Hi guys,
i got a used small lawn mower last year. Since the previous owner had already tried to repair the mower, everything was no longer in its original condition. Engine model is Briggs Intek 825 (Engine No 122607-0210-E1) OHV.
Since it wouldn't start, I carried out the following repairs:
- new ignition coil because the old one was rusted - I would put the OG back on. Rust has zero to do with spark.
- Replaced crankcase breather
- Carburettor replaced because the old one was damaged (replica model, strangely enough it has a screw on the side that doesn't really change the mixture much). OEM or Chinese Amazon/Ebay?
- valve adjustment made which i believe is right as it starts good?
- new mower blade. Was it balanced prior to installing?
After these adjustments the mower starts easily and very quickly. There are no misfires or anything like that. I used it for the rest of the year but noticed more and more that something was wrong.
Yesterday I turned the mower on and wanted to mow and noticed that the symptoms had worsened. When I turn the blade on, it quickly starts to smoke slightly bluish and it seems as if there is no full power.
The blade engages normally, but when there is resistance when mowing, you notice how the engine is struggling. Do you have good compression, spark, air and fuel flow? There is also a "wroom" noise every few seconds that feels like the engine is shaking. Are the engine to deck bolts tight and present?
The motor also makes a rattling noise, Does it have oil in it? although I've seen in videos that this is probably not unusual. I then removed the spark plug and noticed that it had a black crust. Need to de-carbon the cylinder per yours and every other engine manual out there.
After I cleaned it, I turned the carburetor mixture screw while running the engine, but didn't notice much of a change. Could be an air screw. No change means that carb circuit if plugged. Leads to low power like you described. After a minute of running, the spark plug was crusted black again. Too rich (plugged air filter) and or sucking down too much oil. Sounds like she was wore out when you got it. People don't toss perfectly good mowers.
The oil level is exactly in the middle of the measuring scale so it is not overfilled. Needs to be AT THE FULL MARK all day every day. Unfortunately, I just don't know where to start. I don't have a compression gauge, but I was wondering whether it could be the cylinder head gasket. Go to your local auto parts store. They loan tools for free.
But does that also explain the lack of performance? Yes it does. Drinking oil, fouling plugs and a partially plugged carb, sounds about right. Maybe you can help me determine the next steps. Need to figure out where all the oil is going and why. Clean the carb.
Thanks in advance and greetings