Kohler mounting threads stripped

[SuzukiT350man]

I have to clarify that this thread IS NOT about a Cub cadet, but can be used as a resource for others with the same problem.

I recently got a early 90’s John Deere STX38 with low hours back running, and everything works as it should. Other than the engine mount bolt holes are stripped. It has a Kohler Command 12.5 on it, which was used on some MTD cub cadets I believe. All of the holes are stripped and the bolts fell out long ago, and it’s only held on by 1 bolt where the Electric PTO ground is. There’s always gonna be a right answer or a wrong but acceptable answer.

I thought about taking the motor off to drill and tap a bigger hole and replace the bolts, but once you start there’s no going back (especially since it’s aluminum). This engine in particular has very little use on it, but the previous owner definitely didn’t know too much about aluminum engines.

I would use a helicoil but it won’t be strong enough to handle that vibration, and I could try using some steel stick and drill/tap it but it could go south in an instant. Anybody got any tricks up their sleeve to throw at me?

[Oak]

Got any pics?

TIG weld them and re-drill.

[finsruskw]

Aluminum deep sump pan??
If so, pitch it and get a cast iron replacement.

[Ambush]

Helicoil will handle any load or vibration the original hole would and more. Some manufacturers of expensive machinery that utilize aluminum casting, Helicoil from the factory. Volvo Penta marine being one.

I've used them many times in repairing hydraulic pumps and motors. They are not a stop gap, better-than-repair when installed properly. Problems occur when the installation is sub standard.

You can counter bore the hole with a 45 degree burr, (or hog it out with a bullnose burr and die grinder) then tig weld it in, but you better be able to relocate your holes accurately. And there is a good chance the threads in the weld will gall as the weld material is likely softer than the casting.

Install the Helicoil as per instructions. Use a drill press for oversizing the holes and for starting the tap. Cut the coil off with a zip blade or Dremel flush at the surface. If the motor has been bouncing around for a while, then it's also a good idea to put the pan on the mill and level all the pads.

If you don't have the equipment to do the job properly, you can't expect good results. In that case, you should definitely just buy a good component.

[finsruskw]

The mounting bosses will likely be worn un-evenly leading to a cracked pan when torqued down.
Best to have them milled even and flat again before mounting before the heli-coil repair. The drilling and tapping for that repair can be easily done at the same time whilst mounted on the mill table.

[darkminion_17]

Originally Posted by finsruskw

Aluminum deep sump pan??
If so, pitch it and get a cast iron replacement.

There is no oil pan on a engine like that. Helicoil is the way to go.

[CubDieselFan]

We use these at work.

https://www.clarendonsf.com/products...ensert-inserts

[Cannon51]

I had to put HeliCoils in a CV15. It had 8mm-1.25 bolts that held the engine. 3 were striped but I put HeliCoils in all four. With the flywheel cover on it set level on the drill press table for drilling. I bought the kit and have enough for another engine. Check the threads, I don't think they all use the same bolt.
Cannon

[cubby102]

Originally Posted by SuzukiT350man

I have to clarify that this thread IS NOT about a Cub cadet, but can be used as a resource for others with the same problem.

I recently got a early 90’s John Deere STX38 with low hours back running, and everything works as it should. Other than the engine mount bolt holes are stripped. It has a Kohler Command 12.5 on it, which was used on some MTD cub cadets I believe. All of the holes are stripped and the bolts fell out long ago, and it’s only held on by 1 bolt where the Electric PTO ground is. There’s always gonna be a right answer or a wrong but acceptable answer.

I thought about taking the motor off to drill and tap a bigger hole and replace the bolts, but once you start there’s no going back (especially since it’s aluminum). This engine in particular has very little use on it, but the previous owner definitely didn’t know too much about aluminum engines.

I would use a helicoil but it won’t be strong enough to handle that vibration, and I could try using some steel stick and drill/tap it but it could go south in an instant. Anybody got any tricks up their sleeve to throw at me?

heli coil works fine, currently running them in two cubs for about 4 years, and in my dads zero turn deere which gets ran 2 days a week for a minimum of a hour and a half at a time, zero issues. (i do use red loctite when installing them)