I heard about this in another post. What exactly is this all about. Im all for the free HP Mods! You have to excuse my ignorace, Im pretty much a text book Noob!

Thanks!

rc51.org will explain it all.

Ya i guess... I was hoping to get an answer here. Im not paying to use any site!

To do the flapper mod look right in front of your gas tank and right below your instrument cluster. There will be a thing there that looks like a mushroom head with a tube coming out of the left side of it. Its the valve that open and closes the flapper. Pull that tube off and plug it up with a screw or something. It will just sit off to the side so dont worry about it. There you go. You just did the flapper mod.

The soft rev mod is alittle tougher cause you have to move around some wires on your ecu. All it does is remove the soft rev so you can run it up past 10K with out it hitting the rev limiter. I personally haven't done this mod cause I feel better with the rev limiter there cause I spent alot of money on my bike and I don't want to blow it up.

haha, I hear that. I will have a peak at that tonight.

If you remove the flapper actuator (on top of the air duct), you can order a plate from TPO Parts to seal the hole.
It uses the spring steel plate from the actuator to snap into place.
As for the soft rev limiter, since my RC51 will not be raced, I've perfectly ok with the 9250 soft limit.
Revving higher will gain a bit more HP, but not worth the engine reliability.
Even then, the hard limit is 10.5K, so you only gain barely a 1000 revs for your effort.

with the flapper disconnected, removing the canister and all the tubing under wouldn't cause damage or any concern for engine problems right?

As long as you've plugged any associated vacuum lines for the flapper to prevent leaks, the engine doesn't care.
The connector for the vacuum actuator is the round one at the top front of the left radiator for an SP2.
The squarish connector below it is for the left radiator fan so don't disconnect that one.
Mine was already removed and I just ordered a plate for the actuator mount hole from TPO parts to tidy it up a bit.
The whole flapper thing was to damp intake noise. I happen to like my intake noise :D

The whole flapper thing was to damp intake noise. I happen to like my intake noise :D

ME TOO, and i did remove all that stuff bty....:rolleyes:

except for the fan switch module of course

For the flapper, I used a little valve from a fish tank.:D

As for the soft rev limiter, Mike from rc51.org sent me one. Don't worry about motor issues, from what I understand, the US bikes were the only bikes with the soft rev limiter, everybody else got the regular hard rev limiter.

Directions on how to build one are on the rc51.org "free" mod page.

and then taking a vote with PC III.
then drives like the sow.:)

i too, heard the flapper removal was a must have mod for the rc. really had no idea what it entailed, just took it to my buddy's honda shop and said "do it". already running with a set of TBRs and and a pcIII. wow! i think my neighbors hate me now.

Yeah it's mostly plumbing and hardware.
Some leave the hardware in place and disconnect the solenoid and block the vacuum line. Others remove everything and plug the hole in the intake snorkel.
It was there only to damp intake noise.
It caused a big dip in power in the mid-range.

i didn't know it caused a power loss in the midrange! a noticeable loss?

When the flapper valve closes, it blocks about 65% of the intake area. If you could locate a dyno chart of a stock bike, you should be able to view this.
How much I'm not exactly sure.
And this occurs around 5000-7000 RPM, and is responsible for some fueling issues around 6800 RPM.
The Basic Racer never had this since it was for intake noise control.
This via RC51.org http://www.rc51.org/valve.htm

ah! so the dip you're talking about is BEFORE the flapper removal. i read your post wrong.

I was going to leave this alone but since it affects performance I will remove it.

Thanks,

ok now im confused so can i just remove the hose from the back side of the intake and plug it up, instead of removing everything?

ok now im confused so can i just remove the hose from the back side of the intake and plug it up, instead of removing everything?

You don't have to remove it, you can just disable it so it won't close.
Most remove the hardware to save weight and have a cleaner engine area.
If you disconnect the solenoid it will not open to allow vacuum through to actuate the flapper diaphragm.

You can see this in the diagram on the link.
http://www.rc51.org/valve.htm

I checked my bike for this and it appears it was already done. The hose was taken off, a screw put in it then with electrical tape taped backed in place basically on the flapper....if you plug the hose and it hangs loose does the old connection to the valve need to be closed?

