Briggs and Stratton 17.5 hp idle

Tedtractor

New User
I have a 17.5 hp Briggs and Stratton that won't idle down while the mower is not engaged, once I engage the mower belt the engine idles correctly ... any ideas?
 
Can you make it idle down by pushing the throttle closed on the carb?

If so, either the throttle cable is out of adjustment and not returning the carb to idle, or the governor is out of adjustment. Try the throttle cable first.

If closing the carb by hand won't bring it down, check for a vacuum leak, loose carb bolts, sucked in gasket. Could also be the throttle plate is loose, bent, or improperly installed on the shaft.
 
(quoted from post at 12:42:35 05/27/18) Can you make it idle down by pushing the throttle closed on the carb?

If so, either the throttle cable is out of adjustment and not returning the carb to idle, or the governor is out of adjustment. Try the throttle cable first.

If closing the carb by hand won't bring it down, check for a vacuum leak, loose carb bolts, sucked in gasket. Could also be the throttle plate is loose, bent, or improperly installed on the shaft.

If there was a vacuum leak, how would the engine idles correctly when the mower belt was engaged?
 
Maybe very slight leak that would raise engine rpm. You maybe dragging the rpm back down with the load of the blades. But it could be several different things causing it.
 
Is this a new occurance? Idle while not under load
is intentionally high on mowers. It can be set by
moving the cable at the carburetor, however, it
then may not fully close the choke for a cold
start.
 
Hello Ted tractor,

Adjust your idle speed. The reason it does not faulted with
the blade engaged is because the governor is taking over the
extra load. Let me know if you need help adjusting the idle
speed,

Guido.
 
Hello Pete black,

Idle is adjusted with the idle screw on that model B&S,

Guido.
 
(quoted from post at 15:42:41 05/27/18) Hello Ted tractor,

Adjust your idle speed. The reason it does not faulted with
the blade engaged is because the governor is taking over the
extra load. Let me know if you need help adjusting the idle
speed,

Guido.

If you could explain how to adjust the idle correctly I would appreciate it. Thank you
 
yes, you are correct, however the length of the cable clamp at the carb terminal impacts the the throttle opening which may limit the lowering of the idle speed. another however, this b&s model may be different.
 
Hello Pete black,

The cable adjustment is for proper choke and full throttle adjustments,

Guido.
 
Another however, on my koler 22 hp I reduced idle speed by repositioning the cable at the carb, it did allow lower idle speed. At full throttle the choke would not completely close for cold start so moved cable back to factory, choke worked but again high idle speed.
 
Hello Pete black,

In the picture you can see the idle adjusting in the back of the black cap. That is the idle screw in A 17.5 H. P. B&S. The black plastic limiting plastic stop is over the mixture screw,

Guido.
a268986.jpg
 
Hello Tedtractor,

Your model engine idle is set @ 2200 R.P.M.s To adjust the idle you simply turn
the idle screw. If you need to adjust the mixture here is the procedure:
Adjust the idle to 1750,R.P.M.'S, then carefully pry up the mixture screw
plastic limiting cover. While watching the tack, turn the mixing screw until you find
the rpm's where the engine stumbled both ways, while counting the turns. Hold the
idle lever in to make sure it is against the idle screw, that way you will
maintain the 1750 you just set
rpm's. Now turn the idle screw 1/2 way. Put the adjusting screw cover back on with the stop tab
between the stops. Return the engine idle to 2200 rpm's. You can adjust the mixture @2200, but it will be too rich if you do it that way. Let me know if you need more help. Just star a new thread,

Guido.
 

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