Honda - One of the biggest and the most popular manufacturers and producers of lawn mower Engines in the Market. They make engines for both riding mowers and push behind mowers. They have a massive repair/service network, which you can find via most dealers, and a great reputation...which has kept them around for so long.
Briggs & Stratton - have also been around a very long time and have maintained a great reputation for quality and productivity in the marketplace. They also have a great repair/service network, and are used by a lot of mower manufacturers needing parts for replacement or for new mowers. They make smaller lawn mower engines for push-behind mowers.
Kohler - also makes parts for smaller lawn mower engines. They are a very popular brand, for fuel-efficient, smooth running and quiet sounding engines. They also have a great support network for maintenance or replacements.
You can find much more about these, plus other brands by going online. Most lawnmower manufacturers tend to stick to the main brands because of their reputations, durability, and 'adaptability'.
This is great news for you because due to the sizes and shapes of the engines being of a standard design they are easier to get hold of if you need parts or even a full replacement. Whatever brand of lawnmower you have, 'well known or not' you can find an engine to fit it - to keep it running efficiently.
Some people do their own maintenance, cleaning or repair of their lawn mower engines at home, but if this is not your thing there are lots of companies out there who will do it for you. Again, you can find all the information you need online. However, if you do decide to 'do it yourself' there are online resources that offer you tips and advice.
It is essential that you check your engine regularly for possible glitches or replacements. A company that specialises in this will check all parts are running efficiently, ensuring your mower never breaks down or has any interior problems.
One of the main things to look for with lawn mower engines is what kind of fuel they are using and how they are started up - does it use a recoil cord or does it have an electric starter. With the electric option remember it will need a battery to keep it going.
The type of fuel used depends on the type of engine - is it diesel or gas? A Four-cycle engine will only need gas, whereas a two-cycle engine will need a gas and oil mixture. However, Four-cycle engines are considered to be more efficient needing less maintenance then the two-cycle engine.
With lawn mower engines do a bit of research into manufacturers, maintenance, parts - taking into account the make of mower you have and if it will fit. No matter what type you have you can find an engine or parts that will keep your lawnmower working as efficiently as it always has....