Need Help with Antique Tecumseh, Long

Discussion in 'Mechanic and Repair' started by MBDiagMan, Oct 9, 2012.

  1. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Posts: 852

    You're right Jim, I looked and the o/s valves are no longer available. I don't have a press. I wonder if I could drive the guides out with a drift and hammer once I warm up the head with a rosebud?

    After thinking about this, since it's making what appears to be decent compression at 110PSI dry, I'm thinking that once the head is off, if the valves and guides are seriously worn as you describe and if the bore looks good, I might just redo the head and slip it back on without doing the bottom of the motor.

    That said, you never know what you're going to find until it's apart.

    Thanks again!
     
  2. JimQ

    JimQ LawnSite Bronze Member
    Posts: 1,139

    Im sure that would work to get them out. Then maybe a piece of wood or nylon to get them back in. I would give it a shot. I went through the bottom end (bored .020" over) but that was because it was getting so sloppy, you could hear the piston slap. It had 1600+ hours on it running at 3750 RPM. It was cranked WAY up.

    Q
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  3. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Piston Slap....?????
    I should know something about that....good thing they don't knurl pistons anymore..
    They were so abrasive...they hogged out the bores...
    When checking the welder..find and check the connections on the square fullwave rectifier...wires like to melt and make it not weld so good....
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  4. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Posts: 852

    Got the head off last night & yes the valves are a pita.

    The exhaust valve/guide is loose. Rattles probably four thousandths or so. Oil had clearly been running down the exhaust valve. Intake good &tight though. Both valve faces & seats look good & are sealing well.

    The piston top was clean as a whistle & no ridge at top of bore. Miced cylinder with piston at bottom. About .006 or .007 wear across thrust dimension above lowered piston.
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  5. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Get a new set of rings.....insert the new top ring at the top ...middle..and bottom of the bore.
    Using a feeler gauge...measure the ring gap...Anything more than .020 - .025 is bad...
    while it may run..it would probably use oil....and maybe even piston slap.....
     
  6. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Posts: 852

    Thanks Slapper!

    I used to measure cylinders with the method you describe and it works quite well. Since I now have a set of inside mics, I come up with a cylinder that is very close to the limits your method indicates.

    With .006 added to bore dia X Pi, you get ALMOST .019 additional bore gap. Add that to the .0035 or so that the gap would be in a new cylinder and you are right in there at .0225 gap, which is smack dab in the middle of your limits. In the real world, a new ring squared up in the bore might be something less, since the sides of the cylinder adjacent to the piston pin are probably not worn so much.

    All that said, it would seem that it would be marginally acceptable for working out with new rings.

    At this point, considering that it's making decent compression and the oil usage is probably due to the worn exhaust valve and guide, and since the engine was actually running pretty good, I'm thinking I'll fix that and see how it does.
     
  7. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Posts: 852

    Well I've been buried with other things to do and also took awhile to get the parts. I got in the new guide and valve with a fresh valve job. Good news... it seems to run a little better and smokes a little less. Bad news.... that's not good enough.

    I ordered an overhaul kit including piston, rings, gaskets and seals for a good price, less than a gasket set and rings from other suppliers. I should get the parts next week and tackle it that weekend.

    I'll keep everyone posted.

    Doc
     
  8. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Posts: 852

    By the way guys. The OH160 manual says to ALWAYS use new rod bolt nuts. If they don't come in the kit, do I really need to get some?

    Thanks for your help.
    Doc
     
  9. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Doc...its a judgement call....use your best judgement....and make the call...
    Probably be just fine...use your torquewrench...if they torque firmly ..theyre ok..
     
  10. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Posts: 852

    Thanks slapper!

    I got my overhaul kit Saturday. I had the welder in the back of my pickup backed in the shop. The light engine work I've done so far, I just sat in the truck while working. Now that I'm going farther into it, I lifted it up and drove the truck out from under it. It's a four wheel drive, so it was a pain getting in and out of to fetch tools. Working on it while in the bed of the truck was a good plan that didn't turn out so good.

    When I set it on the floor yesterday, I pulled the plug to drain the oil. The oil came out nice and clean FINALLY. The soaking the innards in diesel fuel finally cleaned it out.

    I fell Saturday on my tailbone and I'm sore. I have a roll around chair I was planning on using to work on it while it's on the floor, but with my tailbone like it is, I might be walking around on my knees instead.

    Looks as if I'm FINALLY getting down to the meat of the project.

    I'll post progress as I go.

    Thanks for all the help.
    Doc
     

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