Lawn Boy runs high rpm

[impalass]

When you had the carb off did you the reeds. With both carbs you have the same symptoms. Are the filters clean, you might two, one in the gas tank and the other in the carb. Depending on which carb you have one is in the inlet supply which is a small wire mesh tube and the other in the carb over the main jet.
When you cleaned the carb did you take out the main jet and checked the holes were clear. You have a very small hole near the top of the main jet.

 

[Mary Wilson]

When you had the carb off did you the reeds. With both carbs you have the same symptoms. Are the filters clean, you might two, one in the gas tank and the other in the carb. Depending on which carb you have one is in the inlet supply which is a small wire mesh tube and the other in the carb over the main jet.
When you cleaned the carb did you take out the main jet and checked the holes were clear. You have a very small hole near the top of the main jet.

The filter in the carb looked beat up so I just removed it. I blew through the line to the tank and it didn't seem stopped up. It's very possible I didn't get the carb as clean as I could have. I'll probably take it apart again because I put it back together with some of the old parts that I meant to replace but I didn't have them at the time. I'll do a re-cleaning in a day or two. I'll probably check and see if maybe I created an air leak when I took all the stuff off the engine. Maybe a bolt hole letting air in?

 

[Two-Stroke]

I don't think running too lean will cause the symptoms you describe. The governor should still cut in and close the throttle at the same rpm. A photo of the carb (governor area) would help. I believe the governor is the problem.

An in-line fuel filter (made for 1/4" fuel line -- a generic item -- not expensive) is a good thing to install even if you didn't remove the stock fuel filter.

A good fuel filter will prevent a lot of the problems that you read about on this forum. :thumbsup:

 

[Mary Wilson]

I don't think running too lean will cause the symptoms you describe. The governor should still cut in and close the throttle at the same rpm. A photo of the carb (governor area) would help. I believe the governor is the problem.

An in-line fuel filter (made for 1/4" fuel line -- a generic item -- not expensive) is a good thing to install even if you didn't remove the stock fuel filter.

A good fuel filter will prevent a lot of the problems that you read about on this forum. :thumbsup:

Could be, but I did find something which may or may not be a problem. I took it apart today again and took the carb apart and soaked it in carb cleaner. The carb looked pretty clean but could still be plugged somewhere inside, I guess. What I noticed is a hole. I stuck a wire in it and it went in pretty far (at least an inch) before it touched something. I don't know if it's a blind hole or an open ended one, I couldn't see into the hole because some other stuff was in the way, so I put a bolt in the hole anyway with some sealer around it. I'll let you know later if that's it or not. I've worked on a few hundred chain saws and I can tell you that a lean engine will turn more rpms for the same throttle opening, it's like having a second throttle only without any fuel. If the hole is too big, of course the engine won't run at all, but with a little hole it will run too lean which will kill a 2 stroke. As for the fuel filter, I probably have one. I usually buy them at flea markets.
I really like this little mower, weights very little, has a magnesium deck. I've been using it sparingly to mow a bank in front of the house, it kinda wears me out to use my other, heavier mower.

 

[impalass]

Could be, but I did find something which may or may not be a problem. I took it apart today again and took the carb apart and soaked it in carb cleaner. The carb looked pretty clean but could still be plugged somewhere inside, I guess. What I noticed is a hole. I stuck a wire in it and it went in pretty far (at least an inch) before it touched something. I don't know if it's a blind hole or an open ended one, I couldn't see into the hole because some other stuff was in the way, so I put a bolt in the hole anyway with some sealer around it. I'll let you know later if that's it or not. I've worked on a few hundred chain saws and I can tell you that a lean engine will turn more rpms for the same throttle opening, it's like having a second throttle only without any fuel. If the hole is too big, of course the engine won't run at all, but with a little hole it will run too lean which will kill a 2 stroke. As for the fuel filter, I probably have one. I usually buy them at flea markets.
I really like this little mower, weights very little, has a magnesium deck. I've been using it sparingly to mow a bank in front of the house, it kinda wears me out to use my other, heavier mower.

That could be a air vent hole. If that is a plastic carb you do soak it in a cab cleaner. Did you read the manual that i gave you a link to.

