i have an 88 honda trx300, and the only problem i have with it is it has a slow return to idle. After you rev it or rolling along and have to change gears the rpm won't slow down enough. I can't seem to adjust it enough to fix it.

 

I would first check for a air leak. I have seen bad port jobs do this and a clogged up carb as well.

 

Yep that sounds like an air leak for sure. If it was a 2 stroke I would say crank seals, but since its a four stroke I cant say for sure. But I would suggest checking the rubber in-take boots they might be cracked and sucking in air.

 

I checked the rubber boot and its fine. Its still in good shape.

 

Try spraying some carb cleaner or starting fluid aroung the intake while its running, if it revs up when you spay a certain area, inspect there for air leaks.

 

This is also a sign that your pilot jet is too lean.

 

Great Idea... forgot about that little trick...be careful with the quick start (starting fluid) its pretty strong stuff and can do some damage if hte motor gets a good whif.