[twogunsll]

Hi All,
I'll try to make this short.
My mower started with some sort of ticking/clattering sound. It got a little loud at one point then settled down a bit. All of a sudden lots of lt.blue/white smoke started coming from what looked like the front of the motor near the valve cover. I noticed lots of old oil around the valve cover due to loose bolts (I think). Anyway, I did a valve adjustment and put everything back together and started her up and it sounded real good. In fact it sounded better than it did for a long time. I started cutting grass and after 5 minutes the engine revved up as if I full throttled the machine. I tried to Idle it down but got no resopnse from the throttle control. Throttle control is working properly, always had and I never touched it. It was like it was posessed or something. The only way I could stop it was turn the key off. Can anyone help me with this problem?

 

[Mark777]

What type and model mower is it?

<edit> OK, never mind....I see your intro - Welcome to MLMF BTW...

So, what model and type engine do you have in your Craftsman...and is it a single or two cylinder engine?

 

[twogunsll]

What type and model mower is it?

<edit> OK, never mind....I see your intro - Welcome to MLMF BTW...

So, what model and type engine do you have in your Craftsman...and is it a single or two cylinder engine?

Hi Mark, I have a single cylinder craftman 18.5 Hp Intek with 42" cut. I checked the throttle control and everything is good. All linkage is working properly. Engine stays wide open till I turn the key off or choke it out.

 

[Mark777]

twoguns,

If your carburetor float isn't stuck.....

It sounds very much like you have a governor spring issue. It, or the governor may be broken. This happens frequently and you may be able to spot this (spring). If it isn't the spring it may be the governor shaft is broken.

This is where I would start to diagnose the WOT issues.

 

[twogunsll]

twoguns,

If your carburetor float isn't stuck.....

It sounds very much like you have a governor spring issue. It, or the governor may be broken. This happens frequently and you may be able to spot this (spring). If it isn't the spring it may be the governor shaft is broken.

This is where I would start to diagnose the WOT issues.

Ok Mark, Im going to check that out first will post again later.......thanks.......TG

 

[twogunsll]

Hey Mark,
I want you to take a look inside my valve cover,( if my pic loads up). I had this mower since 1995 and haven't adjusted the valves once. Don't get me wrong, I do take very good care of my mower by cleaning and maintenance. I just didn't know about the valve adjusting thing. I may have a valve issue but don't know what a burnt valve looks like. I know what a valve looks like just not a burnt one. When the engine is running it sounds good and no smoke. What would happen if I had a bad or broke ring or a stuck or burnt valve? What would be my engine symptoms with either of these problems.? Ok, so you can't actually see the valve but what about that burnt looking stuff around tha valve on the casing?

 

[twogunsll]

OK Mark, I checked out the spring issue and seems fine in that area. How would I be able to tell if the gov. shaft is broken?

 

[twogunsll]

Seems like the only problem I'm having now is the throttle going wide open at start up with no control over it from control level or down below at the linkage. I don't know what to do now.

 

[tmlong]

gov

It has to be a linkage or gov.problem.

 

[Mark777]

It has to be a linkage or gov.problem.

I agree -

I can't think of a single problem relative to WOT that isn't related to throttle linkage or governor. Hate to suggest that you start the engine and fiddle with either when it's running at such a high RPM...sure don't want you to blow it up.

I'm nearly convinced that something is being overlooked and the problem is mechanical. Check every inch of the carburetor throttle and choke linkage to be sure they're working freely and independent from the cable. Once you're satisfied that the problem is, or isn't with the carb linkage, then it must be a weak or over-stretched governor spring (or broken gear lobe on the governor shaft inside the case).

RE your rocker arm picture, You may have poorly adjusted valves from the exhaust gasses leaking around your exhaust valve. This certainly would add to poor performance and lower compression, but nothing I could relate to the WOT issues...

 

[Mark / Ohio]

Only thing I might try would be starting it while holding the throttle linkage against the idle stop. If it still takes off I would guess either the throttle plate inside the carb has come loose from the shaft or there is a vacuum leak between the throttle plate and the engine. But if a vacuum leak was the cause I would think it would lean out and stall pretty quick.

