94 VMAX 600 Airbox Puzzle

[Hobie-Wan Kenobi]

I bought the sled used and the airbox looks odd. Standard OEM opening but, the open one is facing forward and the top one (OEM configuration) is closed (removable cover).

Why would the airbox be like this? A pro would be a ram-style effect when going faster I suppose. All part numbers have a sole opening on the top (pulling air from my the handlebars).

Has anyone found an airbox configuration that works better than stock for these engines?

Runs on the lean side on high end (one cylinder especially) and mid range seems good after plug chops so, adding more air probably wouldn't be beneficial. Low end and idle are "thin wet", as in not oily but, some fuel in there. I'm doing the pilot screw to fix that part.

Don't use the above info too much, as there are fuel/air tweaking I need to do with jetting and such.

 

[GG MM]

I'm in the same boat, trying to undo previous owners shenanigans. It's an epic battle, if only it was the last owners ridiculousness I may be able to get some insight...
I've read to not mess with the OEM airboxes.

 

[Hobie-Wan Kenobi]

I'm in the same boat, trying to undo previous owners shenanigans. It's an epic battle, if only it was the last owners ridiculousness I may be able to get some insight...
I've read to not mess with the OEM airboxes.

The previous one told me he recently did an "oil change" on it. Also gave me a jug of Yamaha 4-stroke oil and said "this is good stuff". Needless to say, I drained it and put in 2-stroke oil. Adjusted the cables and all that. Went from a smoke machine getting 4mpg up to about 10-11mpg now and way less smoke.

I know the guy and he isn't a crook. He bought it, riding it hurt his back so, he sold it in the matter of a month or so. No chance of getting an answer to why it was done. He didn't do any mods.

 

[Cherrypicker]

I bought the sled used and the airbox looks odd. Standard OEM opening but, the open one is facing forward and the top one (OEM configuration) is closed (removable cover).

Why would the airbox be like this? A pro would be a ram-style effect when going faster I suppose. All part numbers have a sole opening on the top (pulling air from my the handlebars).

Has anyone found an airbox configuration that works better than stock for these engines?

Runs on the lean side on high end (one cylinder especially) and mid range seems good after plug chops so, adding more air probably wouldn't be beneficial. Low end and idle are "thin wet", as in not oily but, some fuel in there. I'm doing the pilot screw to fix that part.

Don't use the above info too much, as there are fuel/air tweaking I need to do with jetting and such.

I have had a couple of these sleds, the top of the air box opening shouldn't have any kind of cover it fits into a plenum running from behind the windshield that should have a "coarse foam" filter the width the the open area, later models with trailing arms also have this. It will keep out the mice and bugs, but not snow powder, and the carbs are subject to freezing up some of the smaller openings in the carb throats. I suspect that is why Yamaha had carbs that were liquid heated. It wasn't totally a solution.