Engine #s could help. I don't know if this unit is the right age to have a carb with an accelerator pump on the side or not. I would remove the airfilter housing and reinstall the carb nuts. That way, you will have access to throttle linkage and such. MAy want to look down the carb throat and determine if the screws in the throttle plate are secure.

Thanks for the reply. I wish I had checked this earlier when it was still light outside. I will check the numbers tomorrow afternoon and post the information. I will also take a few pictures (pictures always help me). I do think it has some sort of accelerator pump as the fuel line goes into something right after it comes out of the fuel filter.

Engine # are as follows:
Model: CH20QS
Spec: 64556
Displ: 624
Serial: 2507515727

What do you mean by re-install the carb nuts? I did look down the carb and all looks good. I have tried to attach a picture of the engine with throttle linkage and I believe the accelerator pump.

Here is a link that might be useful: {{gwi:126892}}

On yours all you need to do is remove the entire airbox assy and you can run it easy enough to see a bit more to aid in troubleshooting. Yours won't have an accelerator pump. What you see is the fuel pump. Kohler does have sevice manuals online at no cost. When you change your fuel filter, "run" the line and catch some fuel in container so you can look for water and debris. Once that is done, run the line from the fuel pump into a container and crank the engine over to see if it is pumping a fair amount of fuel.

Here is a link that might be useful: Kohler

I have already drained the fuel and ensured the fuel is good. I also removed the airbox assembly and filter and ran the engine, I can see the fuel coming in as it runs. It runs fine and will throttle up a bit but just not what it should. Could it be a clogged jet?

Thanks for posting the link to the service manual. It will be a huge help. Will be looking at it again tomorrow late morning.

In a nut shell, if you can't manually use the throttle shaft and get full throttle- that would make one think that it is starving for fuel. So, if what I am hearing is that is what is happening- delve into the carb and give it a stern cleaning.

I never did make room in the garage and it is getting really cold and nasty outside now. This will have to wait a few days till the weather cooperates.

Ok, finally was able to look at this again today. I am able to throttle it up a bit more using the throttle linkage but still does not go up to where it should.
Cleaned the carb out pretty well and still no luck. My manual shows that my main jet has a solenoid. Could the solenoid not be functioning and causing it to not rev up? Getting pretty close to taking it to a pro.

Just an FYI- The problem was a bad ignition coil for the rear cylinder. $50 fix but lots of time wasted. Thanks for all the input though.