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

Followup on the rebuilds.

   The 5hp with the cracked block is finished and running very well.  Currently there is PC-7 in the cracked area with about 20 minutes of run time with the glue holding under heat so far so good on that part.  The motor is running very smoothly.  This motor had broken governor which I missed during the initial buttoning up.  The rod or a piece of the rod hit the flyweight and teeth on the governor assemble breaking the plastic governor gear.  There were long delays getting the assembly off it's post and getting a new one.   So the 5hp is running very well and the glue holding so far.  If it fails I'll take it apart again, clean everything and re-glue with I think it's JB-Weld.  The big deal for me is the rebuild part went very well.

  During the delay a 7hp Toro that was pushing oil was rebuilt and that one went very well.  It got rings and a valve job.  All the internal tolerances were to spec with the Tecumseh L-Head manual except the cylinder bore which I can't measure. 

   Also finished after delays was a Tecumseh 8hp which got rings, rod and a valve job.  The governor arm was not moving and controlling high speed so I took it apart and inspected everything.   Everything was ok in there and on putting it back together the governor responded properly so a mystery.  I don’t see how that was possible because there’s no room in there for the governor gear to be anyplace but in it’s proper place and weight able to move.  ??  Anyway I put the cover back with just a slit of an open space and a flashlight shining in to verify the govern gear meshed properly and then buttoned it up. 

   This all has been a great experience for me and very enjoyable.  I’ve had a lot of questions on this thread and a couple of others with related questions and appreciate the all the helpful advice.  When I started out I never had a concept of rings (plural) and the function of the distinct ring types.  By the way, Friiy, I never got a paper with the ring sets until the third set of rings cam in which explained the ring types and groves which by that time I was aware of.  If that paper came with the first set it would have solved a lot of questions I had. 

   The rebuilding was enjoyable, done in the cellar on my spare time watching TV and will give a few snowblowers an extension on life.  I’ve got two more motors with problems and will be doing those in the cellar during the Olympics.   As a note Harbor Freight opened an outlet close by and offering a 6.5 hp OHV engine with a cast iron bore for $129.  These motors have fantastic reports  on the net and an alternative to rebuilding. 

Thanks for the help:

Trouts2

Sounds like a lot of good news.  Before you buy one of the Harbour Freight engines make sure you can get parts for it...

Now Harbour Freight  also sells some models of Briggs and also Robins. (both good).   But the Chen  Wen, or what ever is...  IS from what I hear impossible to get parts for..  the Robin is hard to get parts for..   It looks like Honda, part for part but is made cheaply in China and they rattle apart over time.

Good Luck,

Friiy