Vanguard 18 hp
 

I have a vanguard 18 and when it warms up the RPM's are all over the map? Where would you suggest to start with this? Any help would be appreciated! Thank you:beerchug:

I guess I'd start with a binding governor and governor adjustments

Did the problem start suddenly or gradually? Does it actually over rev? Does the speed seems to be normal and predictable while the engine is still cold? If it is simply surging up and down, and not necessarily over-revving, sounds like a lean mixture on the carburetor. Try giving it a little choke and see if that smooths it out. If that is the case, I would check fuel supply and probably suggest that the carburetor needs a good cleaning. It could also be a governor shaft and/or linkage binding, but generally that makes it go way over top governed speed, as Don suggested.

Thank you
 

I just acquired this tractor so what is normal I'm not sure yet. I got a chance to run it more today and I think it is just a sensitive governor. With the deck full of heavy grass it runs as smooth as can be it is when it's not working it's butt off that it likes to wonder the map! Thank you for your replies!:beerchug:

In that case, you are probably looking at a carburetor issue. I think that if you pull the choke just slightly, that will smooth it out. Those carbs are non-adjustable, so everything in that carburetor has to be just so in order for it to run properly. A casual observation inside the carb will probably tell you that everything is OK. However on more careful observation, you will find that there is a varnish build up particularly in the area of the emulsion tube and the main jet. That must be clean. If you find a white almost powdery film in there, that is evidence that ethanol has begun to take its toll on the carb. A proper cleaning will probably get you back in shape. Also, a little looseness in the governor linkage can cause some of the same symptoms. Feel free to ask if you have more questions.

Thanks
 

That could easily be the case. I picked the tractor up for free and it had been standing for quiet a while so that is very believable. Thanks for the answers!:beerchug: