a complete after-market hub/reel.

- - -

I dropped into Canadian Tire and took a look at an aftermarket hub/reel. I couldn't plainly see how the thing could possibly fit the end of the Homelite's spindle, so I gave it a pass. The bump-feed that I have could be made to work if I could just come up with a suitable spring.

- - -

And It's Working

After an outrageous amount of mixture screw fiddling, I appear to have a working string trimmer. I'll see if I can unload it on Kijiji.

- - -

To be continued.

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Monday, May 13, 2019

An MTD Yard Machines 21" Rear Bag/Mulch Lawnmower

[Last updated: Thursday, May 16, 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.

- - -

To be continued.

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Saturday, May 11, 2019

A Toy Ride-On Motorcycle Basket Case

A roadside find.

It's a cute little police Harley that's been 'worked' on.

A six volt lead-acid battery resides underneath the saddle.

I tried charging it, but it won't take sufficient charge to power the motor. I can get the sound effects to work, but that's about it.

With the left side rear fender removed, one can see the brutal abuse that the left side rear wheel has been subjected to.

The right side wheel is ok, and it seems to be pretty sturdy. It must have taken some kind of force to so utterly ruin the pictured wheel.

So, the motorcycle is a sad piece of landfill. I'll remove the battery for proper disposal. I'll salvage what few useful bits there are. The remainder can go in a bag for the garbage pickup.

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Wednesday, May 8, 2019

An Inoperative Yardworks Garden Shredder

[Last updated: Thursday, May 16, 2019.]

My son got this shredder cheaply; it was new in its box.

As my son told it:

"Started it up and ran, but then there was a pop, some smoke and now it spins up and then stops, then repeats that cycle.

I opened it up and it seems this large capacitor strapped to the side of the engine exploded."

- - -

Hmmm. Now the thing won't even spin up briefly. It's completely dead.

There's no model number ID on the unit, only this bilingual label with what looks like a serial number.

So, let's open it up for a look-see.

Four No. 2 Phillips recess screws fasten the bottom cover on. At the centre rear, there's an M4 x 12mm threading screw, then way up under the deck there are three M5 x 14mm screws with split lockwashers and flat washers. Removing those four gets us to here.

And I discovered why the machine is completely inoperative -- there's a wire that likes to come off its terminal at the circuit breaker when the cover is manipulated. With that wire reconnected, the machine does spin up, only to shut down in a few seconds.

Anyway, the capacitor is obviously a ruin. That may prove to be difficult to source. The motor feels odd when turned by hand. There's a seemingly random turning resistance that doesn't feel right to me. Also, there are indications of there having been water incursion at one time.


Cutter Head Removal

With the hopper opened up, one has access to the cutter head. It's fastened by a single M10 x 25mm hex head screw, 16mm A/F (across flats), with an internal tooth lockwasher and a big cup washer.

The screw was installed with threadlocker; it takes an impact wrench to remove it. (Chase the female thread with a tap to clear out the old threadlocker after removing the screw. Blow out the debris with compressed air.) Here's the cutter head removed.

The hub affair looks like a fine, rugged design. (Note the rusty screw heads of the motor fasteners.)

- - -

Motor Removal

Make a sketch of the electrical connections. Disconnect the lower row of four terminations from the terminal block. Release the capacitor from its clamps.

Up top, there are four M8 x 16mm flat head screws with external tooth lockwashers, 5mm hex recess. The motor is heavy. Remove the screws with great care. Here's the motor out and up on the bench.

And now I can see what looks to me like a centrifugal brake at the upper end of the motor.

There's a hub in there that can move downward, away from two brake shoes that are integrated with the motor's frame. And that explains why the big screw holding the cutter head on was installed with threadlocker -- so that the cutter head's inertia can't unscrew the cutter head when the brake applies.

The odds appear to be reasonably good that this motor is ok -- that it just needs a new capacitor. 'Time to reassemble the machine, and see about obtaining a new capacitor.

- - -

An Inoperative Hopper-Open Interlock Switch -- THURSDAY, MAY 9, 2019

While trying out the machine, I inadvertently discovered that the hopper-open interlock switch doesn't function -- the machine will run with the hopper open.

The switch is mounted on a rectangular steel plate, and the whole affair is fastened to the shredder's frame by two M4 x 12mm pan head screws, No. 2 Phillips recess, with split lockwashers and flat washers. The wires are attached by two M3.5 x 6mm pan head screws, No. 2 Phillips recess with captive internal tooth lockwashers.

Here's a view of the switch assembly out of the shredder.

And here's the switch disassembled.

'Disassembled' may not be quite the right word here. 'Destroyed' is more like it. The body-clamping ears snapped off when I pried on them a bit. I can think of a way to go about a repair attempt, but I'm not optimistic of a good outcome.

Anyway, it appears that the switch was misassembled at the factory, and could never have worked since day one. The shorting plate and its spring were assembled in such a way that the switch was always closed.

- - -

And after a bit of an ordeal, the switch is back together and working.

I rearranged the switch's innards so that the switch could function, and wired the casing closed with 0.031" diameter steel wire. I ran a bead of CA adhesive all around the seam between the body and the mounting bracket.

I reinstalled the switch in the shredder and it's working as it's supposed to. We'll see how it holds up. Should it fail, it'll likely just have to be deleted and shorted out. The odds in favour of finding a replacement are slim to nil.

- - -

Replacement Capacitor On Order -- FRIDAY, MAY 10, 2019

Maybe this will be the cure.

- - -

The Capacitor Arrived -- THURSDAY, MAY 16, 2019

Now I see what I didn't quite understand from the vendor's description -- it's a dual run capacitor. It's two capacitors in one casing; one 40 microfarad and one 5 microfarad. These are used in air conditioners. One capacitor is for the fan motor; the other capacitor is for the compressor.

The terminals are labelled 'C', 'FAN' and 'HERM'. 'C' is for 'common', 'FAN' is for 'fan', obviously, and 'HERM' is for 'hermetically sealed compressor'. 'FAN' to 'C' is 5 microfarads; 'HERM' to 'C' is 40 microfarads. So there's my 40 micofarad replacement capacitor. The 5 microfarad capacitor will just go unused.

- - -

Capacitor Installed

It fits.

I clipped out the old capacitor and fitted out the wires with 1/4" female spade terminals. 'Clamped the new capacitor in place and reinstalled the cover.

The motor starts and runs up and keeps on running.

It remains to be seen how it behaves under load.

- - -

To be continued.

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