Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

  I’ve got a few questions on rebuilding a small engine.  The engine is a Tecumseh HSSK50 67366S.   I think the model year is 1998.  It came off an MTD Gold 526 snowblower and had a broken rod.  The exploded parts view is here:

 

http://www.outdoordistributors.com/pdf/Tecumseh/TECUMSEH-MODEL-HSSK50-67366S-PARTS-LIST.pdf

 

   I’m just experimenting to see what’s involved with doing some repair on engines and this engine was broken and free so a good candidate.  If I mess it up in learning it won’t be much of a loss. 

 

Question 1:

  After taking off the head I tried to move the piston back and forth with my fingers.  It seemed tight and did not move from side to side.  The reading I’ve done says to measure the space at the wall.  I assume they meant the ring to wall distance and not the piston to wall distance. 

    They mentioned taking a reading of the gap but did not say how to do that.  How do you take a measurement of that distance? You can’t use thin flat sparkplug feelers as they’re too stiff to bend with the wall shape.  They would press out so not give an accurate feel.  How do you measure the ring to wall gap?

 

Question 2:

   What are acceptable limits for the gap?

 

Question 3.

   I don’t have a dial gauge that can take an inside reading of the cylinder.  I have dial calipers but I don’t think they would be accurate enough.  There may or may not be a ridge at the top of the wall so the calipers would read the ridge and not be able to get deeper.  Is there a way around this without having a special gauge for taking the reading?

 

Question 4:

   Given that I don’t have gauges for an inside wall measure would it be unreasonable to assume a 10 year old motor would be worn and just put in .010 oversized rings?  Lightly hone out the cylinder wall and go with .010 rings? 

   Just say the motor was lightly used and the wall in excellent shape.  Would putting in .010 rings cause problems by being too tight?

 

Question 5.

   On opening up the case I looked for timing marks.  I think one is a hole in the cam gear.  I did not move anything before taking out the crank and cam.  I could not find another mark on the crank gear to mate with the hole in the cam gear. 

   I should have made some scratches but did not for some reason.  I think I got a phone call and forgot when I got back.  Does anyone know the marks on this engine?  My reading said to look for a raised dash or one of the teeth on the crank gear to be beveled.  I could not find either or any other mark.  How can I get the alignment right?  I could put it back together with the case open and hand turn the crank and watch the valves but I think I might be off a tooth or two doing it that way. ??

 

Question 6:

    The crank journal (the place where the piston gets bolted to the crankshaft) looks shiny and without scratches.  The piston and rings look undamaged.  The valves and tappets look fine.  There is no place inside that seems to have gotten hit by the broken rod end or the broken bottom part.  The only place that got scratched was on the crank.  That was big bulging part I think is a counter weight for the crank.  It got scrapped quite a bit over a few inches but I don’t think there’s been enough metal removed to make a difference in weight so seems like that damage would not factor in. 

   Given that all the parts seem ok if I were to bypass putting in rings the minimum repair would be putting in a new rod and at least cleaning and lapping the valves.  The minimum job would be doing that and putting everything back in and torque what ever needs to be touqued.   Does that sound right?

 

trouts

Sorry, Wireless keyboard locked up as I was typing and went into all caps....

Well,

I would check the valves at full open, I would see if there was any excessive wobble in them.. (checking for bad or worn valve guides)

Also check the looke of the stems when you have them out..  (check them for a wear on the stem, like a a ridge at the travel limits where they ride in the guides).

Check the piston pin for the same effects and wear as you would a crank journal.

Look at the oil residue in the engine case,  Is it grey and shimmer like aluminum putty?

My bet is the engine only needs a rod and a rinse out with solvent  (seals and gaskets also).  But if you are in there you may depending on wear, install rings.  I wouldn't change the piston unless i found other things wrong with it.

I believe this engien was running strong when it threw the rod, or it was worn out.   (is there thick carbon?, aluminum putty or grit in the / oil residue, do the valves rock far back and forth? does the engien have a groove on the cylinder wall that would make me stub my toe?)

It comes down to one or the other:  Did it die a slow death and the rod was the final straw over 10 years of heavy use or did it seize the rod from a one time event of low oil?

