Craftsman 12 HP Lawn Tractor (Tecumseh)

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  #1  
Old 05-14-08, 03:03 PM
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Craftsman 12 HP Lawn Tractor (Tecumseh)

Alright, looking for some advice here. I received this from a neighbor about 5 years ago. It was in decent shape, but has sat in the shed for a while. Deciding I could finally use it, I put a battery in it, changed the oil, and out gas in it. It started right up and ran at full throttle. Hmm, something wrong with the carb. I also noticed that gas was coming out from the carb. So I figure I'll take the carb out to replace the float and rebuild it. The throttle pate is missing! Well that explains the full throttle. So I take off the intake manifold and lo and behold there is nothing in it. This is an overhead cam engine vintage ~1988. Craftsman 143.396092 if anyone cares. So looking at the intake valve, it appears that there is no way that the throttle plate could have been sucked into the engine without seriously being reduced in size (agree?). The screws would be a different story. The owner of this is no longer with us so I can't ask him. So my gut says I need to take the head off to see if anything is hiding in there, but I still can not believe that the throttle plate made it into the engine. This does not appear to be a real easy task. A few new parts should make the carb as good as new. So should I start it and see what happens or take the head off? It ran for about 30 seconds with the throttle wide open, so if parts got sucked in the damage is probably already done. It ceratinly sounded fine when it ran.

Thanks,
Ken
 
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  #2  
Old 05-14-08, 07:08 PM
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Originally Posted by kflorence View Post
should I start it and see what happens or take the head off?

Ken,

I'm here to help others repair machines, I'm going to let you make that call.....

Myself, I just couldn't take the chance working in a shop as I do.

Good Luck
 
  #3  
Old 05-15-08, 12:12 AM
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I'm thinking along the same lines. I have a couple of Kohlers in the shop that lost the throttle plate as well. Both of them have throttle plate screws embedded in the pistons. I think I did find the plate in one of the engines crammed in the intake, but I don't think I ever found the throttle plate on the other. Who knows what happened to it. Anyway, the screws are bound to cause problems. I can see where the screws got mashed in the piston, came back loose, beat around some more, got stuck again, etc... until the top of the piston and the head looked like hamburger.
 
  #4  
Old 05-15-08, 07:23 AM
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Yea, my thoughts are a quick look is a good idea. That way I can also see how things look in general. I do not have the service manual yet for this engine. How hard is it to pull the head to take a quick look? Also, since I have worked on bigger engines, but not smaller ones, when the head is off, is it wise to get it machined? Do shops that do car engines do this or do I have to take it to a mower shop to have it done? Torque specs and all that should be in the service manual when I get it. From looking around, it seems to me that I'll need a special tool to be able to remove the head. This is an overhead cam.

Thanks for all the advice, I do appreciate it!

Ken
 
  #5  
Old 05-15-08, 07:29 AM
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Actually I meant to say overhead valve below!!!!!
 
  #6  
Old 05-15-08, 09:07 AM
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Ken,

It depends on the condition of the head if it needs any work performed.

I don't know of any special tool required to remove this head, Here is a link to a Tecumseh service manual that will have destructions on head removal.

http://toprake.com/index.php?module=..._Document_id=9


Good Luck
 
  #7  
Old 05-15-08, 09:52 AM
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Thanks for the link and the advice. Looks like it should be pretty simple to me to get it off and thus for the cost of the gasket it would be worthwhile to see if any surprises are lurking inside. Will probably pull it this Saturday. I'll let you know if I find any "treasures" hiding inside!

Ken
 
  #8  
Old 05-15-08, 07:45 PM
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Good deal Ken......
 
  #9  
Old 05-29-08, 07:55 AM
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I certainly had trouble getting back here! Well, it turns out that the screws and throttle plate were in the engine. Both were embedded in the head. Amazingly enough, the valves and cylinder are fine I have cleaned up the piston top and head and was ready to put it back together over the weekend. However, the engine had been apart and someone had stripped one of the head bolts. It had been helicoiled and the helicoil pulled out during the torque process. Now I noticed that the holes are much deeper then the bolts and there is good "meat" in that screw hole. So it appears to me that I could put in a slightly longer bolt then what was in there originally (it looks like I got a good 1/2"). So is that a reasonable way to work around this situation?

Thanks again,
Ken
 
  #10  
Old 05-29-08, 10:11 PM
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Worth a try... 1/2" isn't much area though.
 
  #11  
Old 06-03-08, 11:14 AM
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Well it held. Torqued down fine. Should be ready to try and start it this coming weekend. I just need to figure out how to tighten the valve adjusting lock nuts without moving the adjuster nut. Its to darn small to get a wrench down there to hold the adjusting nut. Any advice as to how to hold that nut from turning? My manual says both intake and exhaust should be .004 in clearance.

Ken
 
  #12  
Old 06-04-08, 12:26 AM
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I don't recall ever using anything other than a regular wrench.
 
  #13  
Old 06-04-08, 03:19 PM
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The nuts almost touch the sides of the rockers. You must have some mighty small wrenches (thin)!!! I'll figure something out....
 
  #14  
Old 06-04-08, 11:18 PM
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Just angle the wrench in perpendicular to the rocker. You can get enough bite to hole it that way.
 
