hornet 250 flapper mod

**phyx1u5** · 8th September 2007, 19:59

for more info on what this is go to: http://www.919.org/flap.htm
I came across this purely by accident. I was doing a twin headlight conversion on my hornet and i had to pull the tank back to hide the excess wiring underneath the tank. Unbeknownst to me i accidentally disconnected the vacuum pipe by pulling the tank up too far

After repeated failed attempts to start and idle the bike i adjusted my carb to idle at a higher rpm this was all good for a while but i still wanted to know the root of the problem. Anyways after fiddling for a while i finally (accidentally) put my finger over the vacuum hose and the bike began to idle smoothly (thnx to MSTRS for the heads up). Because of the awkward position i cbf'd reconnecting the pipe properly so i just plugged the end with a small screw. Bike now runs fine.
Anyways if anyone with a 250 hornet wants to try this out the pipe is located behind the fuel switch, pull it out and plug it with something. make sure its not the fuel pipe ur pulling out! cause thats not really a good thing

This mod is supposed to make power curve more linear at lower revs, though how valid this is for a 250 hornet i have no idea. try it for yourself n see.

**gijoe1313** · 8th September 2007, 22:17

Good stuff! Always glad to hear of more Hornet riders out there doing the bizzo on their pride and joy!

Hmmm, my bike runs plenty fine, guess I'll do the old thing and leave well enough alone! (If it ain't broke, don't fix it!

)

Will be interested in your twin light look, my little ol'Hornet has that configuration and looks good with it...piccies please! And yes, excess wiring is a biatch, Jeaves and I were looking at the spaghetti at the front of my ride and working on streamlining it...sigh...

Gotta luv the little ol'Hornet though!

**delusionz** · 9th September 2007, 02:53

is the vacuum hose the one that connects from the crank case to the air filter element? is it safe to plug this up is it? i thought it had to be sucked through for a reason? -- thats what made me decide against ditching my air box for pod filters

**phyx1u5** · 9th September 2007, 09:15

hey gijoe ive put up pics on the show us ur 250 page Click Me

Delusionz, supposedly, and this is just what ive got from reading the 919.org page, "This is a flapper door actuated at certain rpms that cuts off the the majority of the air flow to the airbox!...this was done by Honda for no other reason than to keep the noise down for EPA testing!...[After disconnecting and plugging the hose] the bike no longer has a surge of power at 5500 rpm, but it is not because you are losing horsepower it's because it is making the power curve more linear & producing better power below 5500 rpm so when the power picks up at 5500 rpm you no longer feel it as an increase since the power flows much more smoothly now."
Once again i dont know how valid this is for a 250 as i havent gone out riding since i plugged the hose yet, will go for a ride later today and update.

**obstacle** · 9th September 2007, 10:32

Originally Posted by phyx1u5

hey gijoe ive put up pics on the show us ur 250 page Click Me

woah! it's like a time warp! your link goes right back to this post!

I'd be interested to know if this works on the 250 though. Having only ridden mine for an hour or so i'm quite surprised at the power surges as it hits different rev ranges, it'd be nice to free that up a bit and get the same power across the board.

**phyx1u5** · 9th September 2007, 10:42

haha oops fixed teh link now.
still havent had a chance to go out as its raining now and i just washed the bike!

dun really wanna get it wet....yet.

**phyx1u5** · 9th September 2007, 10:50

heres a pic of the flapper mod done on my bike.
soz for bad image quality coz i did it in the garage with a torch and phone in the same hand :S
You can sorta make out the pipe with the screw plugging it.