Magnum 12 help needed

[wrightorchid 261]

I think my motor has died.  It recently started running rough, and now it is at the point where it will bog down, and almost stall under load, or going up hill.  I replace the air filter, and plug, which was full of carbon.  I ran it some more, and it fouled again.  When idling, it seems to miss , or pop.  I don't think this is good.  I don't know how to rebuild it, and not sure if anybody in the area does.  I am starting to look now.  Like auto shops these days, they just replace parts and don't rebuild.  It has run for a long time with a hole in the muffler, so I am wondering if the exhaust valves are toast.  

 

One of the local shops said they would look at, at $72/hr labor, plus parts.

 

Any suggestions?

 

Thanks,

Mike

Tallahassee Florida

Edited August 29, 2014 by wrightorchid

[Lane Ranger 10,495]

I would suggest draining your gas tank first of all the fuel.    Put new clean gas and buy some Seafoam for removing carbon and cleaning the motor and carb , etc.  You can also use a tad bit in oil  and change it too while at it.    You can have build up, water in gas from Ethanol, etc.    See if this does not improve performance first before going the route of taking to a shop to work on !  You may be surprised with the results. 

Edited August 30, 2014 by Lane Ranger

[can whlvr 991]

if what lane said doesn't work id pull the head,then look at valves and decarbon,clean head,got nothing to loose

[Fordiesel69 214]

Please make a video, and post a link to it here.  When can all listen to it, and tell you if it is a mechanical problem internally to the engine, or if it is something simple like a fuel or spark problem.

 

We have a lot of awesome folks here that can basically walk you thru it so you do not have to get ripped off at a shop.  If you can operate a screwdriver, you can fix these engines.

[ranger 1,639]

Hi from UK     Does your engine blue smoke when running,burning oil ? Do you have the Walbro carb with the non adjustable main jet ? If you've been running under load for a while with a hole n the muffler, it will have run on a weak mixture and could have burnt an exhaust valve or damaged the piston.Hopefully you will find a leaking exhaust valve which just requires re-seating and adjusting,   Have you checked the valve clearances ? I had a similar problem with a C121 with a 'tight'. exhaust valve, it ran fine until it warmed up then would not idle and popped and banged. Your plug fouling could be caused by worn/damaged piston rings or valve guides.There are manuals available for free which will help you to rebuild your engine for probably the cost of a shop spending 2-3 hours 'looking' at it and quoting for the repair! If you can change a plug etc, with a half decent toolkit and a manual,   You shouldn't have too much trouble,and as Fordiesel69 has said, there is a lot of help available here. :thumbs:

[Helenstractor 0]

My 12 hp Kohler K301AS froze up. I pulled the head now I have to figure the rest out! That's why I just found this forum and registered. If I find a person who is interested in my C121 (with plow attachments, I am the original owner with full documentations) then I may sell it. If not I'm planning on rebuilding the engine.

If anyone reads this.....I need help figuring out everything about this tractor, the forum and what to do!!! Thanks in advance for any suggestions.

[wrightorchid 261]

I hope to make a recording of it this weekend.  I have been way too busy to start taking it apart.

Aside from a spring compressor, and a torque wrench, any other specialized tools that are needed?  

[MalMac 1,328]

You will need to down load the Kohler manual. You can get it off of the Kohler site and here on Red Square. You will all so need a gear puller. Look at the Manual and it will show what you need.

[nhunt308 143]

Sounds like the same problem I had with my magnum 12 and mice had chewed the insulation off of the spark plug wire back under the metal guard and causing it to arc. I would check for something like that

first I may be wrong in your case but worth a look.

[PaulC 341]

Check the muffler itself!!! I had a weird issue out of no where earlier this year with my tractor.

 

I spent a lot of hrs this winter giving my horse a new paintjob and fixing up anything else I found along the way. The motor runs great with no smoke. First time mowing the lawn with it this year I just got finished and pulled up behind the house brought it down to idle and it started running terrible!! I feared the worse and didn't want to believe it. I ended up taking the carb off and cleaning it 3 or 4 different times and even swapped it with the carb from my other horse. Got to talking with my younger brother about the symptoms and he said it sounded just like a car he had to where the exhaust cats got plugged up. I didn't think that was the problem but he convinced me to swap mufflers just because it was so easy. To my surprise it fired right up and was back to normal!!!

 

With you saying your muffler is rusty to the point of a hole makes me think you could have the same issue I did. The inlet pipe that mounts to the block is short baffle with a series of holes in it and its capped on the end. Mine rusted to the point the material between the holes finally let go and got lodged in just the right way to where the end cap of that tube plugged the outlet port.

 

I spent a bunch of hours trying to figure it out and I could get it to start and run kind of ok but as soon as id turn the pto on it would bog right down like you are describing. I think it was essentially trying to intake and exhaust through the carb. itll be pretty loud but I say take the muffler right off and try to run it you will see a night and day difference right away if that's your problem.

 

Those mufflers are really pricey but I was able to cut mine apart remake a new inlet and weld it all back together. Keep us posted on what you figure out and if you need any more info on anything I said let me know!!

[Fordiesel69 214]

I hope to make a recording of it this weekend.  I have been way too busy to start taking it apart.

Aside from a spring compressor, and a torque wrench, any other specialized tools that are needed?  

 

How are you coming along with the video.  Your problem sound simple, and fuel related.  You probably do not need to take the engine apart.  Oil burning and knocking would indicate the need to take engine apart.

[wrightorchid 261]

It's been a while, but I had a little bit of time today.  I've had more of share of unexpected problems and expenses to last a while, I hope.

 

Anyway, I have pulled the head, and it was nasty.  It is pretty much clean now.  The old gasket was pretty well shot, and the head bolts were not very tight.  I have a new Kohler head gasket now.

 

The cylinder bore looks pretty worn/  no hash marks, and very shiny.  There are a couple of vertical marks, but barely.

 

The valve do not appear to be burnt..   The exhaust side of the head does appear to be a bit darker than the rest.

 

The main issue was low power immediately under load.  The plug would also foul with lots of soot.  It progressively got worse over time until not usable.

 

I took lots of pictures, and will be posting shortly

Edited February 22, 2015 by wrightorchid

[can whlvr 991]

I would think that if your head gasket is shot than that is probally the main prob along with loose head bolts,these kohlers will run along time with lower compression as long as you keep the oil full,put a new head gasket on,and check the head for flatness on a piece of glass and a feeler gauge,you can hone the head with a flat surface and sand paper,working to a fine grit install the gasket and head,torque her down and see what you end up with

[wrightorchid 261]

^{This sounds simple enough.  I don't see any real signs of warpage.  In the past, it was pretty easy to start.}

Edited February 22, 2015 by wrightorchid

[Fordiesel69 214]

If we can hear it when it is acting up, we can be a lot more helpful.

[wrightorchid 261]

I'l put it back together an make a video. It was making a little bit of a popping sound,but not like a backfire. Might be a few days till I have more time.

[wrightorchid 261]

After cleaning the head and valves, replacing a fuel hose to the carb, spark plug, air filter, and muffler it is back in action!!         I think a rebuild would be good in the future, but good for now.  The grass is growing, and always something to haul on the 2 acres.

 

Thanks to all for your eagerness to help, and suggestions.  

[can whlvr 991]

that's good news,its nice when its a simple fix