Good Luck,

Friiy

P.S. If you are truely trying to learn, I would just clean it , put a rod in , then see how it works.   Put it back together and see if it has problems.  Watch results as each problem (if it has any) is resolved one at a time. 

hey troust2

first thing filly gave some really good adivce , as far as checking to confrim if u have the correct timing question #5 when u have the cylinder head off and the valves are back in turn the engine over and watch the valves too see if they both open slightly at the same time (exhuast stroke ending/ intake stroke starting). if u have an engine that has the head off u can check it and see what l'm talking about.

good luck on rebuild

friiy and niper99

The case was looked over before and seemed ok but today when doing the detail cleaning of the last drops of oil I noticed a gouge on the inside case wall. On the outside there was a hairline crack about an inch long with a very slight bulge. I put water on the inside and it leaked through so I assume the block is hosed.

So much for that one but I might try putting what's left back together for practice.

I've got 3 other bogus engines. Another 70's 5hp with a broken rod and two older 7hp's. The 7hp's are the ones I really would like to fix and the 5's practice engines.

The 7hp's push oil so still functional. One has 90psi but pushes droplets of oil out the breather. The other does not push oil until it's run for a while and then under load. At that point it gushes oil. The breather mesh filters on both of those are clean so I suspect rings or valves on those.

The goal was to get familiar with things on the 5hp then do the 7's. The first 5hp is out. I might as well take the second 5hp with a broken rod apart as practice and if it's in good enough shape put a rod in that one. If that goes well then work on the 7's.

Thanks for all the information and suggestions. It's excellent reference information and will help quite a bit on the next engines.
trouts2

Hey Touts,

There realy is not any structure to the area of the brake/crack all the load is in the webbing of the case where the crank fits through.

I would   "stop drill"  the cracks of case and fill in with a good epoxy.

God Luck,

Friiy

I have some great aircraft struckure epoxy called 1830g, If you like I will send you some.

   Thanks for mentioning the epoxy.  I just might do that.  The engine looks-wise is in excellent shape.  There’s no rust rash around the head bolts and the cowling and recoil look new.  I looked pretty close at the insides and I think the damage is only in that one spot. 

 

   The other 5hp was taken apart today.  It also had a broken rod.  The case on that one looks intact.  There’s one gouged spot but no sign of puffing out the case or cracks.  The crank journal on this one is all chewed up and the piston skirt off in chunks.  From what I’ve seen so far the case should be salvageable but would require at a minimum rings, piston and rod.   I just finished up taking it apart so tomorrow will do the refined cleaning and take a better look at everything.

 

   I compared the piston on both 5hp’s, the newer 5 versus the older 5.  The new 5 had a larger diameter piston.  Its rings were not as thick.  Its piston skirt was not very long and the bottom cut parallel to the piston top surface.  The older piston had the skirt extend down past where the new one was cut off as in an extended v in two places.  The cross pin that holds the rod was smaller than the older pin and on the new piston inset into the side diameter so less metal in the pin and less in the piston body.

    So the newer piston was larger diameter but less overall metal so lighter.

 

    The cranks were also different.  I’ll try to post a picture.  The newer one was shorter and lighter.  The cam gear was much smaller on the new 5 and the counter weights also much smaller. 

 

    Given all that extra weight rotating at 3600 rpm there’s got to be more torque in the older motor.

 

     The older 5hp came on a Jacobson Imperial 526 which is an odd size these days.  It might be nice to get this one working again.  The engineers should have sized a motor capable of good performance so I expect this engine if in good shape might toss snow well. 

   The body paint is all gone and the machine completely covered in surface rust but the metal all solid.  The tractor insides are unworn and tight.  The friction disk looks new and unused.  It’s wider than any I’ve ever seen and thicker than either Ariens or Toro rubber from the 70’s.  The scraper bar seems original and without wear.  It would be nice to see this thing run so maybe I’ll give this motor a shot if there’s nothing else wrong with the motor.

     The cams were compared and the cam from the older 5hp is significantly heavier than the newer 5hp crank. 

    The engines are covered with dirt and oil so pretty messy and not so easy to clean.  Below is the poor man's cleaning tank made up this morning for cleaning the 5hp.  It's a 5 gallon plastic gas can with the top cut out as a splash shield.  Put the parts inside which get cleaned with gas and a paint brush.  When done the gas is poured back into a spare 1 gallon gas can for reuse later.  The dirt and grime left on the bottom is cleaned out with a rag.  It worked out pretty well.  The parts get clean with only a film of oil and gas which cleans off easily with warm water and soap.

trouts2

Hey Trouts2,

The epoxy I was talking about is 1838 b/a green by Scotch-weld...good stuff..

