My Tractor Forum banner

Briggs 12hp IC - Can't adjust throttle when running

8K views 113 replies 10 participants last post by  demonspeed 
#1 ·
I tried searching for this one, but every combination of words I tried kept taking me to adjusting the governor, but I am not sure that's my issue. This is for my Bolens, btw...

I have no issues adjusting the throttle when the engine is off. Everything seems to move without issue -- no hang ups or anything -- with full engagement from the lever all the way through to the valve on the carb. As soon as I start the engine, though, it just sits at idle. Everything moves fine up to the governor spring. The spring moves, but nothing past that point.

Any suggestions? I can try adjusting the governor due to it being "stuck" (albeit at idle rather than the apparently normal full throttle), but why would it move freely when the engine is not running?
 
#2 ·
Sounds like either the governor has failed inside the engine or the linkge from the gov. shaft to the throttle is out of sync. Reset your static Gov. shaft to arm setting and go from there.

The throttle will apply spring pressure to the Gov-to throttle arm and the Governor runs the show from there.. Aka- You set the speed @ mid-throttle and when a load is applied the gov. opens the throttle until the previous speed is attained.

Hope this makes sense to ya..
 
#4 ·
Sounds like either the governor has failed inside the engine or the linkge from the gov. shaft to the throttle is out of sync. Reset your static Gov. shaft to arm setting and go from there.
Basically readjusting the governor per the B&S procedure then?

what is your definition of idle?and do you mean speed stays the same with control lever set for both slow speed and fast speed
Choke off and engine running with throttle blade closed.

And yes, that's exactly what's happening -- it just stays at idle no matter how I move the control lever.

Again, this is only when it's running -- the throttle blade opens and closes when it's off when using the control lever.

Maybe I'll go make a video...

Sorry if some of my terminology isn't perfect -- this is the first small engine (and carburetor) I've ever messed with (I'm used to dealing with later-model EFI automotive).
 
#5 ·
Please overlook the mess -- I never cleaned it up after doing fall cleanup last year. And just for perspective, I inherited this tractor as it's been around the family for many, many years. I'm just the first person to attempt getting it back in running condition. Last year I cleaned everything the best I could, rebuilt the carb, ran all new fuel lines, fixed some wiring, etc. It still has a long way to go, but I just need it for bagging and pushing slush.

With that out of the way, lol... :00000060:

Engine Off:
https://youtu.be/FFTlc6NxbUY

Engine Running:
https://youtu.be/IL_tSf-hdaQ
 
#9 ·
Well, I replaced the governor spring, lever, and link spring, adjusted the governor per the instructions (governor crank all the way right, WOT, tighten lever...), but it is still doing the same thing. The governor lever moves just fine when the engine is off, but won't move at all when it's running.

While parts for this thing aren't too costly, I am getting tired of messing with it. I thought maybe the next thing would be the internal crank bits, but that moves freely when it's off.
 
#10 ·
demonspeed:The governor lever moves just fine when the engine is off, but won't move at all when it's running.

The throttle linkage is designed to pull the throttle plate open when you move the lever to high speed. The only connection from control to throttle plate lever should be a spring. The spring is attached to the control lever that the cable connects to at one end, and the other should connect to the throttle plate lever. The spring should be doing the actual opening of the throttle plate.
The governor will pull back against the spring pressure once the engine starts by moving the governor lever, which moves the hard link connected to the throttle plate lever. If the governor didn't work, the spring would keep the throttle plate wide open until it broke.
I looked at both videos. It appears the governor is doing its job. You move the linkage using the cable control, rotating the levers behind the plate where the cable is attached, which *should* add/release spring pressure to counter the governor force produced when the engine is running.
If the hard link between the governor lever<>throttle lever is bound up with the spring link between the cable control<>throttle lever, the governor might keep the throttle closed, or pushed against the idle stop.
The throttle will generally not be wide open whenever the engine is not under load. It will be a lot closer to idle until a load is applied. Moving the control from idle to fast should increase the spring tension trying to open the throttle. The governor will, should, pull the throttle towards the closed position once the engine starts if the governed rpm is reached. It appears to be doing that.
The only question remains is whether the engine is at proper governed rpm or not. In addition, when you add load, the governor should 'relax' a bit, and let the throttle spring open the throttle to provide more power.
Try watching the throttle when you engage the blades. It should 'bobble' a bit as the load is added, then the spring should open the throttle, rpms increase, and the governor should then try to close the throttle.
tom
 
#11 ·
From what I'm understanding based on your reply, tomw0, I should have a separate link from the throttle mechanism (by the governor mechanism) to the throttle setup on the carburetor - correct? If it is the latter, I do not have that (which can be see in the videos). The only thing operating the throttle valve is the governor setup -- I have nothing else going to the carb for the throttle.

If this is true, I don't know how I ever used this thing in the first place. I mowed with it all last year -- and my family used it for years before that (albeit, neglectfully). Why would it now all of a sudden not be working...
 
#13 ·
so when it is running is the governor lever to the full left?
if you physically moved it to the right does the engine speed increase. if you have it set right the governor spring would be pulling the lever to move right (cw). the internal governor turns it ccw as rpm increase.
 
#14 ·
ok just watched engine off video again. when set to max speed and governorlever is full right. push it back to left. you should feel strong spring resistance to doing that. it is that spring tension that will stop governor from moving lever to left idle position. if you don't feel that tension then governor spring is not working right. might just mean that its connectiontab needs bent to increase tension
 
#16 ·
What is the model number of the engine? I assume that you used it to yet the correct governor spring. I just looked at manual and it really doesn't have a good picture of exactly where the governor spring is attached. I know one end is in the governor lever and the other in the bendable lever that moves with the throttle control.
 
#18 ·
speed:I should have a separate link from the throttle mechanism (by the governor mechanism) to the throttle setup on the carburetor - correct? If it is the latter, I do not have that (which can be see in the videos). The only thing operating the throttle valve is the governor setup -- I have nothing else going to the carb for the throttle.

Well, I just looked again. There are TWO things connected to the lever that opens the throttle. One is a hard link - a metal rod - which I assume is attached to the governor or the engine control linkage. The other looks to be a spring, attached lower on the lever than the rod. The spring may be used to to keep tension on the link between governor and throttle plate, and actually does nothing to move anything at all.
If that is the case, then all the governor-linkage spring action takes place back near where the control cable is attached. It will be a spring, again, tensioned more or less by the position of the control as moved by the cable. The governor will oppose the spring, and try to close the throttle when the engine starts. If the spring is set to idle, it will not oppose the governor. If the spring is set to full throttle position, it will pull harder against the governor. IOW, the governor lever should allow the control to fully open the throttle, which it seems to do in the video. Once the engine starts, it appears the governor pulls the throttle towards a more closed position. Which it should.
With the engine running, the throttle will not be wide open. It should vary position as the spring tension opposes governor movement. If you tried to move the governor lever by hand with the engine running, you'd find it was not easy to do.
I guess I am not seeing the problem. Have you used a tachometer to determine current rpm? If so, what is it? I cannot determine engine speed by sound to know if it is too fast or too slow.
When you move the control towards 'slow' does the engine speed decrease?
tom
 
#21 ·
Yes,everything works fine without the engine running. That's what I tried to show in the first video. It did it with the 30 year old parts - and does it now with the brand new parts.
 
#22 ·
with engine off when you move throttle on dash from slow to fast can you see in behind the box on engine side that a short lever is rotating and pulling the spring and other end of spring is indeed attached to a hole in the governor lever?
when throttle set to slow you should be able to move governor lever from right to left with no resistance. repeat with throttle set to high speed. there should be significant spring resistance to moving it left. if not you have spring on wrong ,wrong spring,or its tab on rotating lever needs bent to extend spring tension. did you remove the control box from the engine?
 
#23 ·
with engine off when you move throttle on dash from slow to fast can you see in behind the box on engine side that a short lever is rotating and pulling the spring and other end of spring is indeed attached to a hole in the governor lever?
Yes

when throttle set to slow you should be able to move governor lever from right to left with no resistance. repeat with throttle set to high speed. there should be significant spring resistance to moving it left.
Yes, that is how it feels

did you remove the control box from the engine?
If by control box you a referring to the setup in the attached picture, then yes, that was removed and cleaned when I installed the new governor arm.
 

Attachments

#24 ·
Well I am assuming that the square holding z end of wire does move up and down with dash throttle control. My thought then is that it has to be that the tension needs to be increased on spring to overcome governor pull to attain increased rpm. You say governor lever is to the right with engine off and throttle control in fast speed. I assume that if you watch as it starts that the lever moves to the left (governor action). And the problem is not enough spring tension to stop it from doing that. I may have a 281707 on my bench and will just double check its setup.
 
#26 ·
demon:I just don't quite get why this would be an issue now when it hadn't ever done this before - especially after I installed a new spring.

If the spring is installed into the wrong hole in the governor arm or the throttle control arm, it will have different 'leverage' characteristics, and will not function properly.
Did you take a picture before you did the remove/re-install, and when you installed the new spring? I'd double check what hole is specified for each control piece.
tom
 
#27 ·
It's installed exactly how it was before I messed with it. Unfortunately, it wasn't working with that setup as of late, though - hence the reason I started this thread. I'm thinking a solution would be burn it to the ground lol
 
#28 ·
Before you give it a shot of 22, take the control 'panel' off the side of the engine so you can take a picture of the linkage, springs, governor arm, etc. A visible picture may give a clue as to what's happening.
 
#30 ·
Picture of the governor spring and where it clips to the governor arm and the control assembly. There is only one hole to mount a spring on each of those parts.

The new arm is identical to the one that came off. The spring is what the B&S parts manual stated is for this particular engine. There is red paint on it if that means anything.

I also sincerely appreciate all of the responses. It means a lot that everyone is investing any amount of time in helping me solve this problem.:trink39:
 

Attachments

#31 ·
I've done some more digging in the parts manual; I found that there are a few options for governor springs. The one I got, 260871 (792602 new number) is red and the description says 2700-3300 rpm. Does that seem low or no?

Another one is 260695 (796260 new number) is green. No RPM range indicated.

There is also 261126 (796261 new number) is yellow. No RPM range indicated

Lastly, 260902 is listed, but seems to be discontinued.

What do the different colors mean? How do I truly determine which is the best one to go with?
 
#32 ·
on briggs parts ipl part 206 governor spring for your engine would be 260871 if code is after 8710600 and 261129 if code is before 8710700. Your model and type are not listed for any of the other spring options. so it appears you have right spring if your code is after the 87......... 3300 is reasonable rpm for a rider.
 
#33 ·
So that rules out the spring being the problem. I bent the tab that the spring mounts to on the throttle control assembly (what you see in the pictures) "out" away from the engine slightly. Was the the correct thing to do? I figured that would give it more tension to pull on the governor to open the throttle.

Unfortunately, now I am getting no attempt at starting whatsoever. No "click" of the starter or anything. Battery is good (had it tested). Coil would be my assumption. I'll have to search some threads to confirm before I order one of those. I'm sure tired of throwing parts at this thing.
 
#34 ·
your assumption would be wrong. Coil provides spark, has nothing to do with engine cranking. Make sure brake is on and blades disengaged. Hopefully people here can help prevent you from throwing parts. Do you know what the starter solenoid is and where it is located on your mower.?Maybe tell us the make and model of mower
 
#35 ·
You're right! I thought about that after I submitted my response but it was too late for me to edit it. Coil would be one of the last things considering it's far down the line so to speak. I threw up my hands for the day, so frustration got the better of me. I'll check the brake switch, seat switch, solenoid, etc. the next time I'm out there.

But back to the throttle/governor... Since I've adjusted everything and it's still not working (and assuming my bending of the tab doesn't work), would the next step be opening up the engine and replacing the internal governor parts?
 
#36 ·
<<<<<<<----------- just shakes his head.. there's that assumption thing again... let's stick to the facts that the people r tryin to tell ya.. someone asked if u knew what a certain part was & what it did.. we didn't get an answer to that..
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top