 

[impalass]

I had to use my wife's name to log on. Something wrong with my password or something. Tried opening a new account but it wouldn't work either so I used my wife's name and password. Joe

I'll try to get a few pics up, maybe later today. I did look while the engine was running and the air vane was going back and forth so it's not stuck and the spring appears to be working. I think my problem is the engine is running way too lean, either has an air leak or not getting enough gas. I've had several Lawn Boys over the years and most have done well for me. I bought this mower strictly for the deck and put another engine on it. The one I put on originally came with an electric start and bagger, self propelled, and I didn't use any of that stuff. I had to change the carburetor and top cover. I tried to make it like my Lawn Boy Utility except with an alloy deck. I tried a Walbro carb with choke instead of the primer and the engine ran exactly like it does now. Should I bother trying to change the upper crank seal? The number on the deck is S19ZPN.

https://lookup3.toro.com/Ill/1x/5/5707/80290005.gif

 

[Mary Wilson]

I had to use my wife's name to log on. Something wrong with my password or something. Tried opening a new account but it wouldn't work either so I used my wife's name and password. Joe

I'll try to get a few pics up, maybe later today. I did look while the engine was running and the air vane was going back and forth so it's not stuck and the spring appears to be working. I think my problem is the engine is running way too lean, either has an air leak or not getting enough gas. I've had several Lawn Boys over the years and most have done well for me. I bought this mower strictly for the deck and put another engine on it. The one I put on originally came with an electric start and bagger, self propelled, and I didn't use any of that stuff. I had to change the carburetor and top cover. I tried to make it like my Lawn Boy Utility except with an alloy deck. I tried a Walbro carb with choke instead of the primer and the engine ran exactly like it does now. Should I bother trying to change the upper crank seal? The number on the deck is S19ZPN.

I tried again today (Saturday) and it did the same thing. I took it apart again last week and cleaned the carb out thoroughly this time and blew it out with compressed air. New air filter, no leaks anywhere. The saw ran at low rpm for awhile, then as I was mowing the mower touched against a small tree and the motor sped up. I shut it off and tried starting it and was hard to start so I primed it and it started but ran fast. I then primed it some more and it slowed down but only momentarily. The thing just seems to me it's not getting enough fuel. I'm wondering now if the float might be sticking shut. I'm going to try to find a kit for it and see if it helps...kinda running out of ideas.

 

[WhyZed]

Hey Mary Wilson's Husband

I uploaded a 5 minute video and linked it to this post;
http://www.lawnmowerforum.com/lawn-...ommercial-6277-bricktop-1969-1970-1971-a.html
The problem you are having and the solution might be explained near the end of it.

Check it, hope that is the problem/solution..

Zed

 

[Mary Wilson]

Hey Mary Wilson's Husband

I uploaded a 5 minute video and linked it to this post;
http://www.lawnmowerforum.com/lawn-...ommercial-6277-bricktop-1969-1970-1971-a.html
The problem you are having and the solution might be explained near the end of it.

Check it, hope that is the problem/solution..

Zed

I watched your video and I can tell you that my problem is nothing like that. Mine appears to be a lean condition but I can't tell from what. As of today I've changed both crank seals, changed the carburetor from a LB that was running fine, checked the block for leaks visually only (maybe I need to rig up a crank pressure tester) and still the engine runs wide open. I looked at the carb while it was running and the governor has the carb butterfly closed. I'm almost to the point of buying another mower and using this one for parts.

 

[WhyZed]

I watched your video and I can tell you that my problem is nothing like that. Mine appears to be a lean condition but I can't tell from what. As of today I've changed both crank seals, changed the carburetor from a LB that was running fine, checked the block for leaks visually only (maybe I need to rig up a crank pressure tester) and still the engine runs wide open. I looked at the carb while it was running and the governor has the carb butterfly closed. I'm almost to the point of buying another mower and using this one for parts.

Ok, I was hoping that was the problem.

Have you checked or changed the gasket between the carb and the reeds? (Sorry I didn't re-read the entire thread).
Other then that, I would agree, a leakdown test to find the air leak.