Does anybody know if the airbox in the HO is the same as the none HO. Greg Sims did a great post the other day about gains made by getting more air into the air box and ultimately improve breathing. What I am thinking is if the new airbox has a bigger inlet tube than the none HO then this could be the air flow improvement I am looking for. Any thoughts?

 

The air box is indeed different, but suffers from the same restriction. Just pop the lid and run it and you'll see.

Im still looking for a way to enlarge the tube and still use the stock location.

 

Air box cover and duct is the same on Sportsman 500's from "99" up including the HO. Look at the Magnum 500 cover. It has quite a bit larger intake. Your 98 has the old style air box. I converted my old "97" Xplorer 500 to the late box and after considerable carb tinkering (changinging all the parts as found in the late carbs) I found no apprecable difference. Not worth the trouble. Maybe at lower altitudes you would notice more change.

 

Someone, and I can't remember who it was (last week or the week before) put out some pictures of a yellow 500 HO with snorkels that he had put on his machine. The one was coming off the airbox off the right side of the machine. He used black ABS pipe for the snorkel. My question is, if you increase the air into the airbox, also keeping the original stock air line going to the air filter, do you then need to do any rejetting of the carburetor???

 

Since plastic hole plugs are available at most Ace Hardware stores... how about, drilling 1/2 holes in the airbox lid one at a time until the performance has peaked, then filling the unused holes.

By using the formula PIIR2 for the area of a circle, figure out the area of the combine holes and select an outlet, whether it is 1 3/8 or whatever and waterproof it and run the intake up above the potential water line.

Would this work? Any Thoughts?

 

Good thought Thor, on drilling holes until you find a happy medium with the air volume. I never thought this would make any difference, until I remembered a buddy who had flipped the air filter cover on his 350 Chevy for a little more breathing space. I don't know a dag-nabbed thing about carburetors and jetting, I leave that up to someone who has carburetion time, not just riding time.

 

tcdal0, to answer your question yes you will need to re-jet. This is why this type of work is tedious cos every time you increase the airflow it must be jetted accordingly. Otherwise the full potential may never be reached.
As for the intake tube this is what I plan to do. Remove the old intake tube and take it to my local auto parts store and try to match it up with a radiator hose. There are many different configurations and sizes so I am hoping to find one with similar bends and somewhat larger in diameter. What do you think?
swac1, drilling holes in the airbox cover is not a bad idea (another alternative is to make a cardboard replacement for the experiments) but as I mentioned earlier the carb must be re-jetted each time you increase the airflow.

 

Hmmm, could have sworn they were different. Maybe I looked at a 98.

Mine screws to the lid with 4 screws, and is rectangular shaped.

Thought Gregs pics showed a different style OEM too???