yes, i had a older snowblower that had no pipe, chain saws dont have a pipe, weed whippers dont have pipes, so small stuff but idk about 4 wheelers i guess
It would probably start but running/riding without an exhaust is just a bad idea. Your back pressure would be all messed up and the exhaust needs to be coming out with the wind never against it ! ( there's a very good reason why every type of exhaust system is facing/diverted backwards )
It would definitely run really weird and choppy ... And yes VERY LOUD ! I would think it should still start after a bunch of tries tho, hopefully the guy you bought it from isn't hiding another, potentially bigger problem by saying it won't start only because of the missing exhaust/downpipe ! ! !
Next I would check for spark, take the cap off of the cylinder/spark plug and hold it about 1/2 inch away from something metal. You should see a nice bluish current. Might sound stupid but I always check for spark on my blaster in the dark haha. That way there's no guessing or questioning ... If you have spark you will have no problem seeing it !
Good luck with everything, I'm hoppin off the site as I have to be up in 5 hours for work. Ill check back tomorrow to see if you've made any progress or found anything else out !