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

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

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. 

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

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 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

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.

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