Throttle lever on carb forced wide open by governor

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  #1  
Old 10-01-04, 06:44 PM
DSGarcua
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Question Throttle lever on carb forced wide open by governor

I was having problems with my B&S 2 cyl engine for my riding mower. Running rough, burning rich, black sooty smoke, etc. I cleaned the air filter, replaced plugs, fuel filter, needle valve, cleaned carb (twice), adjusted the tab on the float, etc. I could not figure how to get the seat out since there was no way to pry or twist it out and no way to poke from behind (any ideas?).

After putting the whole thing back together after disassembling the carb for the second time, I still had the problem. After starting, then engine ran fine, that is for awhile until I put it in gear (under load).

I discovered the problem was NOT the carb (probably). I noticed the throttle on the carb was pushed wide open, but the engine was rough and giving off black sooty smoke. Pushing on the governor lever a few times cleaned up the problem--the engine settled into running great. That is of course, until put under load. Again messing with the governer lever (that connects to the throttle lever on the carb) while the engine was running brought everything back into line. It seems like it wants to push the throttle wide open and then too much fuel causes it to burn rich and I guess since it is not reving up to speed due to the (rich rough running) it keeps the throttle wide open.

I know nothing on how the governor works other than it is between the throttle control lever on the dash and the throttle lever on the carb and that messing with it makes the engine run smoothly again.

The governor springs appear proper and the governor does not look like the adjustment has been changed. The problem started rather suddenly. I took off the outer cover off the engine and the magneto looks fine (note that the engine runs/plugs fire properly until put under load). Someone mentioned that the governor needs airflow to operate properly, but I don't know where it comes from.

What gives and what do I do now? Everything runs fine until I want it to go to work.
Thanks,
Dale
 
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  #2  
Old 10-02-04, 01:16 AM
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Hello Dale!

You still have carburetor problems.
The governor does not control the engine speed. The carburetor controls engine speed, and the engine speed controls the governor. The governor is trying to compensate for a carburetor problem that you have. Try running the engine with the choke partially closed. If it runs well, then the engine is running too lean. If it worsens, then it's running too rich. The seat is pressed in, and has to be removed with a self-tapping bolt. The seat doesn't generally cause problems on these, but could. Check where the float hinges on the carb top. I've seen some carbs with burrs or rough spots that interfere with the float operation. A quick touch with a file cures the problem.
 
  #3  
Old 10-02-04, 05:48 AM
DSGarcua
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Thank-you for the reply. It will be over a week before I will be able to get back to the engine problem again, but I will get an ez-out and remove the old seat and replace that. The float appeared to work smoothly the last time I had the carb apart, but I will check that also. (I cleaned all the little passages with a fine wire at that time.)

I am a little confused why the problem would be needle valve/float related. If that were malfunctioning, would it not still give me problems before I put the engine under load? The engine runs smoothly and does not act up until I put the engine under load (like driving the mower or engaging the blades). For example, if I engage the blades, then as normal, the engine slows momentatily under the new load while the blades pick up speed. However, now, the throttle is being forced open and held open by the governor instead of recovering. I had not tried to force the lever back into place while the blades are running because of the interlock that shuts it down if I get off the seat while the blades are running.

I am confused because everything runs fine while not put under load. I can conceive of the problem still being carb related, but perhaps something to do with the jets, or something after the fuel is in the resevoir. Is there anything else I should be checking the next time I take the carb apart?

If I get to the point where I am going to pull my hair out, do you think buying a new (rebuilt) carb and replacing the whole thing will give me an almost 100% chance of the thing working again.
Thanks,
Dale



Originally Posted by cheese
Hello Dale!

You still have carburetor problems.
The governor does not control the engine speed. The carburetor controls engine speed, and the engine speed controls the governor. The governor is trying to compensate for a carburetor problem that you have. Try running the engine with the choke partially closed. If it runs well, then the engine is running too lean. If it worsens, then it's running too rich. The seat is pressed in, and has to be removed with a self-tapping bolt. The seat doesn't generally cause problems on these, but could. Check where the float hinges on the carb top. I've seen some carbs with burrs or rough spots that interfere with the float operation. A quick touch with a file cures the problem.
 
  #4  
Old 10-02-04, 11:10 AM
Azis
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Having pulled the carb and cleaned, have you adjusted your needle screws since? If so what steps or how?
Replacing the seat would be (IMHO) an extreme step at this point, if in question, you can bench test the needle and seat. With the fuel bowl off, install the needle and float assy, use a catch can and holding the carb with the float held up, attatch a fuel supply to the inlet of the carb. If while the float is held up with slight pressure there is no fuel coming out, your needle and seat should be ok. Release the float a bit to confirm you have fuel supply......
If the seat does need replaced, do as cheese mentioned using a self tapping screw. An EZ out is designed to "unthread" a threaded bolt. The seat is pressed in. While being able to turn the seat may aid in removal, you will want something to pull up on. An EZ out will most likely pull out of the seat where a screw or bolt will not.

