Engine is 12S907-1411-B1. The carb is 796608 and is OEM. Even has the B&S logo. I'm really leaning towards the governor spring. Mine doesn't look as heavy as the picture of the OEM one and if I just hold half of the coils it stops surging. bending the bracket to change tension doesn't help. As I stated earlier, the spring was missing when I bought the mower and I never could get it running right. Since the OEM spring is cheap, I'm going to try it anyway.
12S907 surging
- Thread starter kh0432
- Start date
I just reread the entire thread and noticed something I missed earlier. If I read right you are trying to install a mower engine on a pressure washer. As I stated earlier these run under different loads and may need different carbs. Engines on pressure washers run at a heavier load and require more low end torque because you are dealing with water pressure, not blades of grass. On top f that if the mower engine was on a WeedEater mower, it is most likely the cheapest engine out there. That spring you are talking about (governor spring) may not be the same on both engines.
The Weed Eater One was a little rear engine riding mower. I would think that turning a blade and being a rider would be a heavier load than a pressure washer pump. My other pressure washer has a smaller motor than this. What has me stumped is the fact that it will run fine under a load for the first 5 minutes before starting to surge. This wouldn't be the first time that I put money into a project only to wind up scraping it.
Three things cause surging on today’s small engines, rich mixture, lean mixture and improper governor setting. Wish I was standing next to you to see what’s happening. Only have two more things I can suggest sitting here. One, adjust the governor, you want to set the governed top speed according to the tag on the washer. I’ve attached a manual for instructions. Two, next time it starts surging take a can of carb cleaner and spray around the gaskets between the carb and engine block, looking for an air leak after the parts heat up. https://docs.google.com/open?id=0B6NaqjIxWV1ybEN0LWo3azl6OUU
Thanks Rivets, I actually have that manual. There is only one governor spring and doesn't have multiple holes for adjusting. If I increase spring tension rpm will increase and will decrease if I decrease tension but the surging doesn't stop. I'm still leaning towards a stiffer spring.
Well even though the new OEM spring was a little shorter than the one I had, I didn't cure the problem. It still takes about 5 minutes for the surging to start but now I just noticed if I place my hand in front of the carburetor I can feel air and a gas mist blowing out. I've adjusteed the valves. Should I pull the head and check the valve seats? Checked the compression and it's only 45 psi
This motor uses a Ready Start carburetor. There is no idle speed, it runs at high speed as soon as it's started. The only adjustment for the governor is to change the spring tension by bending the tab on the bracket. Since it has to get up to temperature before it starts surging is it possible that as the intake valve expands I'm losing my valve clearance. I don't think I should feel anything blowing out of the carburetor while its running.
You can adjust the governor and the high speed, if you take the time to read the manual. The governor arm may have moved on the governor shaft and the high speed is adjusted by changing spring tension. The carb jets correspond with governored top speed and if it is set too high, surging can occur. Need a tach to adjust properly.
PTmowerMech
Lawn Addict
- Joined
- Apr 16, 2018
- Threads
- 396
- Messages
- 3,018
If you only have 45lbs of compression, seems that it would be hard for the engine to keep up with itself.
If you haven't already, after it runs a while, kill it and check the oil fill tube for smoke. That's usually a good sign of a bad head gasket. I think I understood you right, when you said you could feel air and gas blowing back out of your carb. IIRC, that's another sign of a bad head gasket or PVC valve is bad.