Murray riding mower stalls when the clutch is released

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  #1  
Old 06-14-10, 05:33 AM
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Murray riding mower stalls when the clutch is released

I have a Murray riding mower (model 40507x8A) with a BS 12.5 (model: 28v707-1113-E1). The mower has been thrown to the side for about 3 years now and I decided to revive it from the dead. I put a new battery, fuel line, fuel filter, spark plug and cleaned the carburetor clean and it starts good now. Also had to replace a cracked hose that goes from the air intake to the engine. I also cleaned all areas from clogged grass clippings. Specially the governor area so all throttle arms are free of any clogs.

My problem is, when I release the clutch the engine gives up. The RPM drops and it stalls. After reading through the threads pro's suggests that it could be a seat switch problem. I dont know how to trouble shoot if its exactly the seat switch. According to the wiring diagram there are 3 switches on my mower. seat switch, PTO switch (for the cutting deck), and clutch break switch.

How can i tell if this problem is because of a seat switch not the clutch break switch? Any ideas? I dont want to replace all 3 to later find out its just 1 switch that needed replacement. Whats the easiest way to figure this out? any ideas are welcome. Thanks.

Also can some one tell me where the clutch break switch is at? I cant seem to find it on the mower any where. Didnt turn it upside down yet though. is it under the mower by any chance?


update: found the clutch switch, it was pretty hidden near the cutting deck underneath the frame. I removed the switch and tried starting the mower and it wont start. so i'm assuming the switch is working? FYI: park break was on so it should start. Then continued to clean the connection points and plugged the switch back on, and the mower started but when i released the clutch it died. So i'm assuming it must be a bad seat switch? how can i test that?
 

Last edited by kanchis; 06-14-10 at 06:23 AM. Reason: found the clutch switch
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  #2  
Old 06-14-10, 08:02 AM
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You should be able to check the switch for continuity, all though, from the info you have provided, I would agree the seat switch is the culprit.
If the brake/clutch switch was bad, the seat would need to be occupied to start the mower regardless of brake position.
If the PTO switch was bad, the mower would not start regardless.
The seat switch must be activated for the mower to run or start anytime the brake switch is NOT made, and for the PTO to be engaged, even with the brake on.
 
  #3  
Old 06-14-10, 08:19 AM
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might be two parts to the clutch/brake switch or 2 switches there. One handles start circuit to the starter solenoid, the other handle the kill circuit to the coil and acts as override to seat kill switch allowing you get off the seat as long as pto is off and parking brake is on.
PTO likely also has 2 separate switches , one in the starter circuit and one in the kill circuit. You need to be checking every thing in the kill circuit only. Look here to see the wiring diagram
Murray lt Parts Diagram Index for 40507X8A
 
  #4  
Old 06-14-10, 08:20 AM
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Thanks for the info. I can release the park break and press the clutch pedal and start the mower while sitting on the seat. Does this mean that the seat switch is working?
 
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Old 06-14-10, 08:23 AM
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Originally Posted by kanchis View Post
Thanks for the info. I can release the park break and press the clutch pedal and start the mower while sitting on the seat. Does this mean that the seat switch is working?
NO! That means the clutch/brake switch is working.
If the seat switch is working, you should be able to start the mower with the clutch/brake released while occupying the seat,(tranny in neutral) if not, I say the seat switch is bad.
 
  #6  
Old 06-14-10, 09:34 AM
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check out the wiring diagram for the kill circuit. It goes through both a brake switch and the seat switch. Either there is a problem with one of the switches or a short circuit to ground in the circuit that can ground the coil based on the brake switch position in the circuit relative to the short location.
 
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Old 06-14-10, 10:58 AM
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It does look as though the clutch/brake does have to be engaged to "start", however not to "run".
As long as the seat switch is working and "occupied", the clutch/brake position and switch should have no effect once it is started.
I aint the best at chasin silly lil lectrons round a schematic but I have done a couple three of these. It is just a crude form of ladder logic, "if" "and" "or" just no PLC makin the decisions.
Still putin 10 on red seat switch
 
  #8  
Old 06-14-10, 11:16 AM
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After further thought on this, the clutch/brake switch could cause the kill circuit to function, but again, only if the seat switch is functioning.
To "start" the clutch/brake switch has to be working on one pole, and to "run" with the seat "unoccupied" the other pole has to be working.

Thx for the lesson 38 Beer 4U2
 
  #9  
Old 06-30-10, 06:36 AM
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Thumbs up

Wanted to update my post here with the latest info.

The seat switch is on order and I'm getting it today! (took 2-3 weeks since its OLD!) I started playing with the wiring harness yesterday and and tried disconnecting different wires and tried to run it and finally it worked! When I removed the wire that goes from PTO switch to the seat switch it didnt stall anymore! I'm not too good with troubleshooting electrical stuff so I dont know how to explain why or why not it worked. All I care is that the mower runs! After getting it to run I saw that the carb was getting flooded with fuel. Though I cleaned it out before the valve float needle seems to not be working I think. (there was fuel in the bowl too) I may have to buy a carb rebuild kit for $35 and put new parts in it and see how it goes. A new carb is $95 (Nikki) so I want to see if it's worth even trying to fix this or would I be better off putting a new one in there since its been sitting in the rain and sun for about 3 years now. I'll try to post some pictures here if it lets me so you can see the condition of it. FYI: the valve float needle is the type where you have a rubber tip/seal for all you pro's, so not the metal tip.

The other thing I wanted to know is how to tune the carb? There's a slight backfire when the engine runs. Can someone guild me through this please? The carb I have is a Nikki carb and the B&S part # 694941 which was replaced by 699831.
Beer 4U2

Here are the pictures from my project:
http://s921.photobucket.com/albums/a...awn%20Tractor/
 

Last edited by kanchis; 06-30-10 at 07:46 AM.
  #10  
Old 07-05-10, 11:56 PM
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Sounds like the carb needs cleaning some more.
 
  #11  
Old 07-10-10, 11:09 AM
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Kanchis - I have the same problem. Did you install the new switch? I think in bypassing the seat switch you may have found a workaround, but once the new switch is in, you may not need to mess around with the carb. Let me know -- this exercise I'm getting with my push mower has got to stop!
 
  #12  
Old 07-20-10, 06:48 AM
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dmarek - I installed a brand new seat switch and its still doing the same thing, which means the seat switch was ok to begin with. There's something electrical wrong with the tractor and I cant seem to figure it out. But since I bypassed that switch it all works now so its just a safety feature that I dont have and I can live with that.

Latest on the carb - I think I need to get a new needle because some times the engine tries too hard to idle at low rpms. feels like the there's something clogging the carb or the breather assembly isnt working properly. When I removed the carb to clean I did notice alot of gunk on the needle and I cleaned it but I guess it still sticks sometimes, so I'm going to give it a try with a new needle which is ordered already for $10 and see how it goes.

FYI: the engine the other day started making a loud noise liking hitting something at very low rpms. I think the engine bolts have come lose for some reason. I hope its not the rod!!! If it is, i'm giving up on this mower and throwing it to the dump!!! Hopefully i'll get around to it this weekend to tighten the engine bolts and see if the problem persists.
 
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