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No throttle control on Briggs & Stratton 28u707 1174-e1 OPHV engine


jrmont's Avatar
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07-14-11, 05:49 PM   #1  
No throttle control on Briggs & Stratton 28u707 1174-e1 OPHV engine

No throttle control on Briggs & Stratton 28u707 1174-e1 OPHV engine

Here is what I observe on the is Craftsman tractor. I will refer to the throttle lever as the lever that the rider adjusts to control speed. The throttle at the carb is just that.


1) When the engine is off and the throttle lever is set anywhere from off to mid speed, the throttle at the carb is wide open and the choke is open.

2) When the engine starts, the throttle closes to the idle screw and the engine runs at idle.


From the above, it seems to me that the governor is working since only the spinning of the engine brought the throttle at the carb across its range.


3) I can adjust the throttle at the carb by hand and the engine runs nicely at all speeds.


4) As I turn the throttle lever from mid to high, the choke closes and the throttle at the carb does not move. Eventually the engine stalls.

From the above, it seems I have a governor problem because only the governor action moves the throttle at the carb on this engine.


5) I replace the governor spring and this did not help at all.

6) I adjusted the governor per the manual.

7) The user manual is ambiguous regarding the throttle cable adjustment. In my case, the hole in the governor plate lines up with hole A when the throttle lever is at mid position.

Am I likely correct to assume that the governor clutch is the cause even though it seems to do the job of closing the throttle upon starting the engine?

I was surprised (I am no expert) that the choke was wide open in the slow to start position. Don't I normally start my small engines by closing the choke when the engine is cold?

 
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07-14-11, 06:10 PM   #2  
Update - My repair manual say's that the hole A and the governor play should align when the level is at full throttle. I did that and I finally made some improvement. I can almost adjust the speed to get full throttle at the carb. Forcing the governor arm back gets me the rest of the way an I suspect that will happen under load.

The only remaining mystery now is that I don't see when the choke will ever close. The level on the governor never goes far enough forward to push the looped wire that connects directly to the choke. Can anyone explain when that action is supposed to occur.

 
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07-14-11, 07:06 PM   #3  
What it is on? Some mowers bend the tab that pushes the wire loop linkage for the choke so that it doesn't contact it. They do this so they can install a separate choke cable. Your throttle should come up and hit the choke loop and push it forward at the last tiny bit of travel.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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07-14-11, 07:54 PM   #4  
No throttle control on Briggs & Stratton 28u707 1174-e1 OPHV engine

It is a Crafstman 917.276.42 42" lawn tractor with 16HP Briggs & Stratton 28u707 1174-e1 OPHV engine. I think you are on to something. I wondered why the portion of the governor control rack (you called it the throttle) that is intended to contact the choke "pusher" seemed to be bent back onto itself. If I am to go by the adjustment instructions, I should leave the cable adjustment where it is. Then the only way to get the governor control rack to hit the choke loop and push it forward at the last tiny bit of travel would be to bend the governor control rack a little bit (needs about 1/2 inch to touch the choke pusher at full throttle.

Can you tell me what I am trying to achieve in that last little bit of travel? While running in my garage with the blades disengaged (no load so to speak), I have a good range of engine speed. I will also stop by Sears and take a look again at the same engine now that you told me what to expect of the choke control. Thank you for the quick reply.

This has been a mysterious one for me. My experience was with throttle cables connected directly to the throttle control on the carb.

 
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07-15-11, 09:40 AM   #5  
Loosen the throttle cable clamp screw. Put the throttle lever on the dash all the way up to full choke, then push the white plastic piece on the throttle control box on the side of the engine all the way forward... until there is no more slot showing for it to push forwards. In this position, the actuator should push the choke linkage forwards until it closes the choke. If it does not, the actuator part of the control rack needs to be bent forwards.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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07-22-11, 05:05 AM   #6  
No throttle control on Briggs & Stratton 28u707 1174-e1 OPHV engine

That is how it was set up when I did not have any throttle control. I checked an engine at Sears and it is set up as you described. I have been away for the week and I will get back to it if the temps cool down this weekend. Are you able to explain why the choke is open at startup and gets closed at high speeds? I expected the reverse. Meanwhile, the engine is running with good when cold with good throttle control though the choke is always wide open. I will see how it operates warm when I cut the lawn today.

 
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07-22-11, 05:42 PM   #7  
No throttle control on Briggs & Stratton 28u707 1174-e1 OPHV engine

OK - I spent too much time in the mechanical drawings section of the manual and not enough time reading the operating instructions or the labels on the dashboard.

The throttle control has an icon at the top of its travel that represents choke. It makes sense that when starting cold, you put the throttle contol all the way up to the choke position (closed). Once started, the throttle is to be backed down to the label that says "running position". At that point the choke is wide open as I expected it to be at max throttle. So, my throttle problem was simply a misadjusted throttle cable. Proper adjustment procedure is as you described. Proper operation is as described in the Users Guide. Thank you again for your response.

 
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