Hello:

I just installed a Two Bros exhaust and everything seems to be running fine. I live at 5,600 ft ASL so I think the exhaust made things just right. I am still nursing the bike though as it is new and haven't really gone above 6,000 rpm.

I have seen a lot of talk on this forum about disengaging the intake flapper when installing a new exhaust. Is this always true?

I do know on my other bikes you usually opened up both ends at the same time or atleast instlalled a KN filter. But they were all Italian V-Twins and came to the US severely restricted anyhow.

Please advise.

 

The intake flapper is a joke. As it turns out it was installed to reduce noise levels at low RPM's. At idle the bike is breathing through 2 very small holes. As the RPM's increases the flapper opens up and is fully open at or around 6000 RPMS this is where most people report a noticable increase in power. Thats because it is finally breathing like it should. The disabling of the flapper is simple. Removal is a bit more difficult.

Here is a link from Rogue Racing on how to disable or remove your flapper.

http://www.rogueracing.org/flap.htm


Hope this helps.

Mike
CTSmoto
http://cts.theallureimage.com/

 

i just got a custom map made, and it still has a spot at 3500-4000 rpm's that it seams rich. if i take off the flapper will i have to get it remapped again?

 

Removing the flapper or just disabling it will probably do the trick. Although with a custom map they should've been able to remove the richness at any rpm.

 

Well, I removed the vaccum hose today just to see what it was all about. As far as sound goes, I dont know if its any louder but it is... different. Did not see any performance gain. I will leave it off for a while just for the hell of it.

 

I didn't notice any difference in sound with the flapper disabled. Performance only increased when moderately accelerating -- full power take offs were not affected. Some day when I've got the plastics off for some other reason I'll go ahead and remove all the hoses and crap but it's just not enough weight savings to make it a Saturday job all by itself. Especially when the weather is so nice[8D]

 

it will take all of 15 minutes to remove every bit of the flapper and its componets.

 

Will it cause any problems with more water getting in the air intake during rainy days? Bearing in mind that i live in the uk and get alot of rain.

 

If you perform the flapper mod I recommend that you get a BMC filter street filter. I did notice that after I installed the filter that the bike responds better. If you have an aftermarket muffler like I have it is trying to exhaust as much air as it can. If the bike does not intake air to match the exhaust it does not run right. Someone also told me that after every mod to disconnect the battery for thirty minutes to reset the bike computer. This will make the bike relearn how you operate the bike with the new equipment. Hope this helps.

 

Shouldn't ... the flapper opens anyway. You're just making it stay open at lower rpms for better low/mid power. And I don't know nothing bout the computer on the bike learning how I ride[8D] That's a new one on me.