Throttle/Governor Linkage

D

Dave27944

Well-Known Member
Member
Good Morning,
This is my first post here at Tractor Fanatics. I am looking for some help with my mower engine. I was getting it ready for the upcoming mowing season and trying to solve a problem from last year.
The engine would run great but if, for some reason, it died, I could not get it started again while it was hot. Someone told me to check the valve clearances(0.004"). I did that. no help.
I have also purchased a new Carb. While putting that on I noticed that the linkage doesn't look right to me. The choke function seems to be working correctly but the throttle control butterfly on moves about an 1/8" from idle to full throttle.
Any insight on how to set up the throttle control linkage would be appreciated. I provide the following information:
The mower is a 2008. I am ASSuming that the engine is the same year(don't know how to figure that out).
Tecumseh
13.5 HP
Model Number: OV358EA
Engine Family: 8TPXS3582AA
Spec: 206940G
I do have pictures of the linkage if that would help.

Thank you in advance for any help anyone can provide.

Dave
 
I went thru a first in my life experience with a new B&S engine I installed on my chipper. It would start and run fine cold but if shut off for a few minutes it wouldn't start. After some diagnosis I finally found the spark plug, after soaking up heat from the head, would short out internally. Tried replacing the plug and same thing. Since it is a long reach plug I replaced it a short reach and problem solved. Still is a mystery to me.
 
ol' stonebreaker said:
I went thru a first in my life experience with a new B&S engine I installed on my chipper. It would start and run fine cold but if shut off for a few minutes it wouldn't start. After some diagnosis I finally found the spark plug, after soaking up heat from the head, would short out internally. Tried replacing the plug and same thing. Since it is a long reach plug I replaced it a short reach and problem solved. Still is a mystery to me.
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Thanks, ol'stonebreaker, I appreciate the response and I will look into replacing the plug and see what happens.
 
Dave27944 said:
Thanks, ol'stonebreaker, I appreciate the response and I will look into replacing the plug and see what happens.
Click to expand...
I should further explain that once the plug cooled down a bit it worked fine only to start the problem all over again once the egine was warmed up again. I found the problem by using a known good plug connected to the plug wire when it won't start and ascertained the ignition was making spark then pull the hot plug, connect it to the plug wire and found no spark. I guess the short reach plug doesn't absorb as much heat. My theory on this particular engine is the plug is only about 3/4" from the exhaust valve which is probably the hottest area of the combustion chamber.
 
Sawdust said:
First of all welcome aboard. Same here I’ve had these same symptoms three times and every time it was the plug.
Click to expand...
Thanks for the welcome and the confirmation of a possible problem, Sawdust. I appreciate your input.
Would either of you know about the linkage arrangement for the carb. I have ordered a new throttle linkage, governor rod and choke rod hoping that will help the operation of the engine. I am wondering about the setup for the governor rod connection. I am guessing that it matters what position the linkage rod is at for the governor to take effect. Does it angle 10°, 20°, etc forward from vertical or does it tilt towards the rear some amount of degrees? Any thoughts on that?
Thanks again,

Dave
 
ol' stonebreaker said:
I should further explain that once the plug cooled down a bit it worked fine only to start the problem all over again once the egine was warmed up again. I found the problem by using a known good plug connected to the plug wire when it won't start and ascertained the ignition was making spark then pull the hot plug, connect it to the plug wire and found no spark. I guess the short reach plug doesn't absorb as much heat. My theory on this particular engine is the plug is only about 3/4" from the exhaust valve which is probably the hottest area of the combustion chamber.
Click to expand...
That seems to make sense to me, stonebreaker. When you reference the "short reach plug" vs the "long reach plug" what is the approximate measurement of the long/short plug? I am not sure what I would ask for when shopping for a "short reach" plug.

Thanks,

Dave
 
You need to run a plug that when threaded in tight the beginning of the threads is even with the inner surface of the head. If too long you risk the piston coming up and hitting it, if too short it acts like one of those "spark plug non foulers", that held the spark out of the "breeze" of incoming fuel charge but can also erode the rest of the threads between the end of the plug and the chamber, and/or a ridge of carbon will build up at the end of the plug shell, where you'd never get the right plug for the engine back in there. Use the right reach for the engine at hand.
 
dodge trucker said:
You need to run a plug that when threaded in tight the beginning of the threads is even with the inner surface of the head. If too long you risk the piston coming up and hitting it, if too short it acts like one of those "spark plug non foulers", that held the spark out of the "breeze" of incoming fuel charge but can also erode the rest of the threads between the end of the plug and the chamber, and/or a ridge of carbon will build up at the end of the plug shell, where you'd never get the right plug for the engine back in there. Use the right reach for the engine at hand.
Click to expand...
Thanks for the response, Dodge Trucker. How would I determine the correct "reach" for my engine? I am unsure of the clearance between the piston at TDC and the electrode of the plug. If, as ol' stonebreaker recommends, I go to a shorter plug(the 0.250"), would that result in having the unused threads in the head exposed to the heat and carbon buildup during operation. Would the correct reach plug solve the problem of the engine not starting when hot or might there be another issue contributing to that problem? If the shorter plug solves the problem of the hot start condition, why would I want to go back to the longer reach plug?
Any thoughts on this would be appreciated. The ultimate goal is to solve the non-start when hot issue.

