Briggs & Stratton Opposed Twin Seems to Have Slow Governor Response...

[TylerFrankel1]

Hey everyone! I have a quick question I wanted to get some opinions on, regarding an old opposed twin cylinder Briggs. I rebuilt it earlier this year after finding it discarded with the cylinder heads off. I tore it all the way down, cleaned everything, honed cylinders, re-ringed and re-sealed, and it runs nicely. I replaced a boring Intek single-cylinder on my old beater Troy-Bilt lawn tractor with this nice, loping-idle twin, (just for fun). After tuning the carburetor it's done a great job with all the yards I've been cutting (8 clients or so, weekly and bi-weekly) and burns very little if any oil so far. Only real quirk with it I can think of is that the governor seems to have a crappy response time. That is, if I introduce a new heavy load in a sudden fashion, there is a noticeable 1 to 2 seconds decrease in the RPMs until the governor catches up and the RPMs come back. If I stomp the vari-drive pedal, the RPMs go from like 3200 to 2800 and come back over a couple seconds. If I lower the throttle down from full RPMs quickly, it will make you think it's going to shut off instead of idle, and then at the last second rev back up to idle speed. Nothing that makes me concerned or makes it less usable, but definitely slower than the single cylinder. I've checked, and the linkaes aren't binding or anything. I honestly expected the RPMs to be more consistent with this motor than my Intek because the flywheel is so big, it should keep more momentum. Is that normal for these old engines, or is something off? (Maybe carburetor? I got away with cleaning the old one ultrasonically but it was in rough shape.) Just curious. Thanks!

 

[TylerFrankel1]

After cutting a couple of yards since posting this I've started noticing a lack of power when heavy loads are put on the mower, after about 15 minutes of running. It gets worse and worse as the mower runs for longer. For curiosity I choked the engine and that brought power and RPMs up. I don't think I have a governor problem, I think I have a fuel system restriction. Either the main jet is dirty, the fuel pump is weak, my fuel lines/filter are plugged, or my tank vent might be bad. I'll investigate. Maybe time for an aftermarket carburetor and better fuel lines (right now its got some cheap Chinese line I bulk ordered off Amazon, I.D. may be a bit too small for 18HP). I checked compression on both cylinders and get 120 PSI both cylinders cold, which is excellent for a flathead motor afaik. Pretty sure thats ~8:1 compression which is about what they would have had new. When I did my re-ring/hone and re-seal this winter I checked valves and they were all within spec and sealing well. Not much oil burning to speak of either. So not thinking my power loss is from internal issues. Anyway just wanted to update the thread.