The Jack's Small Engines Forum - Join Our Online Community
Jacks Small Engines Lawn Mower & Power Equipment Forums
Community Stats
1 day 7 days 30 days Max. View More
Top Posters
  1. SRTsFZ6
    (41 Recent Posts)
  2. Merf49
    (7 Recent Posts)
  3. Mikel1
    (6 Recent Posts)
Most Active Threads
  1. Grease zerk
    (12 Replies)
  2. Poulan Pro High Wheel mower Chute problem !
    (9 Replies)
  3. Viper 99cc Head Bolt Torque specs
    (7 Replies)
Top Rated Posts
    There is no record available at this moment
Birthdays
4/26/2025
Jacoboy
2018/09/15 19:26:31
shinzon

Pressure Washer idles High

I have a Craftsman 580.752212 pressure washer powered by a Briggs 12S912-0122-B1 engine. I recently replaced the carburetor because of a bad needle and seat. The machine ran and worked fine for a few uses after the carburetor swap, but the last time it started idling very high (nearly 5k according to my tachometer) with no load, but maintains a good rpm with the trigger pressed and spraying water.
 
RPM on this machine is automatically regulated--no manual speed lever on the machine. The choke is also automatically operated by a thermostat.  Replaced the rusty governor spring with a new B&S spring, 793604, but the problem persists. I attempted a governor adjustment, but it made no change to the issue.
 
With the governor rod between my finger and no governor spring attached, I can feel it attempt to push the rod away from the engine (towards WOT) when I hold the RPM low, but I don't think I feel it pull back towards the engine (closed throttle) as RPMs increase.
 
What should i be looking at here?
 
Thanks!
6 comments Leave a comment
AVB
You might have a misunderstanding how a governor works. The governor spring pulls the throttle to wide open and the mechanical governor pushes the throttle to idle. So without the governor spring the engine should only idle. If you manually speed the engine up and governor does not push things back toward then the governor has failed or is out of adjustment.
2018/09/15 19:57:05
shinzon
AVB
You might have a misunderstanding how a governor works. The governor spring pulls the throttle to wide open and the mechanical governor pushes the throttle to idle. So without the governor spring the engine should only idle. If you manually speed the engine up and governor does not push things back toward then the governor has failed or is out of adjustment.



Greatly appreciate the response.

Yup, I get that. The spring holds the throttle wide open and the governor pulls the throttle plate closed based on RPM. When I removed the spring to test, I expected the engine to only idle, but for whatever reason, no matter where I manually hold the RPM, the governor attempts to push the throttle towards WOT, it never pulls the throttle closed as RPMs rise. It basically seems to be working reverse of what it should--pushing, not pulling, as RPMs rise.
 
So from what you're saying, this could be an out of adjustment, or failed governor?

I attempted a governor adjustment but saw no change in the problem. Viewed from the top down, the governor shaft coming out of the engine should turn counter-clockwise to close the throttle plate and lower RPM. With the throttle held wide open by the governor spring, I loosened the nut holding the rod on to the governor shaft, and adjusted the shaft clockwise as far as it could go. No change in the problem. 
 
Did I do the adjustment incorrectly?
2018/09/15 20:09:58
AVB
Before adjusting watch which the arm moves as you goes to full throttle at the carburetor. With you holding it at WOT loosen the the lock screw and rotate the shaft in the same as the arm moved going to WOT and retighten the lock screw. This would be the static governor setting.
 
Also verify that the carburetor throttle vane is correctly installed.
2018/09/15 20:39:07
shinzon
AVB
Before adjusting watch which the arm moves as you goes to full throttle at the carburetor. With you holding it at WOT loosen the the lock screw and rotate the shaft in the same as the arm moved going to WOT and retighten the lock screw. This would be the static governor setting.
 
Also verify that the carburetor throttle vane is correctly installed.


I attempted a governor adjustment as you directed with no change to the problem. At this point I suspect the centrifugal portion of the governor on the camshaft is broken. Looks like I'll be tearing into this engine.


2018/09/16 10:19:47
shinzon
Tore into the engine and found that the governor came apart--the arms and plunger were rattling around in the bottom of the crank case--and the oil splasher gear is missing a few teeth. I think the governor lever may be bent as well. Mystery solved.
 
I don't see any other parts in the crank case; how is the governor/splasher assembly retained to the camshaft? Does it just freefoat on the cam gear?
 
Thanks for your help, AVB.
2018/09/16 18:32:53
AVB
Basically it is attach to camshaft lower end and retain in place by the crankcase  cover (ie oil pan)
2018/09/16 20:28:23

Comments are closed.

Copyright © 1994 - 2016 Jacks Small Engine & Generator Service, LLC
© 2025 APG vNext Trial Version 5.5