B&S 10L802-0858-F1 Run Issue (Auto-choke/Govenor?)

[nsnd]

First time poster, but I found your community while trying to fix a 10-year old Craftsman mower with a Briggs and Stratton 10L802-0858-F1 motor. For the past 2 years, it was used by renters, but I have since moved back to my home and started using it again. At first it didn't start, but I changed the sparkplug to an E3 Spark Plug E3.10 in September of 2020 and it's been running ever since.

Then my new problem started in February of 2021 when the mower constantly surged while mowing the lawn and puffed out black smoke from the exhaust. After some research, I came to the conclusion that I've been neglecting thing old thing and the the diaphragm was probably worn, since it had never been changed.

I ordered a replacement diaphragm and gasket directly from B&S (part# 795478) and used some carb cleaner to clean everything up. I also took this time to drain the oil and fill it back up. Once it was all put back together, same issue. I checked the E3 sparkplug and found carbon fouling (dry black fuzzy dust particles), which I understand to mean the engine has been running rich (hence the black smoke during the surging).

I did more research and found that Lowes sold the same diaphragm kit with the addition of the spring and main jet filter. Since I hadn't replaced the spring, I figured it was a good option to try. I ordered a new diaphragm kit (5083D), sparkplug (5435K), air filter (5088H), and primer bulb (5085H). Tore everything apart again and put it back together.

It took a couple tear downs after the Lowes trip to get it running, but now it's firing up and running..... somewhat. It's not surging like it was, but seems to rev up for a few moments, then die out for a few, then rev back up. Eventually the motor dies when I have the air filter on. Here's a video to help explain this:

.

When I initially took the carburetor off the engine, I had trouble disconnecting the auto-choke/governor linkage and thought I bent it. So before I order more parts and tear apart the motor any more, I thought I'd check here for more expertise on my problem.

Any help will be greatly appreciated.

 

[Rivets]

A couple of things I would be checking, first I hate the E plugs and would install a Champion J19LM plug. Second, check to see if you installed the carb diaphragm and gasket the correct way. The diaphragm goes against the tank and the gasket against the carb. Third, to me it sounds like it is running to fast, you need an experienced ear or tachometer to set properly. This manual may be of some help. https://drive.google.com/file/d/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00/view

 

[nsnd]

A couple of things I would be checking, first I hate the E plugs and would install a Champion J19LM plug. Second, check to see if you installed the carb diaphragm and gasket the correct way. The diaphragm goes against the tank and the gasket against the carb. Third, to me it sounds like it is running to fast, you need an experienced ear or tachometer to set properly. This manual may be of some help. https://drive.google.com/file/d/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00/view

Thanks for the reply and the manual! I confirmed the diaphragm was installed on tank and the gasket on top (against the carb). I'll see if I can get my hands on a tach and refer to the manual you attached.

 

[nsnd]

I purchased a tachometer and hooked it up. It appears the engine is running fast. When I check Table 1 (Section 5, pg. 28) for a 21" inch lawn mower blade, I should be running 3,250 RPMs. However, I'm getting a much higher number on my tachometer, generally from 5,500 to 6,000 RPMs before it starts running rough and dies.

If I'm reading the documentation correctly, I have a Pulsa-Prime carburetor (Section 3, pg.4: Fig. A; and Section 3, pg. 7), and it doesn't appear to be any adjustments on the governor. Since, linkage and spring are worn, I'm going to order new parts to ensure those are working properly.

 

[Richard320]

I purchased a tachometer and hooked it up. It appears the engine is running fast. When I check Table 1 (Section 5, pg. 28) for a 21" inch lawn mower blade, I should be running 3,250 RPMs. However, I'm getting a much higher number on my tachometer, generally from 5,500 to 6,000 RPMs before it starts running rough and dies.

If I'm reading the documentation correctly, I have a Pulsa-Prime carburetor (Section 3, pg.4: Fig. A; and Section 3, pg. 7), and it doesn't appear to be any adjustments on the governor. Since, linkage and spring are worn, I'm going to order new parts to ensure those are working properly.

You might want to doublecheck that. Remember, you get a spark every revolution, whereas a lot of engines (automotive) only get a spark every other. The tach may be reading double.

 

[ILENGINE]

Which models of those style carb has issues with the fuel jet in the emulsion tube coming loose and falling out. Tried to find the bulletin but no luck.

 

[nsnd]

You might want to doublecheck that. Remember, you get a spark every revolution, whereas a lot of engines (automotive) only get a spark every other. The tach may be reading double.

That was the callout on the tach I bought. I have the tach set for a single cylinder-four stroke engine, but that could still be an issue I need to address. I felt that when I initially took my carb off, I may have bent the governor linkage and have since tried to reset it. Not only that, but the governor spring might have also been damaged. I also noticed that when the engine is cold (I live near San Francisco, so about 50-60 degree F outside; near sea level), and I try to start it, the choke is wide open. While the engine warms, the choke closes, sputters, and re-opens. Then the process starts all over again. Correct me if I'm wrong, but the choke should start closed, then open as the engine heats. I've searched high an low, but I haven't been able to find much information on my carb/governor setup to reference.

Which models of those style carb has issues with the fuel jet in the emulsion tube coming loose and falling out. Tried to find the bulletin but no luck.

I hope not my style. There isn't much to the carb, but I haven't seen much on it indicating that could be an issue.

 

[nsnd]

Received the new governor spring (B&S 698719) and linkage (B&S 698835) and installed them. I definitely mutated the linkage and the spring was also worn (see image below). Now I'm have trouble getting the mower to even start. I poured few drops of gas in the carb, and it will fire right up, but immediately dies.

One things that's been bugging me is the primer bulb I installed. Come to find out, it was a dry primer bulb (694395; 219706 from Lowe's) instead of the wet primer bulb (694394) that I removed originally. So before I go any further, I'm ordering the correct primer bulb, and I'll replace that bad boy again.

Learning experience :-D.

 

[Bellcrank]

On this model the air filter clogs often causing the spark plug to foul. If you do not do a complete carb cleaning (Take'n every removable part off the carb and cleaning ) just buy a new carb. This video shows how NOT to clean your carb :

. This video shows how to clean your carb correctly :

.

 

[nsnd]

Bellcrank, Thank you for those videos. I believe I saw the first one (don't), but never watched the second one (do), at least not in it's entirety. Other videos referenced cleaning the main jet, but I never saw how they removed it. After watching that video, I was able to check that, while I tore apart the carb to clean and install the new primer bulb.

Lawn mower is running again, but rough with black smoke. I ordered a new Champion J19LM spark plug. Hopefully, that will be my last purchase :-D.