R.A.K. - The Ram Air Kit
by: Benny Bryant

I kicked around the idea of using 2 seperate K&N's (a.k.a. the Bak / Gak ) but finially decided I would rather use a K&N replacement for the stock filter. Reason being, I think I would end up keeping the filter cleaned more often if I didn't have to remove my tank and risk the paint to get to it. With this in mind I gave some thought into the amount of air restriction the stock system would impose and how to eliminate it. I think the air ductwork FROM the filter to the carbs can flow as much if not more than the otherwise stock engine can pull. The restriction seems to be INSIDE the canister, from the outside air into the filter. It has but one small inlet hole on one side of the filter. To improve the air intake, Porky and I decided that a slot cut directly in front of this inlet ( 1 1/4" X 2 1/4" ) along with two other 1" inlet holes inside the chamber would do the trick. Kinda Tombugg style but still using the stock airbox for the filtering system.

RAK Intake

Not meant to replace the otherwise fine BAK or GAK but just a low cost alternative for compareable power. If you already have free flowing pipes and a jet kit , This will only cost you time. Works great with the factory air filter and even better with the K&N replacement filter.

Don't have a jet kit??? Well then, modifing the factory jets and needles will work too. Just takes a bit more time.

Leary of taking this project on ? I suggest the article in the ISRA Starcruzier on the "GAK" by Mark Jelic. It is the Best instructions for carb jetting that I have seen anywhere. Complete with pictures of everything you'll need to get the job completed fast and correctly. I would only add that you place a screwdriver on the factory carb screws and tap lightly with a hammer before ever trying to loosen them. They are Brass and will strip very easily if you try to remove before doing this.

Advantages:

• All together it is barely noticeable, maintaing the stock appearance.
• You don't have to take the tank off to clean filter.
• The filter gets colder air as opposed to hot air under the tank.
• No oily blowback on top of engine from the crankcase vent tube.
• No loud "Sucking" sound from under the tank.
• Roughly a "FREE" mod.

Required Parts

Our needles used the #4 slot of the cobra jet kit and a 1.2mm drill bit to drill out the factory jets to make a 120 jet. (use 125 / 130 jets with a K&N replacement filter) The K&N does make a difference at high speeds (especially above 65 MPH). Cutting a new groove across the top line of the letter "T" inscribed on the stock needles is equivilent to #4 more or less on the Cobra kit . You can shim to make finer adjustments. TonyO at Yamaha Sportscenter in Texas suggest using small washers cut from Coke cans for shims and Dadbenny uses o-rings. My kind of engineering >G<

Below are pics of the modified airbox with the stock filter. Jet and needle settings may change slightly according to the part of the country you ride in but the basics are the same. Also pics of the required parts to modify the stock jets/needles. Just place needle in a dremel tool etc . . . and use a thin dremel tool cutoff wheel to cut two or more additional slots into the needle under the factory slot. Drill out the factory jets with the correct size bit for your application and that's it. Just a bit of fine tunning from there. The standard setting for the mixture screws is 3 1/2 turns out. This seems to work fine with this setup as well .

I have a stock 650 and a RAK'ed one and the difference is significant. Definitely is Equal to the Baron Big Air Kit (on the 650) with 47-51 MPG riding two up with tall windshield and deflectors. (It just doesn't have to have the throttle as wide open to maintain a given speed, hence the better mileage)

Final note :

Leave the factory hole for air in the rear of the airbox. It acts as a relief valve for the excessive air being rammed in at high speeds. Plugging this will result in the carbs recieving too much air under pressure at speeds above 65 MPH. Also relieves excessive pressure when riding in Gusting headwinds.

We realize that it will take an actual run at Hot Springs to convince some folks that this Free mod is equivilant to the more pricey modifications but as Fox Mulder would say "Bring it on . . . !!" >Big grin<

New Needle Groove

Aircleaner w/o Filter

Aircleaner w/ Filter

Mod. Backing Plate