M20 governor gear

[Wijeeper]

First post after a lot of reading and research. This site is a wealth of information!

I am planning to start a rebuild of an m20 that I believe broke the governor gear and subsequently snapped a rod. 

I have yet to tear it down beyond head removal, but starting to collect the parts I need led me to a governor question. Can the steel governor from earlier single cylinder Kohlers be used in place of the plastic gear, or is it recommended to simply install a new plastic gear?

Thanks

[BLT]

 BrettW might be able to give you some insight

 

[PhanDad]

Yeah, where is that @Brettw guy when you need him?

 

[Brettw]

I would purchase a new gear.  They are available on e-bay.  Kohler made both steel and plastic.  Not sure which is better or recommended.  Right now both are advertised on e-bay.  I have only come across the plastic gear in the engines I have torn down.

[RAC]

The "early" Kohler motors K341 etc allways had plastic gears. Torn apart boat load of them, never seen a metal gear. Have never seen a plastic one break. Rod broken? Probably a which came first chicken or egg type of thing. Stock rods will take lots of rev's. Rod breaks usually a lube issue.

[Brettw]

The gears on the KT's and Magnums have been know to grenade.  And the weights on the gears are the death of the engine when they are flying around inside with runaway  RPM's    Craziest I ever had was a non running M20 in a Sunstar, no compression on either side.  Figure both sides grenaded.  Opened it up to find that the cam gear had sheared about 6 teeth creating a dead spot and therefor non moving valves semi open.  No other damage.  (I did put a new governor gear in while I had it open though)

[Wijeeper]

Thank you all for the input. I assumed that the new plastic gear would be the way to go, but if the steel gear happened to fit and would eliminate a possible source of future issues it was worth checking.

Unfortunately I only ran the tractor for a few hours since I bought it, so i can't speak to the history on the engine. I started it one day and the RPM immediately maxed with an unpleasant bang from inside the engine. After a quick compression check revealing 100+ on one side and 0 on the other, I popped off the head and saw no movement of the piston when moving the crank. 

Fingers crossed that there is not too much other damage once I get it opened up.

[Brettw]

If you were fortunate enough not to put a hole in the block, that's the biggest issue.  The rest of the parts are available, and the crank will hopefully be good also as it sounds like the failure was from over-revving, not low oil.  Hopefully the governor and rod parts did not affect the camshaft, although you can usually find those used.  While apart I would hone it and put in a set of rings too.  Be good to go for a long time.

 

Edited January 18, 2019 by Brettw

[Wijeeper]

Thanks and that is my hope as well! I will be doing the rings and gaskets/seals while it is apart. Is the ball hone or three stone hone better for this type of application? Or just personal preference? I dont have either so just wanted to invest in the one that works the best....for the Magnum anyway. It seems like the service manual showed a stone hone, but I'm not sure if the ball hones were around when it was printed.

[MrSteele]

Hones. Either are good, and yes, it is a personal preference. I use a 3 shoe hone because "I always have" and I own one, do not have to buy anything. What you have to watch with either hone, though, is that you do not use it for a boring machine and cut too much. Adjust the hone for slight pressure on the shoes. Glaze breaking, what you are doing, usually only takes one trip into the bore, then back out, and at a fairly low speed on your drill. The ball hones I have used or seen used, take a lot of knowledge out of using the hone and are more forgiving., but can be over used as well as the 3 shoe.

[RAC]

Hone? Depends. Ball hone & spring loaded stone hones are really only good for de-glazing when going back to the same size bore. So basically no material removal and just restoring a cross-hatch for new rings to seat in. Oversize honing? Only use an adjustable rigid hone & even then be careful, easy to get out-of-round and taper in the bore. Neither of which you want.

Or now that I typed this at the same time - yeah what he said above!

Edited January 18, 2019 by RAC

[MikeES]

I have a stone hone so that is what I use.  My local small engine/Simplicity dealer uses a "brush hone" while flooding the cylinder in the parts washer fluid.  I had him do a couple of cylinders for me on a M20...looked good and the rings seated OK.

[Wijeeper]

Thank you for the information. Once I get it apart and confirm the cylinders are good shape to reuse, I will probably invest in the correct size ball hone as I have a 20 gth that will likely need rings in the future as well.

Are the kohler gasket sets and rings preferred for these engines or do the cheaper non-oem parts work just as well? Thanks again

[Brettw]

I have had good luck with aftermarket.  OEM is not always available, and especially difficult sometimes if oversized.

[MikeES]

I agree with Brett, I have used the much cheaper aftermarket, with no issues.  Bought on e-bay.  The complete sets will come with more than you  need, because they work on both the KT and Magnum engines.    The Magnum uses silicone for much of the gasketing (block, cylinders, closure plate) while the KT uses gaskets.  Make sure you get a gasket set that comes with the all the seals, and head gaskets, some are even packaged with new rings.

[puttputt]

I overhauled a magnum 20 two summers ago. I bought it with a broken rod. I put in a new plastic gear and aftermarket rings and seal package as well as a new Chinese carb. I had to grind just the one rod journal which was good as I could only find one rod at the time. I was lucky in that it didn't put a hole through the case. I honed the cylinders and ground the valves as well. I had to replace one tappet that got smacked by the rod. The engine seems to run fine so far with the work that was done and the aftermarket parts I used.

[Bill725]

I am not sure this is applicable in this case, but, different surface finishes are required depending on what kind of ring set you are using, i.e. cast iron, chrome or moly.

[Wijeeper]

Thank you all for the input! Good to hear on the aftermarket gaskets and rings. I hope to get it apart in the next couple weeks and start the rebuild. 

I am really looking forward to getting my snow blade/blower tractor back!