I checked my bike for this and it appears it was already done. The hose was taken off, a screw put in it then with electrical tape taped backed in place basically on the flapper....if you plug the hose and it hangs loose does the old connection to the valve need to be closed?

If I understand you correctly...
You basically have a vacuum line from the engine to the vacuum tank via a one-way check valve to store a vacuum.
Then you have a connector to the solenoid to open and allow vacuum to actuate the diaphragm on the flapper.
If you plug the line from the engine, you no longer have any vacuum to actuate the flapper.

If I understand you correctly...
You basically have a vacuum line from the engine to the vacuum tank via a one-way check valve to store a vacuum.
Then you have a connector to the solenoid to open and allow vacuum to actuate the diaphragm on the flapper.
If you plug the line from the engine, you no longer have any vacuum to actuate the flapper.


Heres what I am talking about, the yellow circle is where the screw is inserted(behind the electrical tape, the screw head sticking out towards the flapper) the red circle is the male piece(which isn't connected, just being held by tape)I just wanted to make sure that the male piece didn't need to be sealed on the left hand side there. The hose seems to be good and plugged, but I haven't ridden enough to even tell if it wasn't.

http://i435.photobucket.com/albums/qq73/rexmitchell/photo-2.jpg

Basically he's plugged the vacuum line at the flapper actuator end instead of at the engine side. So, yes it's important to have a good seal. Otherwise you could get an engine vacuum leak when the solenoid actuates.

If you disconnect the connector at the solenoid (front of left radiator on SP2's) it won't open to allow vacuum to even reach this point.
If you want to completely remove the hardware, be sure and plug the vacuum source at the engine.

Basically he's plugged the vacuum line at the flapper actuator end instead of at the engine side. So, yes it's important to have a good seal. Otherwise you could get an engine vacuum leak when the solenoid actuates.

If you disconnect the connector at the solenoid (front of left radiator on SP2's) it won't open to allow vacuum to even reach this point.
If you want to completely remove the hardware, be sure and plug the vacuum source at the engine.

A vacuum leak from where the screw plugged the line or on the right side at the flapper valve(sorry I know Im ignorant on this). Which way is the vacuum coming from left from the hose or right from the flapper?

A vacuum leak from where the screw plugged the line or on the right side at the flapper valve(sorry I know Im ignorant on this). Which way is the vacuum coming from left from the hose or right from the flapper?

The engine's intake system is supplying the vacuum when the throttles are closed.
The vacuum line from the engine goes through a one-way check valve to a storage tank that holds the low pressure.
When the ECU trips the solenoid, the low pressure is then allowed to travel up through the hose shown in your photo to the diaphragm of the flapper actuator.
This then closes off the intake area.

If you have a leak in the vacuum line at this point, when the solenoid opens, it will be a straight shot from the engine up to this point.
The engine will be sucking air and totally screwing up it's air/fuel ratio towards the lean side.

If you disconnect the solenoid connector, the vacuum never progresses beyond that point. Then it doesn't matter what happens downstream.

The engine's intake system is supplying the vacuum when the throttles are closed.
The vacuum line from the engine goes through a one-way check valve to a storage tank that holds the low pressure.
When the ECU trips the solenoid, the low pressure is then allowed to travel up through the hose shown in your photo to the diaphragm of the flapper actuator.
This then closes off the intake area.

If you have a leak in the vacuum line at this point, when the solenoid opens, it will be a straight shot from the engine up to this point.
The engine will be sucking air and totally screwing up it's air/fuel ratio towards the lean side.

If you disconnect the solenoid connector, the vacuum never progresses beyond that point. Then it doesn't matter what happens downstream.

So as long as the screw is sealed good on the hose, I have nothing to worry about? I don't need to worry about sealing off the male connector on the flapper?

So as long as the screw is sealed good on the hose, I have nothing to worry about? I don't need to worry about sealing off the male connector on the flapper?

That's correct.

Cool, thanks for all the help man, new bike, tons of new questions....

No problem.

That electrical tape looks like a mess. Pull the hose off stick a small screw in it and push it towards the front out of the way. You wont be able to even see it barely.

That electrical tape looks like a mess. Pull the hose off stick a small screw in it and push it towards the front out of the way. You wont be able to even see it barely.

There is a screw in the hose, the PO just taped it to look like its still connected, I guess.