To clean it first start with a cool engine. If your mower has a fuel valve switch it off. If you can disconnect the spark plug too. Next use a leaf blower to blast away any old dirt and major debris. Now gently lay the mower on its side fuel cap facing up. Try to get rid of any junk on the mowers underside as well.
The Sun Joe MJ104E has more than 1250 five-star reviews on Amazon. Buyer Jim has had his Mow Joe for more than a year and left it in the weather and abused it otherwise. He is happy with how it has performed. He cautions against buying the 16-gauge extension cord recommended by Amazon. Instead choose 12 gauge for 100 feet or more and 14 gauge for under 100 feet.
Your Best Digs rated the Greenworks 22502 as the best electric lawn mower. The reviewer found this push mower easy to maneuver thanks to its lightweight design. He also liked that it was much quieter than the gas mowers he tested. However he noted that dumping the clipping was awkward since there was a crossbar in the way and he would have preferred it if the mower came with an extension cord. Greenworks offers the option of buying the mower with an extension cord for $30 extra.