I got to ride RollingThunder's V-force last weekend and it has the Bartlett Airbox installed on it...it ran AWESOME! Throttle response and ability to lift the front end (at will) was everything I had dreamed my P650 would be one day (without the need for a BBK or nitros). I don't think the airbox mod was the only thing that made his V go so fast (he had other mods including dual Yoshi pipes, etc.)...but I'm guessing it was one of the key reasons.

Anyway, that V-force got me thinking that perhaps I should try to mod and/or open up the airbox on my 2002 P650 (which currenty has a BF650 airbox installed). I first thought about adding a 2nd snorkel to the right side front of the airbox...but then I thought about removing the lid instead. I know my old 2003 P650 ran like crap without the lid on...it idled ok, but bogged down horribly when I gave it gas b/c it probably needed to be rejetted for the extra air.

I never tried to rejet it to make it work with the lid off b/c I read on some atv forums that others who have tried to remove the lid on their P650/700 did not have good results (never could get it to run smoothly aftetr trying different jet sizes). The only plausible explanation I read was that the extra air turbulence screws up the motion of the carb slides (vacuum operated slides). While this makes some sense, I have to wonder why it is that most sport quads can run great with their airbox lid removed, but not the Kaw V-twin. Can it be that NONE of the sport quads who remove their lid have slide carbs like ours??? That seems a bit of stretch, but perhaps its true (I dunno).

***HERE'S MY IDEA.
I'm thinking about removing the airbox lid and covering the top with pantyhose or K&N outerwear material. Seems to me like this would offer a tad bit of splash protection while also smoothing out and slightly reducing the airflow coming in from the open airbox area. Has anyone tried this on their Prairie 650/700??? I would interested to know what their results would be.

***ANOTHER IDEA FOR MY SUPERTRAP IDSX MUFFLER
I have a full system Supertrapp IDSX with all 12 discs installed...I'm thinking about buying more discs and adding them to the muffler to allow more airflow at that point. Has anyone ever added more discs than the 12 that come with the pipe??? If so, did it make any noticeable difference in performance or sound?

So what do you guys think?

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

why not try and cut a hole in the lid and cover it with some nylon and see how that works.
you will get more air but not too much.
i think with the lid all the way off with just nylon it would still get too much air.

 

Great thread.
You actually saved me the time to write it as I just purches a 2005 BF 650 that is bone stock and I want to take the lid off and rejet for more power.
I have done this before with GREAT sucess on ;
2004 YFZ 450
2005 KFX400

I havnt taken my lid off but if taking it off will make it die or cut out when given full throttle, that just shows that it needs more fuel which is a good thing.
When I took the lid off on the YFZ AND the KFX, anything past 1/2 throttle it would fall on its face. Once I rejetteed, it was a totally different story - much more power.
I plan on keeping my fairly stock with very few mods like a Dyna (Or moose module), some airbox lid/mod, and possibly the muffler mod.

I hope that there are some people that can share there info as far as taking the lid off and how much they had to rejet and hopfully they were able to keep good manors with the quad.

Don
2005 BF 650
2001 Harley Road King
2001 F150
1992 Geo Metro (45 mpg- 52MPG with ACETONE)

 

There isnt a such thing as too much air- you simply add more fuel.

 

Open airboxes and mud/water don't mix real well. I know K&N makes air box lids w/ their filter material and outerware to replac stock lids. You can also try the uni-vents perhaps. All sport quads that I know of have slide carbs, as well as that v-force you rode I'm sure. Any way you go about it, you will need to rejet most likely to get the quad to run properly.

 

I dont plan on getting my brute down that deep in water. I just do trails/hills.
Good point though.

 

Scooter,
While most sport quads ( my Wolverine included) have similiar carbs, they are mechanical slides,moved by the throttle cable, some utility and sport/utility use a vacuum acutated slide for smoother response under load, the cable opens the carb, but the vacuum difference between the engine and the intake creates a pressure difference on a diaphram that raises/lowers the slide. If you remove too much of the restriction of the air box, it takes longer to build up the pressure difference, so the slide moves slower/less, and performance suffers. It is a fine line to get the air flow for better performance without creating carb problems. Unlike a standard carb, you can't just yank the airbox on a cv carb and rejet for more power, you need that pressure difference to make it all work. Lid mods are your best bet, keeping the airbox nearly intact will help keep the throttle response sharper while still letting you get some more performance.

 

Thanx for the explanation! I think you are right about the vacuum actuated slide carbs needing some backpressure to work properly...in fact, I just saw a thread on another forum which claimed that drilling twelve 1" holes in the lid was slightly more effective than using the Bartlett Airbox (which is an open airbox design used on the V-force). I have an extra lid, so I'm now thinking about maybe drilling twelve 1" holes in this lid and trying that with bigger jetting...if it don't work out well, I can always remove the lid altogether and see if that is better.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

I have ran my prairie with the lid off and with it modded. I currently run it with 9 one inch holes in the lid, decided to go with the lid on because I was a little worried about accidentally getting it wet although I don't ride in deep water or mud. Anyway I run 160&165 dynajet mains with the needles on the 3rd or 4th notch, can't remember which one. I can't tell much difference with the lid off compared to how I have it now. Also I have removed what I call the air dam, I am refering to the part of the airbox that is between the intake snorkel and filter it goes from the bottom of the airbox almost to the lid. It took a while to get the jetting lined out but it was a definite improvement. I recently had it at my local powersports shop and the guy who owns the shop says it runs better than any 4x4 he has ever ridden with the exception of 800 bbks. Also I saw an article in dirt wheels a few years back where they took a 650p and made it into a sand duner. Among other things they had the air box looking like someone had gone crazy with a drill, the reason for this story is just to let you know if you take the time to rejet propperly it will definately make a difference.

 

I just added a 2nd snorkel to my 700, I changed the main jets to 145/147.5, it feels like it's running very strong but I did not line it up with my buddys yet. I'm going to shim my needles a little,it does not stumble at all but I hear a very small amount of popping at low speeds. I also have the NAPA hose on the other side,DG5,exhaust mod and a 6deg key.