This was quoted to me when I was rebuilding my engine, and I found some pictures of it. You will need to pull the crank to get the top balance gear out.
"Don't (re)install the balance gears in an engine if it's going to turn above 4,000 rpm! (The factory maximum rpms for virtually all small gas engines, including all of Kohler engines is 3,600.)
The high rpms could cause them to break and destroy the engine! So when building an engine that's going to turn above 4,000 rpm, these gears (and spacers) MUST be permanently removed! Remember - "An ounce of prevention is worth a pound of cure."
It's okay to leave the stub shafts in the block. Or if you want, drive out the balance gear pins from the block (from the PTO end), cut 1/4" NPT threads and install a couple of 1/4" NPT Allen pipe plugs from outside the block. Be sure to use silicone sealer too, to prevent an oil leak. Or, the holes can be welded up solid.
And if a stock OEM-type piston assembly and connecting rod is going to be (re)used, there's no need to re-balance the crankshaft/piston/rod assembly if these gears are removed.
If you want, leave the balance gears out. Actually, they're more trouble reinstalling and align with the crankshaft than they're worth. You won't notice that much difference in the vibration of the engine, either. It won't damage anything and it won't hurt anything. The engine will operate just fine without them. By the way - I've seen balance gears in the 10hp, 12hp, 14hp and 16hp engines, but not every one of them have balance gears.
I've even seen some 16hp Kohler Magnum engines have three balance gears! Anyway, it seems that Kohler was selective in which engines they put them in. Perhaps they only put them in engines that was installed in a "luxury-type" of garden tractor to help reduce operator discomfort. And every balance gear I've ever seen appear to be exactly the same weight and design.
For most single cylinder Kohler engines, balance gears isn't really necessary.
Leaving them out shouldn't have a noticeable effect on engine vibrations, but they do help to reduce engine vibrations somewhat. So if you choose to reinstall or leave them in an engine that will never turn more than 4,000 rpms (this is the maximum rpms for pulling in stock classes or doing ordinary yard work), make sure that the bearings in the [balance] gears and the stub shafts that they spin on are in good condition. If the bearings are worn and if the balance gears wobble, they'll wear the crankshaft gear teeth and they could break, possibly destroying the engine. By the way - you can get the balance gears alignment tool (timing gage) from your local Kohler engine dealer. The part number is 10355 or Y-357. It's much easier to use this tool when aligning the balance gears in time with the crankshaft. See the drawing to the right for correct identification of this tool.
Once, just for curiosity, after I've rebuilt a 12hp (K301) Kohler engine, I've ran the engine with the balance gears installed. Then we took them out to see if the engine would vibrate more. (It wasn't a lot of work to remove the gears. WE just removed the oil pan, snap rings, washers and spacers, rotated the crankshaft a certain way, and then lifted the gears right out.) Anyway, we found that without the balance gears, the engine vibrated EXACTLY the same as when the gears were installed! Makes ya wonder why Kohler installs them in the first place. ????
The balance gears in a 12hp Kohler engine can be removed without removing the crankshaft. What's needed is a heavy duty snap ring pliers with 90º tips to remove the snap rings. Be sure to remove the spacers (if equipped) and shims from the shafts, too. The counterweights on the 12hp crankshaft are machined off, allowing room to remove the balance gears. But on a 14 and 16hp engine, the counterweights may be in the way. If it is, try driving the pins from the PTO end of the block instead and then plug the holes from the outside with a couple of 1/2" cup-shaped expansion plugs.