Looking around it seems you allow non-("cars, trucks, and motorcycles") motor vehicle questions. But what about other mechanic problems that are related to non-vehicles?
For example lawn mowers, weed whackers, farm equipment, things pulled by/powered by tractors, motorized equipment. Things you would take to a mechanic, things made out of the same sort of parts, but not designed to transport people?
If not, does that sort of stack exchange community exist?
In the past these types of questions have been allowed. For instance:
Lawn tractor, difficulty starting in cold weather
Can an ignition coil melt-down?
Craftsman push mower won't start after hitting stump
Is it OK to run a trimmer without the plate-filter support?
( Also look under the small-engine tag.)
From my point of view, these questions are very much on-topic for the site. I think the delineation is whether it is about or has to do with the maintenance of something motorized, not just conveyance.
As far as I know, there isn't another Stack like this one which covers anything to do with any type of motorized anything, mechanics or otherwise. There have been several proposals, but I don't believe anything has held on until Beta as of yet. I'm not saying they wouldn't make it as their own Stack, just that they haven't gotten that far in the process before.
Please remember, this is me the person talking, not me the moderator. If the community at large says otherwise, this position could be changed.
Hope this helps.
It looks like you have lots of room here for your questions, so I'm happy for you!
If you want another option for your small engine lawn equipment questions, I recommend checking out Gardening and Landscaping. It's a relatively small part of their content, but much of what you seek is on-topic, and new questions are always welcome!
Search some tags, including, lawn-mower, string-trimmer, tools, tool-maintenance, small-engine, repair, chainsaw, to get an idea of what's on-topic and see if you find anything you'd prefer to ask over there.
There may already be questions related to what you have in mind. Don't be surprised if you see great answers written by people from here, including Paulster2 himself!
Since they don't cover large scale agriculture, there aren't many farm equipment questions, but they're welcome in the context of home-gardening and lawn maintenance. However, a "tractor" search here brings up 74 results (as of this writing), so this looks like a perfect place.
I'm always anxious about posting a question where I'm not sure it fits the scope, but everyone here is really nice and won't make you feel bad if it happens! Asking here on meta was smart, but if you're still not sure, don't hesitate to go into their chat room and ask around. You'll be welcomed right away. (Gardening also has a great chat room.)
As Paulster2 said, there have been several proposals which might interest you, none of which have made it to the Beta stage. Agriculture and Farming is current, so you might want to post your tractor questions there as examples.
