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Join Date: Nov 2007
Location: Chandler, Arizona
I've never been a fan of this mod, mostly because those who do it use K&N screens instead of real air filters. But it also requires a lot of tuning to get right, and will never work perfectly at all rpms like the stock system. You have 3 problems. No filters, causing increased intake air flow, which leans out the air/fuel mixture, part of the exhaust removed, creating a loss of back pressure, further leaning out the air/fuel mixture, and you have the PAIR system still hooked up. You need to completely remove and **** can that whole system. Remove the hoses at the heads and cap where the hoses went. Remove the valve behind the gas tank that those hoses connect to, and remove the vacuum hose from the rear carb and plug the fitting on the carb. Since you no longer have a stock airbox, what did you do with the hose that went from the 3 way valve under the seat to the airbox? If you have a CA model, all the evap crap needs to be removed as well.
I would use UNI foam air filters with some kind of oil on them instead of the mesh screen type. They not only work a lot better at filtering the dirt out, but they don't lean out the air/fuel mixture as much. Also I would put some kind of baffle in the exhaust system to increase back pressure a bit. I have seen people use eye bolts in the exhaust to do that. If there is anything bad about carburetors, it's that they have a limited tuning range. With no filters and open pipes, you will never be able to tune the carburetors to work properly at all rpms. It will be too rich at some speeds, to lean at others, and just right through a fairly narrow rpm range.
Harley riders that run straight pipes hated EFI when it first came out. But then they discovered it could be tuned to provide a perfect mixture at all engine speeds, and they could run open pipes without destroying their engines. Apparently loud pipes were more important than keeping their bikes electronics free.
Kawasaki put a lot of work into designing the stock intake and exhaust systems, mine always worked perfectly idle to redline. It seems most people remove them just for looks. I personally love the '80s Japanese look of the Vulcan 750. And stock it is faster than a stock Honda Shadow 1100 Spirit.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike