1997 MTD Lawn Tractor Variable Speed Pulley Issue

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  #1  
Old 08-08-14, 12:27 PM
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1997 MTD Lawn Tractor Variable Speed Pulley Issue

Model number: 13AG675G033 serial:1L096C60045. Engine is Tecumseh OHV16-204216D(H) D.OM. 63265.

Hey Cheese, you helped me big time with my last problem, so I'm hoping you can lend some more assistance.

She started up and ran great, no problems. Mowed a few strips and I stopped. Put it into reverse, lifted the blade and backed up a few feet. no problem. Put her into forward-no go...OK, no big deal, happened before when the belt for the variable speed pulley fell off. I put it back on and now she won't crank. Spins maybe 2 or 3 times and stops. There is a bit of resistance when I try and spin the engine by hand. Something is bound up and I think it my be a belt or pulley. I did not hit anything or run over anything either. The grass was a bit damp when I started, not soaking wet, by any means.
Where should I start to look?
Thanks in advance. Your advice before was spot on.
Dave
 
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  #2  
Old 08-09-14, 02:24 PM
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Update...I pulled out the spark plug and was able to spin the engine by hand a bit easier, but there is still a lot of resistance. I took off the starter, left it wired up and turned the key, the starter spun a few times then died. I took it apart and found that a wire to a brush was burned through. I repaired it and after much effort was able to put it back together. I hooked it back up and verified that it spun. With the plug out it will crank the engine. It looks correct. When the spark plug was installed, engine spins twice and stops abruptly. Battery was recently load tested and verified good. I am back to square one. Should I try a valve adjustment? Any input would be appreciated.
Dave
 
  #3  
Old 08-09-14, 07:11 PM
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I'd look at the valves, and not sure how confident I am in the starter either. How did you repair it?
 
  #4  
Old 08-09-14, 09:27 PM
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Hey! Good to hear from you Cheese!Thanks so much for the reply.
I used to do repairs on small DC motors long,long ago. I removed and wiped off the armature, wiped and inspected the 4 magnets to assure they were not cracked, I found the longest braided wire going to one of the four brushes (covered in cloth) had most likely been abraded by the spinning armature. The cloth insulation had a hole in it and the braided wire was cut/melted in two. I cleaned both ends, hit it with a small amount of flux and soldered it back together. Reused the cloth insulation and the hole in the cloth was covered with a small amount of electrical tape. Getting the brushes back in was a challenge...I pulled the springs back with some sewing thread and after I got the cap situated on the armature and housing...I snipped the thread. I heard the brushes click into place. I'd say they were only worn about 1/2 way. I applied 12 volts and she spun just fine. I mounted it back on the mower and with the plug out it looks like she is able to crank the engine fine. When plug was installed just got maybe 1 and a half revolutions then abruptly stopped.
I'm thinking the spec for both valves is .004 gap at TDC. I will give it a try in the morning. I will let you know what I find.
Dave
 
  #5  
Old 08-09-14, 10:00 PM
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Okay, sounds like you know what you're doing with the starter then . I'd go for the valve adjustments. Set them with the piston about 1/4 inch past TDC to eliminate interference from the compression release.
 
  #6  
Old 08-10-14, 03:46 AM
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Will do Cheese..1/4 inch past TDC. I will wait for daylight.
*grass is getting long!*
 
  #7  
Old 08-10-14, 03:07 PM
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Set valve lash to .004 1/4 inch past TDC...still no change, I get the engine to spin fine with the plug out, but when the the plug is installed it is sluggish. I have seen several videos online of OHV engines that have the same symptoms as mine, where people think the starter is bad, but all it needs is a valve adjustment. Maybe the starter motor is just weak or has bad windings but I don't understand since it spins the engine normally without the plug...maybe it is just because the load is considerably less? I double checked spark it is blue/white. It is getting gas.
Dave
 

Last edited by truenorthdv; 08-10-14 at 04:47 PM.
  #8  
Old 08-10-14, 06:58 PM
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Sometimes the compression release breaks on the camshaft on these. It's a really cheaply made device that commonly fails. Slowly turn the engine while watching the exhaust valve. It should bump open a hair just before TDC as you turn it.
 
  #9  
Old 08-10-14, 09:00 PM
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Could a weak started give these same results where you are unable to cycle the valves?
Dave
 
  #10  
Old 08-10-14, 09:29 PM
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A weak starter could cause the symptom, watching the rocker arms while you manually turn it will help to know if you need to focus on the starter or not. If the windings on the armature didn't look like they got too hot, the starter didn't have that burnt smell, and the bushings are not binding, it is probably okay.
 
  #11  
Old 08-11-14, 07:09 AM
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Thanks Cheese, I will look closer at the valves and check for the bump of the compression release.
I appreciate your help and patience.
Dave
 
  #12  
Old 08-11-14, 09:19 AM
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Ok...I carefully watched the rocker arms and I clearly saw the exhaust valve bump open just a hair. I advanced 1/4" past TDC and set both valves to .004. The starter just hummed even with the plug out.
I took out the starter and applied 12VDC...nada-tried to advance the armature to see if it would catch..it is dead in the water. I ordered a new starter. Should be here in a few days. I will report back on the situation. I'm just glad there was not a problem with the compression release. Thanks so much for your help, Cheese.
Dave
 
  #13  
Old 08-11-14, 09:51 AM
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Glad the compression release is working, I think the starter will fix it.
 
  #14  
Old 08-13-14, 10:03 AM
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New starter installed, no dice. I'm stuck
Dave
 
  #15  
Old 08-13-14, 10:17 AM
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I'd go back to the valves then and re-check. Are you sure they are set at .004 and not .040"? Does gas or mist blow out the spark plug hole when you crank it without the plug in it? Is the plug oily or wet?
 
  #16  
Old 08-13-14, 11:03 AM
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OK..I took off the valve cover and the top push rod was off the guide. Put it back in set it to .004 she turned over and ran for a few minutes, but it was real hard to start.The only way I can describe it is that it is "banging" or "thrashing" when I try and start it. It will do one or two revolutions and hesitate, stop then catch and turn over and run. . When it was running just now the engine sounds fine. It was running smooth and strong. So I am relieved that the engine is not damaged. I cut a few rows and then it just died again. As far as your questions...yes it is indeed .004 and not .040. No mist or spray out of the spark plug bore. Plug is not real oily, just smells of gas. So I guess it still must be the valve adjustment? What am I doing wrong? By the way, thanks for your patience!
Dave
 
  #17  
Old 08-13-14, 02:16 PM
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OK...I can get it to start up normally and run. It will cut about 60 feet of grass then it will die. I open the valve cover and either the top or the bottom push is out. They are not bent. I have done this 3 times. This engine doesn't have any way to lock the nut after you set the valve clearance. That is where I am at.
Dave
 

Last edited by truenorthdv; 08-13-14 at 02:42 PM.
  #18  
Old 08-13-14, 06:00 PM
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I found that 3 out of the 4 mounting bolts for the engine were extremely loose. That was the cause of the "thrashing" I described earlier when trying to start. At least that symptom is resolved. I thought that the excessive vibrations were causing the push rods to be dislodged? I was able to get it running and cut most of the front yard. I thought I had it licked...then, it died. I pulled the valve cover off and the top push rod was out. It was not bent or distorted. I can put it back together and the same thing happens. It will run and I can cut for a bit until the top push rod falls out. The rocker arm is not bent.
Very frustrating!
Dave
 
  #19  
Old 08-14-14, 09:25 AM
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This keeps bothering me...there are no set screws or torx screws to "lock in" the valve adjustment. Is this normal? Is this why the rod keeps falling out?Name:  valves.jpg
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  #20  
Old 08-14-14, 10:12 AM
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The adjuster nuts got tightened too tight with the torx screws still in place and the top of the nuts popped off under the pressure. It had torx screws at one time. If you'll look closely at the ends of the nuts, you can see the broken end facing you in the pictures. You need 2 new adjuster nuts and set screws. The broken pieces are probably in there somewhere. Also check to be sure there is a little cap over the valve stem where the rocker arm hits the valve on each one. If not, those are missing too and need to be replaced. It doesn't look like they are there in the pic.
 
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Old 08-14-14, 11:09 AM
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Wow! You are the man Cheese!!!!Holy smokes, I never would have known that. Thank you so much! I will take a picture of the top of the valve stem to verify if the caps are there or not. I could not find any pieces...I am not the first owner of this lawn tractor...but this all makes sense now. Thanks so much! Is my best bet to order from Tecumseh for these parts? I do have a parts diagram for this engine and can get the part numbers.
Again, Thanks for the advice....guess a picture is worth a thousand words!
Dave
 
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Old 08-14-14, 12:03 PM
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OK here is a picture of the valve stem. Is the cap missing?Name:  100_0733.jpg
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Also, a side view of the broken nut.(a bit out of focus)
Again, you were right on the money!Name:  100_0734.jpg
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  #23  
Old 08-14-14, 08:41 PM
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Nevermind on the caps, that's a different engine than I was thinking. Just get the adjuster nuts and set screws. Tecumseh went out of business, but you should be able to find them with a google search. Find the part numbers, then search them. I'm sure several dealers offer them.
 
  #24  
Old 08-14-14, 09:22 PM
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Thumbs up MTD Busted Rocker Arm bearings

Thanks Cheese.Found them online. New Tecumseh part number is 730636A if anyone ever needs them you will require 2 complete sets. comes with 2 rocker arm bearings and 2 set screws. Shipped in 4 to 7 days. Got it from Tecumsehparts store.com. I will report when installed.

Set screws are 5/16-24x1/4. Are those torx T-20?
Dave
 

Last edited by truenorthdv; 08-14-14 at 09:28 PM. Reason: puctuation
  #25  
Old 08-14-14, 10:20 PM
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I can't remember if they are t20 or t25.
 
  #26  
Old 08-20-14, 12:22 PM
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Alright then...Received the #730636A kit today and just wanted to check a few things before I install. Here is what is in the kit:Name:  100_0737.jpg
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Also the instructions:Name:  instruct.jpg
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The instructions did not scan too well, hope they can be read.
I assume the old rocker arm studs are just screwed in, in other words, I won't have to take anything else apart to install them will I? The other question is, do I really need a torque wrench? Finally, since there are no torx screws, I'm guessing the jam nut is how you lock the .004 setting in. I know this is probably obvious to anyone who works on small engines, but I am totally lost when it comes to being a mechanic. Thanks again for your help.
Dave
 
  #27  
Old 08-20-14, 05:23 PM
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Apparently they updated them and this is what you get. I know many tecumsehs had jam nuts instead of torx screws. Yes, the old studs screw out. You may need to put 2 nuts on them and jam them together to be able to have a "bolt head" to put a wrench on to screws the studs out. You don't need a torque wrench if you use judicial pressure when tightening the studs. You don't want to strip them out or leave them too loose. Tighten them like you would any bolt that size and you'll be fine.
 
  #28  
Old 08-21-14, 02:49 PM
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Problem Solved! Thanks Cheese!

Installed the kit and set the lash to .004 and she started up fine .
Cut the whole yard without any problems.

I learned a whole bunch about small engines the past two weeks.

Thanks Cheese, for keeping a 17 year old mower running!
Dave
 
  #29  
Old 08-21-14, 04:59 PM
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Great! Glad I could help you again!
 
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