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

I suppose anything is repairable but would it be worth it. I can do the work myself & obviously I'd need to replace the 2 castings & conn rod & bushing, but what else would I expect to replace? crank, crank bushings, valves, piston, rings? Soon it may be up to the same cost as buying a decent used engine.

Opinions would be appreciated.

Cheers

Sixty psi is pretty low. Not sure what the specifications are for that particular engine but the engines I work on have compression readings of around 120 psi. cold engine. The first thing I'd check is the valve lash to make sure the valves are closing completely. If they're out of spec. adjust them accordingly and check compression again. if it's still low, you'd probably at the minimum need to do a ring and hone job. Depending on how many times you want to take the engine apart, you could do the work incrementally or, do it all in one shot. Top end job will need an over sized piston and rings maybe a new wrist pin & circlips. If the connecting rod is good (no lateral play) that will save work and money. How was the oil in the engine when you got it? Was it up or low?

Oil was ok, about 3/4 the way up and fairly clean.
I am concerned about honing these engines because reading through various postings here, there seems to be some concern about the hardness of the cylinder walls (aluminium) and durability. Also measuring the bore to get the right piston/ring combo seems complicated. I have rebuilt a few car engines back in the stone age (pre-electronics) so I'm not concerned with doing the work, but I'd like to get it right if I'm going to do it at all. How finicky do you need to be there?

Thanks

Are you sure that engine has an aluminum bore? I thought those old Tecumseh engines had cast iron bores? If it's cast iron, you can have it honed and possibly get by with a set of oversized rings (if such thing is available for that engine). If it's aluminum bore, I'd just put in a set of over sized rings. You'll have to make sure that the new rings will fit correctly. That will require an end gap measurement. To do that, you put the ring in the cylinder about 1/2" down from the top. Use the piston to push it down to make sure it's in nice and square. Take out the piston a use a feeler gauge and measure the gap between the ends. If the gap is too tight, you can file down one end a bit to get it right. Rings are very hard. You'll need a good file and only remove a very little at a time.

My that is quite hole in the block. I reveived an old 5 hp ariens, (1960's or 70;s) the governor was way out of adjustment. I was making the final adjustments on the governor and bang I ended up with the same hole. The connecting rod broke. Since the machine was free and very old  I put it out with a free sign. It was gone in 20 minutes. The machine was so old that you engaged a leverand the auger is always engaged. (no deadman switch) 

If I remember, correct me i f I am wrong somebody,  Tec engines go as follows H50 = horizotal 5 hp aluminum engine and bore, aluminum flywheel sometimes,  plain bearings... HM50= horizontal  5hp medium duty,  aluminum engine cast-bore,  cast iron flywheel, ball bearings.....   HH50 =5hp heavy duty , cast iron engine, ball bearings cast iron flywheel.  

    Well,  I think all the talk of rebuilding the engine is getting me excited ( not that way...)  ....

    I like the idea of doing everything 100 %,   But these engines will run forever if they are taken care of, or take alot of abuse before being rebuilt..

     The low compression could be caused by the interaction of compression release and the valve clearance being to tight... Or the there could be carbon on the exaust valve face,  or a sticking intake valve ( lagging in speed for spring  return closing ) due to gummy/ sticky fuel deposits  on the valve stem...  All this could be checked before ordering parts for overhaul..

   I would rule out fuel deposits, then spray a good penetrating oil in the spark plug hole with a needle/ straw sprayer on the valve faces , try to spray some on the valve stems of intake & exaust  valve  as you slowly turn the motor over with you other hand.   Spray the stems when the valves are open to free gum and carbon that may be present ..

Try running the motor after it soaks for a hour or so...  see if you compression has improved.  After the penetrateing oil has burned through, Watch for engine for signs of burning oil,   listen for a rod knocks.. 

If the motor seems unhealthy,  tear off the head and look for large carbon deposits from burning oil,  look for a ring ridge where the piston rings come to stop on the upstoke ( look for the ridge near the valves on the cylinder wall or 180 degrees opposite)..

Chck you valve clearance, and observe how much slop the valves have in there guides  (most older small engines were not really really tight ),  If they are sloppy pull them out and observe how much wear is on the stem...

Then of course look for scoring (deep scoring),  not just little black lines that you cannot feel with your fingernail... slosh the psiton around in the cylinder from side to side at a few diffrent spots, look to see if you can see a worn trend...

Well, I have pissed in your ear long enough..

Good luck,

Friiy

Thanks a lot guys, I think I'll invest in a head gasket first, just so I can get a good look around. Then I'll try the penetrating oil on the valves depending how they look.
Friiy, your model number descriptions are correct. According to the docs I have, in the H series (horizontal), HH means cast iron cylinder. The one I'm looking at now is an HM100, so aluminum cylinder.
Maybe I should start a new thread & post some pics as I go along & share my discoveries with the other rookies.

Cheers

Another thing to check...

Check your headgasket, 

  If you pull the engine  over with the pull starter and you hear a chirpping noise ,  it could mean the head gasket is blown or the head needs to be retorqued....     ( mose likely the three bolts around the exaust valve loosen over time. 

Also, another way to check it is to squirt WD40 ( not a lot,  just a little to mointen things up ).. in the cylinder around the head area, put the plug back  in and try to pull start the motor..  the motor will smoke of course, so don't breath it in..  What you are checking for is bubbles around the head gasket where the wd-40 is squeezing out (Very small bubbles)

But listen for the chirp (do this without  Wd40 in the motor) , as you pull it over with the plug in and the engine set to off....

Also, don't forget to get a valve cover gasket when you get the head gasket....

Good Luck,

Friiy