  #15  
Old 06-07-08, 04:39 PM
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Well got it mostly back together today. I just used a box wrench to hold the bolt. It turns over by hand so the compression release seems to be holding OK. However, it does not want to run. The only way I got any sign of firing was using starting fluid. In the process the starter switch broke, so that may be some of the problem. It has a new carburetor on it. I started with the main jet screw (bottom of carb) turned out about 1.5 turns. Is that about correct? Anything else to look for? If the valves are not spot on (although I think they are) can that cause problems with this engine? It was running when I opened it up, so it should run now!!!

Ken
 
  #16  
Old 06-08-08, 08:50 PM
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What does it do? Pop and backfire?
 
  #17  
Old 06-09-08, 07:48 AM
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No it was jut turning over and not firing at all. Just felt like you were turning the engine over without the spark plug connected. With the starting fluid, it did start and run for a couple seconds and then died. My starter switch then busted. So I have a replacement coming for that and will try again. I hate using starting fluid cause it runs so hot, but it at least tells me I have ignition.
 
  #18  
Old 06-09-08, 09:44 PM
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If it runs on starter fluid, then it's not getting fuel. That indicates a carb problem.
 
  #19  
Old 06-10-08, 08:08 AM
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Yes, that would be my thought, but it is a brand new carb (yes I guess it could be bad). That is why I was asking about initial mixture screw settings (although I'd still expect a pop or something even if these were set wrong). Once I get the starter switch back in we'll see where we go.
 
  #20  
Old 06-10-08, 08:50 PM
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If it has a fuel shutoff solenoid on the carb, that could be the problem, especially if the ignition switch is faulty and not sending power to it.
 
  #21  
Old 06-11-08, 11:26 AM
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I do not believe it does. Do not remember disconnecting any wires from the old one. The carb bowl does have gasoline in it. However, with the switch in a breaking mode who knows wat can not happen right. I'm keeping my fingers crossed it will act differently with the new switch. If not, I'll be back with the symptoms!!

Ken
 
  #22  
Old 06-15-08, 09:11 AM
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Alright, well with the new switch it started. It appears that the governor settings are wrong. It wants to run wide open. I believe that the linkage to the throttle is incorrect (I put it back on the way it was). Anyone familiar enough with this engine to tell me how it gets set up? It would appear to me that the linkage to the throttle plate from the governor, should go on the hole opposite of where it was. That would mean that when the governor is pushed counterclockwise that the throttle is wide open. The governor spring looks really new and it is pretty hefty, so I wonder if that is a wrong part also.
 
  #23  
Old 06-16-08, 09:14 PM
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Hard to tell about the spring, except there shouldn't be anything "hefty" about it.

Generally you can tell which holes were originally used to make the linkage connection by close inspection of the holes themselves. Usually the ones used will have wear marks and be a little less perfect of a hole than the ones that aren't used.
 
  #24  
Old 06-17-08, 08:42 AM
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The spring is pretty strong and looks new. So if I understand the way the governor works, the spring will hold the throttle in a wide open position until the governor pulls against it (as RPMS increase, the governor weights push out and the governor lever pulls against the spring and will close the throttle down some). The way the linkage was hooked up, it was holding the throttle full closed and as engine speed increased it would push the throttle more and more opened - thus the running wide opened. Putting the linkage on the other hole in the throttle would do the opposite (and I believe correct) action. However, the spring requires quite a bit of force to pull against and could be holding the throttle more opened then it should be.
 
  #25  
Old 06-17-08, 09:54 AM
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I have never seen a governor spring that I would call hefty as in it needing any significant force to stretch it. It's not a application that needs a lot of ummph. What the spring should do is open the throttle a little as rpms drop due to increased load (like hitting a patch of high grass over the septic tank), to increase power as needed. I suspect you have an incorrect spring installed by a previous backyard "engineer".
 
  #26  
Old 06-17-08, 11:16 AM
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Well there is no doubt that the previous owner had worked on this! The carb was hooked up wrong as long as governor function is as I describe below. I really suspect as you do the spring is not the correct one. If I grab one end in one hand and the other in the other, I can open it up, but it requires a lot of pulling power. I am betting that it was replaced with one from a hardware store parts box! The spring is about the size and thickness of my little finger (a little shorter). The governor springs that I have seen on 6 - 8 HP engines have been much "weaker" then this one, that's for sure. The tecumseh part number for the spring is 35521. Guess I need to find one.
 
  #27  
Old 06-23-08, 08:40 AM
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Well, I put a new governor spring on it, hooked up the governor/carb as I thought it should be (as opposed to how it was hooked up when I took it apart), then adjusted the governor mechanism as per the service manual and it started right up. I adjusted the new carb and it is running quite smooth. It has a pop (like a miss) every 10 or 15 seconds (many small engines tend to that from my experience). So for a close to 20 year engine I guess I can not complain. Put the mower deck on it and mowed my yard (the miss seems to disappear when the blades are running). It climbs hills without changing speed even when mowing. Guess I just got myself a cheap rider!!! Thanks for all the help....
 
  #28  
Old 06-23-08, 08:26 PM
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That's good to hear. Sounds like you've got it running quite well....Thanks for the update!
 
  #29  
Old 06-23-08, 08:34 PM
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Originally Posted by 31YTech View Post
Ken,

It depends on the condition of the head if it needs any work performed.

I don't know of any special tool required to remove this head, Here is a link to a Tecumseh service manual that will have destructions on head removal.

http://toprake.com/index.php?module=..._Document_id=9


Good Luck
hey you wouldn't happen to have a link for a briggs n stratton repair manual would ya ?? i got a 5 or 5 1/2 horse lawn tractor with a symilar problem
 
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