Also, a hazzard with using wire to clean passages, most are too small to accomodate all but the finest wire. Also most passages will have bends etc. The possibility off wire breaking off or even gouching may cause more problems than solved. A bath in some good cleaner and compressed air should be good.
 
  #5  
Old 10-02-04, 03:28 PM
DSGarcua
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I don't know anything about needle screws.
Dale

Originally Posted by Azis
Having pulled the carb and cleaned, have you adjusted your needle screws since? If so what steps or how?
 
  #6  
Old 10-03-04, 02:35 AM
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Your seat is probably fine. I think the engine is running too lean. the adjustment needle screw Azis mentioned is in the front of the carb, low near the base under the fuel bowl area. Try backing it out 1/4 turn.
 
  #7  
Old 10-03-04, 06:24 AM
DSGarcua
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Sorry but this engine does not have fuel mixture adjustment. It has an idle adjustment and an idle stop, but no traditional adjustment. Idle adjustment does nothing in regard to the problem. As I said, it runs fine in idle and at even at the 'fast' position. The throttle lever on the carb is only about 1/4 open at full speed. When I put the engine under load (rider in gear to move or engage the blades), the governor then forces the throttle lever wide open. That is what causes it to burn so rich and run rough and give off the black sooty smoke. Pushing on the governor lever a few times to force it back where it should be (and in turn where the throttle lever on the carb back where it should be), makes everything run perfect again. It is only when the engine is put under load that the governor forces the throttle position wide open.
Thanks,
Dale

Originally Posted by cheese
Your seat is probably fine. I think the engine is running too lean. the adjustment needle screw Azis mentioned is in the front of the carb, low near the base under the fuel bowl area. Try backing it out 1/4 turn.
 
  #8  
Old 10-03-04, 09:22 AM
Azis
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2 cyl briggs on a riding mower? Can you post the #'s of your engine and maybe make and model of the mower? I have not ran across a 2 cyl briggs on a riding mower that did not have a mixture adjustment on the carb, so you have my curiosity up
Its sounds like you are compensating with the govenor lever for the lean condition, with the engine under load and at full throttle, the engine wants all the fuel and air it can get thus opening the throttle valve completely. This allows a full supply of air however it may not be getting enough fuel for the amount of air. This is usually solved by a mixture adjustment but could be caused by other restriction to the fuel supply as well. When you move the govenor lever it in turn closes the throttle valve reducing the amount of air until the fuel/air mixture is at a correct ratio

You should be able to do the same thing using partial choke.
Also check to see that your choke is operating properly, closed when closed and full open and held when not choked.
 
  #9  
Old 10-03-04, 11:37 PM
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I agree, model# of the engine is needed to be accurate here. I was guessing you had an opposed twin engine (which you might, but most have an adjustment screw except the later models). If you have a V twin intek, then you probably don't have a mixture adjustment screw.
 
  #10  
Old 10-04-04, 07:37 AM
DSGarcua
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Thanks for the suggestions.

Engine is B&S, Model 42A707, Type 123801, Code 9701035B. The engine is 18.5 Hp. The twin cylinders are opposed. The mower is a 46" Huskee. I got an Operating & Maintenance Manual and an Illustrated Parts List from the B&S web site.

The only adjustments on the carb are "Idle Speed Screw" and "Non-adjustable Idle Mixture Jet". Of course, I can set the position of the choke cable and the throttle cable. I am confused as heck since the engine runs great at idle and also when I give it full throttle. But, when I engage the blades or try to drive, as I said before, the govornor forces the carb throttle lever wide open until I force it back into place, causing it to run good again. I can't imagine moving the choke position would help since I would suspect at this point it needs more air, not less plus the fact that too much fuel is being forced into the intake. I don't recall specifically, but I think I did try choking the engine, and perhaps it made things worse.

I will be unable to work on the engine until Saturday this week and will have very limited Internet access this week, so I will try again this weekend.
Thanks,
Dale

Originally Posted by Azis
2 cyl briggs on a riding mower? Can you post the #'s of your engine and maybe make and model of the mower? I have not ran across a 2 cyl briggs on a riding mower that did not have a mixture adjustment on the carb, so you have my curiosity up
 
  #11  
Old 10-04-04, 08:11 PM
Azis
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On the illustrated parts list page 6 reference item 147 if your fuel pump has 4 screws, if yours has 4 screws page 7 item 147A.
Here it just happens to be called a pilot jet. You should be able to adjust it, back it out(CCW) 1 1/2 turns from lightly seated, then adjust 1/8 to 1/4 turn at a time.
Its also a good idea to remove it and the main jet for cleaning.
 
  #12  
Old 10-09-04, 01:33 PM
Badmamajama
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I hate to inform you but I had the same motor with the same problem and it turned out to be the valve seat came loose and blew up the motor on one side. To be sure do a compression test on both cylinders. If one has no compression, that is the cylinder with the blow valve seat. Hope it's not the case but that's what it sounds like.
 
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