Thanks,

Dave
 
Dougt said:
You mentioned replacing the carb. Did you have the issue with the linkage before the new carb? Maybe the throttle lever is different?
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Hi, Dougt. Thanks for the response. I haven't run the mower yet this season. I have been cleaning up the deck, new blades, etc. I do remember, from last season, that I didn't notice much of a difference between full throttle and idle. When I was poking around, I noticed that when I moved the throttle lever from Idle to choke, the choke butterfly closed and seemed to be working fine. the other linkage, I am guessing is for the governor only moved about an 1/8" inch. I don't know if that is normal but decided to replace the throttle linkage, the governor rod and choke rod. The variable I don't know is how much the governor linkage moves when the engine is running or where to position the linkage for proper operation.

Thanks,

Dave
 
Maybe some comparison pics of the old and new carbs would help us help you. Specifically the throttle arms the gov rod attaches to. Was the engine RPM like this when you bought the mower? if so it could be someone who didn't know what they doing adjusted the governor arm to governor shaft improperly.
 
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dodge trucker said:
You need to run a plug that when threaded in tight the beginning of the threads is even with the inner surface of the head. If too long you risk the piston coming up and hitting it, if too short it acts like one of those "spark plug non foulers", that held the spark out of the "breeze" of incoming fuel charge but can also erode the rest of the threads between the end of the plug and the chamber, and/or a ridge of carbon will build up at the end of the plug shell, where you'd never get the right plug for the engine back in there. Use the right reach for the engine at hand.
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I posed this question about the plug shorting out when I found the cause of the problem and no one had an answer for it Should I buy one of each of different brands with long reach to see if the problem persists?
 
Dave27944 said:
The variable I don't know is how much the governor linkage moves when the engine is running or where to position the linkage for proper operation.

Thanks,

Dave
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If your gov lever is adjustable on the shaft, that has to be done first. You want the gov shaft against the gov and the throttle wide open with the engine not running. Once the engine starts the gov should pull the throttle to idle. Spring tension against the lever/throttle will determine the speed. The spring should be trying to open the throttle. Hope that makes sense.
 
A "good" plug should be easy to find in the correct reach for that engine.
The length of the threads wasn't the problem with whatever plug you had in the engine. The particular plug was probably defective. Unscrew the plug and simply look at how deep the head is, how deep it is threaded. You should be able to look up the right plug for that engine (don't go by equipment manufacturer) companies like yard man, MTD, craftsman, cub cadet don't build engines, they buy them. A "craftsman" Briggs and a "Deere" Briggs engine of the same series would take the same plug. If all else fails take a piece of wire ( paperclip unfolded, even) and hold it in the spark plug hole and "eyeball" the length of the threads off of that if you have to.
 
A B&S branded plug was what started my problem. Bought a Champion and it did the same thing. I can't recall the brand of the short reach one, It starts easy and runs well and most importantly it restarts when hot..
 
Thanks to all for the responses. I will try to address them as I see them in this thread:
ol' stonebreaker: I do have some pics. However, I have already removed the old carb since the new one has arrived and I am preparing to install it. I will put the old one back on and send the linkage configuration as it was....
Can anyone recommend a good plug manufacturer for the Tecumseh engines?
Dougt: Yea, that makes sense. The lever IS adjustable on the shaft. I have been on Youtube watching some videos on the governor operation/adjustment and I understand the mechanical operation of the governor. Everything I watched seemed to suggest that the governor shaft, where it penetrates the casing, should be turned counter-clockwise as viewed from the side, to come in contact with the governor spindle inside. Does that sound correct?
Dodge Trucker: The length of the threaded end of the plug is about 5/8", which, I am guessing, is the correct reach for that engine. Any recommendations for a website that would provide the correct information? I have been running a Champion RS12YC plug.

To all: I was speaking with a guy at the auto parts store, who also provides lawn mower repair parts here in NC, about the issue of non-start when hot and he made some suggestions such as checking valve clearances(which I have verified) and also that a contributing factor could be the cooling fins around the head could be clogged up with dead grass, dirt, etc preventing the desired cooling effect. I checked that out last night and there was quite a lot of trash clogged around the heat shield and in the cooling fins. I have cleaned them out(Either way, I'm sure that keeping that area clear of dirt and debris would be a good idea.....). He also said that one contributing factor could be the ignition coil.
Any thoughts?
I will try to get some pics uploaded today, by tomorrow for sure.

Thanks,

Dave
 
As I said when it wont start hot have a known good plug handy to sheck ignition spark, if so remove the plug and check it for spark. If it has spark it's not the problem. Time is of the essence for this test 'cause when it cools enough it will spark again.
 
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