Your 7 hp that blows oil from the breather may have a problem with the ring gap.

I have seen rings that spun in their groove and lined up with each other,  meaning that compression and exhaust blowby is maximized,  or you may have a compression ring that has stuck (carboned or seized ) in the groove compressed (making it in-effective)

OR... you may have a breather assy. that the reed valve is loose or stuck part open.  (try swapping with another breather assy.)

If you need piston/ ring assy. on a TEC. motor.   I like to use the aftermarket company Rotory Corp.  for those kits.   they made taking in older engines that need rings more cost effective for repair.

Good Luck,

Friiy

trouts

That engine looks like it burns a little oil...

The black spot is just a hot spot on the cylinder wall next to the exhaust valve,  a little burned/ glazing oil there.. (just break it up if you hone the engine).     

I have seen people bust the breather by sticking their finger in the hole and bending the reed valve out of limits.

the rod I check by checking for a knock when its running under heavy load, if the engine is apart I torque the rod to the crank and check for play. I would not change the rod unless I found a problem.

The staining of the case around the valves where the head gasket sits is a leak,  sometimes the engine will make a "chirping noise" when cold, the chirp sometime goes away wen the engine heats up, but the leak is still there..

Rotory is a dealer supplier, if you can find a dealer  you may be able to save a little more.

Your 5 hp with the scored crank,  I bet 50/50 the crank is good,  the crank likely has aluminum melted on it, (kinda like crayon wax on a smooth wood table).  the way to remove it without damaginge the crank is to use pool acid (muratic acid....spelling?)..   take  a Q-tip and dip it in the acid and wipe it around the area of the crank surface, if it is  aluminum, the area will turn grey and bubble, repeat until clean and smooth.   Do not let the acid stay on the metal any longer than needed.  Overnight acid will start to cause surface rust  (even the fumes),  so apply the acid by hand,  rinse with water, then spray the crank with  oil or wd-40 to displace water and prevent rust.

If they wan't to sell you only packs of 6, let me send you one pack and you can see if you like it.. (epoxy). Email me with your info/address

Good Luck,

Friiy

Friiy,

   I finally got around to picking up some Muriatic acid and working off the aluminum smudges on the older 5hp crank.  It’s looking pretty good and I think smooth enough to be used again.  I can’t feel any bumps or depressions or see any imperfections.  It got a light finish sanding with 600.  Thanks for suggesting the process.  I thought it was unsalvageable after first looking at it.

  

   The above motor requires a rod, rings and piston so somewhat expensive.  There are two other motors here waiting for parts and tools which I’ll probably try first.  A newer 5hp which needs rings and rod and a older 7hp which just needs rings.  The experiment candidate is the newer 5hp so if I goof up it will be less expensive. 

 

  By the way the newer 5hp crank weighs 3.69 and the old 5hp 4.77.  Quite a difference. 

 

  The rest of the parts and tools should be in by the end of the week so maybe in two weeks I’ll have a couple engines done and tested. 

trouts

Stumped again.

 

   The original ring set has been replaced with a new set that adds some features.  The old compression ring did not have an internal notch or bevel on either ring.  The new compression ring does.  That seems ok.  The oil wiper ring (second ring) has a stepped notch on the outer face and that also seems ok.  Both match the book I got from the library but the original old rings don’t (no bevels or notches on either ring).  I think the new set is Tecumseh’s updated replacement set and ok.  The ring set is 40006.

 

    The problem part is the third ring.  It’s a very different design that the old ring.  The old ring was one piece with cutouts for wiped off oil to go to the crankcase.   There’s an expansion ring behind it.  The new ring is a very different design with a top and bottom ring and also a spring ring that goes between them. 

 

    What I’m not sure about is if the new design eliminates the need for the expansion ring.  There are two issues. 

1.       Should the expansion ring be used with the newer style oil return ring (third ring)?

2.      If it should be used, given it’s age and I think spring steel then is it always replaced or just used again?

 

   It’s confusing because the way my book reads the expansion ring is something that would be inserted when the motor was getting old and the oil return ring might need some help being pushed out.  I did not expect to find one in a motor that had never been opened before. 

trouts