At least that would prove out whether it is an internal carb issue instead of a governor or linkage problem.

 

[twogunsll]

OK Mark, Thanks for all your help. Looking at the valves that how they looked when I took the cover off the first piror to setting them and she was running bad with lots of backfiring. It's running alot better except for the wot. I can't see anything wrong with any of the cable or linkage fro the throttle so my guess is the gov. broke insised the case as you suggested. That means taking the whole motor apart to fix it right? Ca it be fixed?

 

[twogunsll]

I agree -

I can't think of a single problem relative to WOT that isn't related to throttle linkage or governor. Hate to suggest that you start the engine and fiddle with either when it's running at such a high RPM...sure don't want you to blow it up.

I'm nearly convinced that something is being overlooked and the problem is mechanical. Check every inch of the carburetor throttle and choke linkage to be sure they're working freely and independent from the cable. Once you're satisfied that the problem is, or isn't with the carb linkage, then it must be a weak or over-stretched governor spring (or broken gear lobe on the governor shaft inside the case).

RE your rocker arm picture, You may have poorly adjusted valves from the exhaust gasses leaking around your exhaust valve. This certainly would add to poor performance and lower compression, but nothing I could relate to the WOT issues...

Hi Mark,
Well, I talked with the crane macanhic at work today about my lawn mower. He told me that I have my valves set too tight and that's whats causing my throttle to go wide open. The reason is the exhaust is building back pressure in my crankcase causing the gov. to go wide open. He said the gov has something like a small centripetal clutch type thing on the shaft that when the pressure builds up it causes the theig to open up making the mower go wide open. He also said that if the gov. shaft was broken the enging would not go past idle, and could never go wide open. So What I need now is to find the correct valve setting for my mower. Thanks for all your help mark and the others here on this great site. I'll be chatting with yall now and then.
ps. I just bought a new craftman 2 cylinder 24 HP.

 

[Mark777]

I agree with your crane mechanic. The end of your governor has a fly-weight inside your case, which opens with throttle. I hadn't thought about tight valves creating crankcase pressure....

Good luck!

 

[Mark / Ohio]

Well, now that is an interesting theory. It also does play in since you had just adjusted the valves. But I must say I'm pretty skeptical about it for several reasons.

(1) Any engine I've seen with an exhaust restriction lost power and would barely run. Like any air pump if they can't exhale, they can't inhale and vise versa.

(2) If you have high back pressure in the crankcase it ought to be bleeding oil from the seals and breather.

(3) The governor is only concerned about how fast it is spinning and the resulting centrifugal force on the spinning weights. I can't see how internal atmospheric pressure could possibly be high enough to hold the weights in on the gear. After all this thing has to work with oil spraying all around and coating it.

(4) The governor spring is constantly trying to pull the throttle open. The governor itself depending on the speed then adds the opposing force to close the throttle.

Here's a document straight from Briggs:

http://www.tractorbynet.com/forums/...00-wont-idle-sounds-intek.v-twin.governor.pdf

Another explanation of how they work:

Governor Theroy

Keep us posted what you find on this.

 

[twogunsll]

hey again Mark
Twogunsll here,
Well, I re-adjusted my valves to the correct settings to see if my machinc at work was right. He was wrong. My settings are for intake .003-.005 and exhaust is .005-.007 well, I set the exhaust at .007 and the intake at .005 and it still went wot. I stopped it right away and set the exhaust at .010 and still wot. I give up. I don't see anything wrong with the linkage other than maybe something going weak on me. The only way I can slow the engine down is to choke it out using the throttle. As I'm doing this I'm looking at the carb and the linkage and gov. I have to move the throttle back and forth from the choke to run position in order to keep it from going wot. Doing this the engine is not stablized at all and the linkage,choke and gov are moving back and forth as I work the throttle in those positions.The only way to check the gov lobe or shaft would be to take the entire engine apart, right?

 

[Mark / Ohio]

...The only way to check the gov lobe or shaft would be to take the entire engine apart, right?

Unfortunately, yes. You would need to open it up and have a look inside the crankcase.