"650 V Stars "Custom, Classic & Dragstar"
Ram Air Kit
Thanks to Benny Bryant
The inventor of the RAK
I kicked around the idea of using 2 separate K&N's (a.k.a. the Bak / Gak ) but finally 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.
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Not meant to replace the otherwise fine BAK or GAK but just a low cost alternative for comparable 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, modifying 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:
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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 equivalent 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 air box 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 tuning 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 air box. It acts as a relief valve for the excessive air being rammed in at high speeds. Plugging this will result in the carbs receiving 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 equivalent to the more pricey modifications but as Fox Mulder would say "Bring it on . . . !!" >Big grin<
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UPDATED INFORMATION
The original text of the RAK has been presented,
because it is one of the first air intake mods to successfully work. The RAK
works with stock exhaust, modified stock exhaust and after market exhaust.
Thanks to Benny ….all of his testing and development of the RAK….and it is
almost free and does perform very well.
As time moves on….updated changes and different procedures improve the
original instructions and help the individuals considering the RAK.
Most important procedure, is to follow the instructions, the air filter housing modification and hole sizes must be done properly. This will allow proper air flow will allow for easier diagnosis if a possible problem may occur.
As we read through the original instructions, mention of a KN air filter is an available option. KN makes a good product, increases air flow and can be cleaned and reused. In my personal opinion the cost of the KN air filter does not equal the performance gain for the money invested. There is a slight performance gain and the filter will last forever when properly maintained…..choice is yours to make.
Next …..the discussion of the “T”, that is stamped on the needle. Well, the “T” started to move around and is not consistently marked on the needles. When this problem started….doesn’t matter. The cure is the installation of shims. Two # 4 shims are very close to being the same as the 4th notch in aftermarket needles. These shims are available from Ziv, who makes an excellent stainless steel carb screw replacement kit or from your local Radio Shack.
The main jet modification….drilling the stock jets. It is now easier to find properly sized Mikuni main jets. Aftermarket catalog suppliers, Yamaha dealers and Ziv have Mikuni main jets available. Also note that the jet sizes referred to by Benny are DynaJet sizes, not Mikunis. The jetting chart on the 650CCND page references Mikuni jets.
There are instructions listed on the “CCD webpage” for the GAK and HC….both of these articles have excellent pictures and instructions…this extra information will be of great value when you get your hands on your carburetors. Different exhaust systems…..from stock to free flowing after market will respond to the RAK. This is the only air kit that will work with stock exhaust and free flowing aftermarket exhaust. Anyone considering exhaust changes should consider the RAK. The 650 vstar is lean from the factory….most exhaust mods or replacements will require jetting changes….you will be doing the same amount of work….only adding about 15 minutes to modify the air filter housing.
I hope this updated info and the presentation of the original RAK instructions will make your performance juices start to flow…..please post any questions or needed clarifications to the amended updates so that corrections can be made.
Thanks, MGD
