B&S 40s877 Governor help

If you can find the Briggs & Stratton ISO repair manual (CDrom), it has a section on the 40S877, or at least it responded as if it did when I typed in that model number.
I am pretty sure the ISO file(a CD in 'file' format that can be used to burn a CD) is available from a link on mytractorforum.
I could look through it, but cannot really compare what I find to what you see in front of you.
Have you checked that the governor arm actually moves, and has 'limits' in its travel? If the arm flops around like a Bluegill, then the internal governor could have self-destructed. It should have limits, and it should want to pull the throttle closed IMMEDIATELY upon engine start. The throttle control should pull the throttle plate wide open when in CHOKE or at FAST/Rabbit, and the engine should start with it open like that, and then the governor take charge right away, and pull it closed. If the governor arm does not move at that point, likely broken inside. Could be a loose clamp, but the shaft should rotate.


Searched bookmarks. The ISO came from here:

https://www.dropbox.com/s/ovpbw3oobuyizbh/Briggs & Stratton Repair Manual_All Models.zip

Dunno if still available.

tom

Thanks Tom, I received permission from the owner of the 20hp motor to remove the sump and check the governor , once the oil was drained and I put the motor on it's side , I could hear metal rattling around in the engine. I removed the sump, and sure enough the governor weights had flown off the governor , and were busted up inside the engine . I used a magnet to get the pieces out of the residual oil. I then referred to the manual to remove the governor assembly , the book states "remove gov. assembly" but it does not tell you HOW to do so, so I went to you tube and saw how these guys did it, to make a long story short , just use a small gear puller and the gov. pops right off , a small pressure ring under the bobbin holds the gov. in place . I then installed a used gov. assembly from another 20 hp motor, I used a gear puller to remove it from engine 2, and with a light tap from the hammer on the end of the bobbin, it snapped back into the original motor with no issues, I used RTV on the sump, and torqued the sump bolts to 200 in lbs. I then went thur the primary adjustments of the set up of the governor .
The next morning I set up the motor for a bench test , and the engine fired right up, I set the idle at 1200 RPMS, by closing the throttle valve against the idle screw, then holding the throttle lever against the idle screw, I bent the tang on the small (idle spring to 1700 RPMS) This is what the manual tells you to do !. Then I moved the throttle up to full throttle and it ran at 3400 RPM (Perfect).(You need to bend the tang on the BIG spring to change HIGH RPM settings and you need a good digital tach to do so ) I tested this several times and the new gov. assembly was doing its job.
So I have spent way to much time on the engine, but I have learned a lot , I have never seen governors blow up like this, but it seems to be the weak point in these engines.
If your not mechanical minded don't mess with the governor ! Let a pro adjust the gov. for you !
I hope this helps some one.

TY Jim

will you have proper crankcase end play using rtv rather than a gasket?

In case, adding to what was just posted... the crankcase end play 38 mentioned is the amount of end play the crankshaft has. The crank is supposed to be able to move a small amount inside the crankcase. Horizontal engines will have side to side motion, vertical engines will have allowed some up and down motion. The limits are set by the thickness of the crankcase(pan) gasket. B&S sells gaskets of differing thickness to adjust the end play. If too small, you'll have binding, and perhaps overheated bearings. If too loose, you may have noise or again, binding. Potentially, the connecting rod could get a little out of position on the throw as the crank moves from one limit to the other.
RTV will squeeze out, and allow the two halves of the engine block/pan to perhaps move too close together.
It might not hurt to check that you do have end play, and that it is not too much.
tom

It was RTV'd when I took it apart, and similar engines with bad governors were all RTV'd, no gaskets were present. I did have crankshaft end play , and the sump was torqued to 200 inch lbs, as stated in the manual . It fired right up and behaved nicely , NO RACING, and then I adjusted the low idle and high idle to specs, once installed on the DR brush hog it worked like a champ !

It just seems odd that the governor weights fly off the gov. assembly so easily ! B&S needs to build a better governor.

My 2 cents , Jim

From what I understand, the gear that engages to spin the governor is susceptible to getting brittle from being bathed in hot oil. When that happens, it can and does decide to shatter and leave bits and pieces scattered throughout the sump. Why? Just because.
Similar to the plastic cams and gears used in some engines. I think someone decided to save $.56 per engine... ok, maybe a buck or two, and let the future take care of itself. Kinda like a politician who gets a bridge built(his money? no.) but no buckos to pay for keeping it painted and rust free... let the future..
I wonder if installing a used governor might have been a bit short sighted as I would expect one to be partway through its life, and subject to coming apart sooner than a new replacement. I guess you will find out. As far as I know, there is no maintenance or other thing you can do to prolong the effective life of the governor. It's bathed in oil, or oil splash, whenever the engine is running, so lack of lube would be difficult to imagine. Only thing I can figure it heat embrittlement. (temp cycles .. cold hot cold hot)
tom

JimC_Vt said:

It was RTV'd when I took it apart, and similar engines with bad governors were all RTV'd, no gaskets were present. I did have crankshaft end play , and the sump was torqued to 200 inch lbs, as stated in the manual . It fired right up and behaved nicely , NO RACING, and then I adjusted the low idle and high idle to specs, once installed on the DR brush hog it worked like a champ !

It just seems odd that the governor weights fly off the gov. assembly so easily ! B&S needs to build a better governor.

My 2 cents , Jim

Click to expand...

If the other engines had rtv instead of a gasket...they had been apart before and NOT assembled correctly.
Don't get into a habit of using rtv on crankcases. You will get burned eventually.
They have somewhat precise (for mower engines) tolerances built in and need the gasket . You will end up to tight on a top bearing sometimes o much it won't even spin if you use rtv.

The governors are a weak link but usually only if the engine gets over-revved.
People setting it running or revving git up by hand grenade them.

Luckily they are only about 20 bucks and not too hard to replace but still an annoying job.
You shouldn't need a puller to remove . I just pull them up and out or pop out with a screwdriver.

Always static adjust a governor.

Push carb to full open throttle and see which way the arm moved.
Then loosen the gov arm screw and hold carb to full throttle while turning the gov shaft the same direction it moved when you pushed throttle to full.
Tighten clamp.