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Cub engine queston?

Post in 'The Gear' started by smokinj, Jul 22, 2013.

  1. Jags

    Jags Moderate Moderator Staff Member

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    Don't use any lapping compound unless you are gonna tear down that engine. Pretty tough to insure that some doesn't go where it shouldn't. Lapping is usually done with a tool (power tool). There is an inexpensive method that looks like a dart that kids stick to windows, and it is run with a drill and lapping compound.

    If the carbon on the valve seats is not evenly distributed it tells be that there is a hot spot. Just a matter of time before she burns through if it is not addressed.

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  2. Jags

    Jags Moderate Moderator Staff Member

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    I'm in IT - what can I say?


    Sent from my iCoke using fizztalk 2.
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  3. Joful

    Joful Minister of Fire

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    Easy enough to remove these flat head valves for cleaning. Pull breather, pair of keepers, valve slides out. Not really a big deal, and that's as much tear-down is recommended in the shop manual for doing a valve job on this engine.

    ??? Not on a Cub engine!

    Yep... this is all I've ever seen anyone use on these. However, I've never seen one run on a drill. Usually spun between the palms like kids pretending to start a fire with a stick.


    You nailed it. If there's crap on the seat, it's usually time to re-cut and lap in a new pair of valves.
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  4. smokinj

    smokinj Minister of Fire

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    Haha.....Its consistent and there not much there. Just don't want it falling into the engine. Kerosene rag may have loosen it up enough I can wipe it off. Head gasket will not be here until Friday afternoon so I can really tweak it out. Should even have time to at-least polish the head to.
    Guy said it was re-built 4 years ago and everything I am seeing says he is right.
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  5. Jags

    Jags Moderate Moderator Staff Member

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    I watched a machine shop lap the valves on a short block I did years ago. Yes, it was a large machine. I also have the suction cup tool and use it on a drill. Works great. (mine only has one suction cup, not the double ended kind.)
  6. smokinj

    smokinj Minister of Fire

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  7. smokinj

    smokinj Minister of Fire

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    That is correct other than most would use the hand tool for the kohler flat head. I don't think its going to take much other than cleaned.
  8. Jags

    Jags Moderate Moderator Staff Member

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    That is good news.

    I actually pulled the first part that you quoted, Jay. I think I misunderstood Joful.
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  9. Joful

    Joful Minister of Fire

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    Grinding/cutting valve seats is usually a machine operation, while lapping valves to those seats is generally done by hand on garden tractors.

    To respond to your first sentence (deleted), you actually can buy new valve seats for the K301, which are pressed into the block. If your block already has replaceable seats, you can pull them and press in the new ones. On a stock K301, you first have to machine the rebate to accept the replacement seats.
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  10. Jags

    Jags Moderate Moderator Staff Member

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    Yep - that is what they did on the short block I had work done on. Pretty interesting operation. Since they already had the mill setup for the proper seat position, they just hooked up the lapping tool and did the job right there.
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  11. smokinj

    smokinj Minister of Fire

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    I hopping it not be needed. Here is a line from Brian's Cub page see what you all make of it?

    "FYI - In most cases, worn valve guides don't necessarily need to be replaced. They can be repaired with a thin-wall bronze liner, like the ones installed in automotive cylinder heads. Also, a bronze liner will last longer than a cast iron guide because bronze retains more oil for better lubrication for the valve stem."
  12. Jags

    Jags Moderate Moderator Staff Member

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    I would imagine to use a liner of that type you would need to ream the guides to a specific spec. Dunno, never used the liner stuff.
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  13. smokinj

    smokinj Minister of Fire

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    That makes since now. Thanks
  14. Joful

    Joful Minister of Fire

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    Those guides are too easy to replace to bother re-lining. You basically tap them with a thread using a hand tap, thead a piece of all-thread into them, and use a nut with washer to draw them out. Then you hammer the new ones in (can do by hand, but I prefer to use a $10 drive tool for the pneumatic hammer) to a specified depth. This is the only tricky part, as you don't want to overshoot that depth (easy to do). Then you hand ream them (I can loan you the reamer, which was a little 'spensive), and drop your new valves in. Easy peasy.

    Actually, I can loan you the drive tool, if I'm already sending you the reamer. Otherwise, buying your own drive tool is probably about the same as the cost shipping mine.
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  15. smokinj

    smokinj Minister of Fire

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    I will get a much more detailed look tonight. I learned a lot and if it needs it I will take you up on that.
  16. MasterMech

    MasterMech Guest

    I highly doubt a recently rebuilt K series engine has any significant wear on the valve guides. If the guides and the valve stem are tight, there is no reason you can't lap the valves if you want. Remove the keepers and springs, which you probably already have done to check for valve guide wear, and clean things up the best you can. The seats can be re-cut by hand with a special set of tools (which can also be used in a drill press or Bridgeport) but try to borrow them as they can be a bit pricey if this is a hobby job. In your case, I'm betting the seats are clean with no pitting anyways so recutting them will not be necessary. Lap the vales in using fine compound and either the suction cup type to or a lapping tool that kind of resembles an egg beater. Do not do so with a drill. A light touch is necessary and reversing direction as well. Grind by rotating in one direction and then rotating a bit farther in the other, keeping the valve in light contact with the seat. Continue until you see a light grey band appear all the way around the valve face that's a consistent width. Use the compound sparingly and when you are done, make sure you get it all off. DO NOT ATTEMPT TO FLUSH THE COMPOUND OUT WITH A SOLVENT. You are likely to rinse grit into places you definitely do not want it.
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  17. smokinj

    smokinj Minister of Fire

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    Yea its is just a hobby for sure and full time wood hauler. I am into this tractor so far under 600.00. Right is right and cheap is better. I still got paint and tires to go. ;) But I will get a better look at it tonight.
  18. smokinj

    smokinj Minister of Fire

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    Looking closely and wipe it down again it looks good real good. I THINK the rest will come off just by wiping it with paper towel and kerosene
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  19. Jags

    Jags Moderate Moderator Staff Member

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    Jeesh - no love for the drill. A reversible with an accurate trigger and it is done in no time.>>
  20. smokinj

    smokinj Minister of Fire

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    On these kohler doing it by hand takes just a few seconds to a couple mins. That it. Drill or press would be to much of a chance of over kill quick.
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  21. Jags

    Jags Moderate Moderator Staff Member

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    I guess I will have to go tell the engines that I have done this to, to quit running right.;lol
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  22. smokinj

    smokinj Minister of Fire

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    Well my engine dose not need it at all......After cleaning it up again last night it looks brand new. Have you done a flat head kohler before?
  23. Jags

    Jags Moderate Moderator Staff Member

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    At least 4 of them. I currently run two - my yard hauler and my small mower (both 12hp). I have freshened up both at some point. (1976 and 1977 with mega run hours).
    alkfirewood4sm.jpg
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  24. smokinj

    smokinj Minister of Fire

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    I would not quite then. Nothing quite like the Sound of a 301k. :) Is that an Allis?
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  25. Jags

    Jags Moderate Moderator Staff Member

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    I have also done a 10hp that was on a high wheel case and a 16hp that currently mows my mothers yard (same AC tractor as mine, just the 16hp version and a bit newer).
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