The regulator could affect the top end sure....but its not going to affect it 1000rpm. If its that far off its not going to run well from amixture point of view.

Valve clearances same deal...they will affect top end but not 1000rpm...Maybe 200-400rpm tops unless it really realy bad.

While you are at it stick a new plug in it.

try another gallon fo fuel too.

If the engine has lots and lots of time on it....you should really have a look at many things. Running the engine too long with worn parts can cause a failure. Then its too expensive to fix it. Example. Con rod could be worn. Maybe its a bearing issue, maybe you have a bent valve stem. Any of these problems that get continued use will shed metal into the engine. If you don't know what you are looking for its best to send the engine to someone that does.

Example. I had a con rod get a little sloppy on the crank pin. I figured it would be good for another couple weeks while I was waiting for the $30 part. I continued to run the engine even though I had another sitting there in the box. Well the rod failed, it got pushed through the side of the case, destroyed the sleeve, case, crank, of course it needed new bearings now and a new seals all around, the metal shavings damaged the head, and backplate rotor assemble. SO what was a 30min fix for about $30 turned out to be a engine that never flew again. I tossed into the scrap heap for spare parts not there were many. By the way the engine had 4 years of flights on that connecting rod. I have no idea how many flights but it was up there.

Troy