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

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

Hey Trouts,

You should not have to use any rings or ring parts over again.   The new rings are just better for oil control and completely diffrent..    Did they send a picture or piece of paper showing the correct orientation of the new rings? 

Be sure to clean the ring grooves if you reuse the old piston (a piece of a old ring ,ground flat , to drag throught the groove and remove carbon).  Be sure to put the piston and rod back in its original orientation.   If you did not mark them, check that PDF file that Dennis put  a link to. 

Good Luck,

Friiy

  The ring set was a Tecumseh set and did not have any paperwork in the package.

   The manual you mentioned I think was the Tecumseh 3-11hp engine manual.  It has a good explination of the bevels and notches and their orientation on the piston.  The compnents have been cleaned up so ready to install. 

trouts

  Got it back together but it won’t fire up.  On the first pull it gave one cough and belched some smoke and would not fire again.  I took the head off and there was oil on the gasket, block and head surfaces by the gasket.

 

   The gasket looked good and the head flat except for some slight curl at the very edges of the head and block.  I fine filed those off and the head and block seem flat – at least with the straight edge I have held to the block against a light. 

 

   I buttoned it up, torqued the bolts to 200, and putting some talcum powder around the block and head joint.   On pulling the start rope it blew away the talc at the gasket at the middle side head bolt.  The head must be warped.  It leaks from the side.

 

   The engine had a broken rod so ran before the parts were installed.  All I can think of is the rod must have pushed the piston into the head.  There’s no sign of any contact though so puzzling how the head or gasket could leak.  ?? 

 

1. Is it common that a head would be warpped after a rod breaks?
2. Getting it machines would be to expensive.  Is it possible to get it within service tolerance (what ever that is) by hand?  Can it be flat filed or ground on a flat plate.  A friend made a plate for me 17 x 17 inches flat across the diagonal to a 10 thousandth.  The gasket seems to hold at the valve and cowling ends but bowed up in between. 
3. How can I deal with this?

trouts

trouts2 wrote:

trouts

did u check compression?, is the head gasket new or old ? l personally have never seen a head warp badly enough that a new head gasket wont fix.

I have never seen a head warped to care about.  

Do you have a piece of the old gasket stuck on the edge somewhere?

Are all the bolts for the head the same size?  Sometimes there are three or more bolts longer around the exhaust valve too draw and dissipate heat in the block.. If these bolts are installed in the wrong spot they may bottom out before tightening the head.  Also are your threads clean in the block?  Maybe you are trying to drive these bolts into dirty packed treads  (  burned up oil grissle)  not really seating against the block with the gasket...

Are you using a old gasket?  The lead plate head gaskets seal great, but are one use only,  ridgid Gaskets with the tin sometimes burn through..

The new gasket sould be able ,I imagine, to take up .025 " easy,   they are very thick..

All I ever did was clean the head and block surface with scochbrite to take the carbon/ old gasket pieces off... I never cared to even too see one warped,  (it never mattered,  the gasket always held...)

Later, Good Luck ...   I gotta go back to work,   Gotta broke RB211,  need to look up parts.

Friiy 

   The flywheel key was broken and the flywheel at exactly 180 out.  After testing since it was 180 out I figured I had the cam in wrong.  On starting to unbutton the engine I found the broken key. 

 

   After putting in a new key it starts, runs and seems to be fine except it runs away.  The governor is not kicking in.  I don’t know how that can be as there’s only an arm and I think it just butts up against the wheel weights. 

   The arm is toward the inside of the case which I think when under spring tension would snug the arm against the governor wheel on the side towards the back of the case.  ?? So I’ll have to check what up there. 

 

   It seems like the arm is not being moved so possibly on installing the cam the arm got out of place and toward the cover side of the engine but if that were the case the outside part of the arm would almost hit the carb the way things are setup on this motor.   It could be I have the linkage positions wrong.  I have a couple of similar motors so will check the linkage on those.  So it runs away but I could test it by working the throttle.

 

Niper99 – I took a compression reading before I tried starting the engine and it was about 115 so the leak a puzzle i.e. decent compression with a leak.  But that has happened to me with a leaking sparkplug.  I got 90psi but could not start the engine due to the plug threads leaking.  I don’t know how I could get 90 unless the rubber from the tester was enough to seal the leak. 

 

   The talcum powder test was false.  The muffler gasket broke and I did not have a replacement.  It was causing the talc to blow around.  What I thought was a line of talc removed from the head gasket seam was just talk that fell off in a line from the joint so misleading.  

 

   After a few short runs the engine tests at 115 psi.  With new rings and valve lapping I was expecting at least 130-150.  The cylinder was honed with a medium stone so possibly the psi might improve with wear.

 

   Because I thought the timing gear was wrong and going to unbutton the engine I drained the oil.  Up to that point the engine had not run and was only hand cranked many times.  The oil was loaded with very opaque gray color and the first oil to come out filled with fine suspended crud.  I’ll save that oil and tank it for later use as the first oil in another rebuild. 

 

   I’m a bit disappointed by the governor not working but that should be fixed with either getting the linkage right or opening the case again and getting the governor arm in the right position.  It sucks but minor.

 

   All in all I’m pretty happy that I made this much progress and learned quite a bit.  The next engine will go much smoother.  Thanks for all the help.  It’s really appreciated.

trouts

  The glue I mentioned in other posts broke down so tiny spots of oil started showing up on the tires.  The epoxy turned to soft gum and let go so a few holes were exposed.  (The holes were from drilling into the hair line crack).  So muxh for the 3600lbs and 250 degrees rating.

 

   Since the holes and crack have to be cleaned and re-epoxy’ed  I drained the oil to unbutton the engine.  In the dregs of the oil was  what looked like a white tooth from the governor gear.  It makes sense as the governor was running away and very touchy to set.

 

    The drained oil is again very gray.  ??  Possibly something is wearing and it’s fine aluminum suspended in the oil.

If it is metal it should settle out of the oil,  maybe put it into a glass jar and watch it...

it is not part of a ground up governor gear is it (plastic)?

You can always take it apart and check for chafing,  or wear in diffrent spots.

Could your piston pin clip have come aprt and beat a little metal off your piston or cyclinder?

?????

Friiy

  Opened up the engine. Three teeth were off the governor gear and intact at the bottom of the case.  There were also a few small chunks which were I think were epoxy which melted and fell off the case side.  They broke up pretty easily with a knife.

 

   The oil was changed after a few minutes of running and put in a glass jar.  It sat overnight.  That one had the small chunks, gray, and with microscopic pieces of metal which shine when put to a light. 

   The second batch of oil had about 10 minutes of run time and sat overnight in a jar.  It did not have any chunks but did have microscopic pieces of metal but fewer.  It was darker than the first batch. 

   It could be the small flecks are from the cylinder scoring.  I did not score it much but it was with a medium stone so it could be the flecks are from that.  It might also be that there’s some normal leaking past the rings due to the scoring making the oil gray. 

  

   The cylinder wall still had the scoring but looks like it’s wearing in.  The wall seems very smooth.  There’s no missing metal like chunks broken off the cylinder skirt so possibly the flecks are normal remnants of the scoring.

 

   When the engine was running it seemed overly noisy.  I had it mounted on a snowblower frame but pretty sure all the noise was from the motor.  I listened to it with long screwdriver and could not hear any grinding inside. 

 

    The governor gear assembly is about 10 dollars so cheap enough to give it another go.

trouts