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AISectomy How-To!

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If you have had your ECU flashed to disable the AIS and want the system to “look” OEM or just do not want to pay for AIS reed valve block-off plates, I have a solution for you. Now bear in mind the hardest part of this procedure is removing the AIS reed valve covers, which is truly a major PITA if you do not first remove the radiator, which in itself is NOT, having done it for the valve lash check / adjust, that big a major PITA. But even if you are going to install Graves block-off plates, the OEM reed valve covers still must be removed.  It frees up access and eliminates the risk of damaging them if you also remove spark plug #2 and #3's ignition coil-over caps.
I managed with a combination of 4 ratchets, two of them are somewhat special and one is fairly hard to find anymore. One thing I can say which will make it much easier and then require needing only a standard ¼” drive ratchet if you can find one of those combination ratcheting box wrenches with ¼” at one end. An inexpensive one will do but the better ones have finer pitch ratchets, which can make their use easier in tight quarters. You’ll also then need a ¼” drive x 5 mm x ½” long hex bit and maybe another about 1-1/4” long. If you want to make it easier to reinstall the modified reed valve covers, you can replace the OEM M6 x 1.0 Socket Head Cap Screws with stainless steel M6 x 1.0 Hex Head Screws (bolts) but if you got the OEM SHCS out, reinstalling them is actually easier.
Be sure to photograph each step of this process, in particular how the reed valve come out; i.e., which way is up and forward, and also how their “flame arrestors” are positioned. I did not find in the FSM instructions on how to remove the reed valves, only reference on how to check them, though that does not mean such instructions are not in the manual (I did read I believe on the FZ-09 forum that removing the radiator was prescribed, which I thought was silly (but NOT  anymore). After their removal, I cleaned the AIS reed valves and their “flame cages” with acetone and a red Scotchbrite pad, followed my 91% isopropyl alcohol. Getting the tine screws out of them must be done carefully so as not to strip their heads, which are JIS head Philips (as indicated by the little dimple on each head). Whereas a JIS #2 Philips is not essential (a standard American Philips can be ground to almost replicate a true JIS screwdriver), an equivalent is recommended because the screws can be very tight and they each have their own captured split lock washer (I cleaned them as well and applied Red Loctite to them upon reinstallation for good measure}.
When reassembling each of the set of reed valves, apply HT RTV silicone in a fine perimeter line of the narrow mating contact surface of the reed to the reed “body”. Then, flip the reed stops 180 degrees over (invert them) from stock orientation with a dab of silicone at the contact line between the now underside of the reed stop and reed. Bear in mind that the reed and reed stops face down into the valve cover and the left reed valve is oriented opposite the right’s. Install the screws with Loctite (they also have captured split lock washers). Rather than use caps over the reed valve cover ports (nozzles) because I am reinstalling the AIS valve and hoses (my ECU may or may not have been re-flashed ) for an OEM appearance and do be double sure there’s no air movement between the air box and valve cover, I installed closed-cell polyethylene foam backer rod and the same HT silicone in the reed valve cover ports (inlet nozzles). Remove this backer rod once the silicone fully cures and prior to re-installation otherwise the backer rod will melt.
Clean the AIR depressions in the valve cover as best you can without making a mess and leaving bits of scrub pad or whatever within. Also clean the OEM reed valve cover screws of the OEM thread sealant (which can make them a bear to remove, and I do not think they need to be 20 mm long), and run them in and out of their corresponding holes a couple of times if you feel up to it to clean out the OEM thread sealant in them. Apply a bit of red Loctite to the reed valve cover screws, set in place the flame arrestors, re-install the reed valve assemblies and then their covers, apply a bit of Loctite and install and tighten the screws to spec but really only one of the 4 can be accessed and pretensioned (torqued) with a torque wrench (I have developed a TW in my right wrist over the last 45 years of wrenching).
I've done this procedure on several different bikes and not found it mentioned being done on a FZ/FJ-09 by anyone else. It has been covered I know on the Honda Superhawkforum.com, and is one part of a couple of styles of a PAIRectomy, which technically removes completely the PAIR system (AIS in Yamaha speak) and can also include installing AM block-Off Plates.
Oh, and I installed some silicone on the inlet side of the reed because even with the stop reversed the reed can still open very slightly under at least manual pressure (doubtful it would with air pressure) but I created a wedge of silicone to prevent this.
That’s it. If I had to do it over again, and this is predicated on air box is already removed mid you, I could complete the entire job in maybe 90 minutes depending how stubborn the reed valve cover screws are coming out. With this How-To and the correct tools and materials, it will take a competent mechanic maybe 150 minutes; a bit more with a couple of relaxation breaks

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Nice write up and pictures. On the FZ1 forum, several members glued a penny, with JB weld to the AIS cover to block them off. I don't see me doing this mod until I replace the spark plugs. For whatever reason, I hate removing the gas tank on my bikes.
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I was able to do it all from the front thru the radiator opening after I got it to drop far enough, i used the Graves plates and the AIS is disabled via SCU ... already had the tank off to pull ECU...
2012 wr250f - C-class 30+ age group
2015 fz-07- Hordpower Edition-80whp
2015 fj-09- Graves Exhaust w/Woolich tune by 2WDW @120whp
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Even with the ECU flash and "PAIR" off, leakage can still occur and throw off dyno runs and checking AF ratio.
As to gaining access yes you can lower the radiator and go that route but I have a radiator guard and on my bike it just seems very difficult to move the radiator once it's unbolted in any direction and after I developed my toolset it was actually relatively easy to get the socket head cap screws out though I may replace them with stainless external hex head bolts which should be even easier to access.

It is difficult to move the radiator but readily doable with care.

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There is a much more simple and easy way.
It takes marbles, ball bearings, or other suitable plug type device.
I once used a short, about one inch long, section of wood doweling.
You do the following:
It's really complicated. Seriously.
Find the hose leading to the AIS system from the air box. (It is the larger of the two breather hoses, it appears the PCV hose is smaller ID than the AIS hose.
When you remove the air box lower, you will use pliers to release the hoses from the box fittings.
Insert the proper ID sized plug. Put it in there a inch or so. If you are worried about warranty, just use a wood plug, and put a simple wood screw into it, so you can pull it back out again later if you needed too warranty the bike...
Put the hoses back on the lower air box. DO NOT PLUG THE PCV hose. Ever. You could add a cheap gauze type filter, to catch any oil vapor, it will condense on the filter, and then drip back down the hose into the valve cover, but the cover has a vapor trap built into it already, but the much cooler air box will condense the oil better, so you run less oil vapor back through your bike... Just saying...
Put it all back together. No need for JIS screw drivers, yoga moves to get at the covers and the reed valves are there doing what they do best with no air flow into the exhaust.. Absolutely nothing.
I sort of like the burble however, so putting a calculated "leak" plug into the AIS hose would be a cool mod.
Say you want some burble, but not as much as stock with the AIS working and a catless exhaust?
Put a short section of rubber hose into the AIS hose. This would remove some of the air flow, and it's super easy. You don't even need to pull the lower air box this way. :) Experiment with various sizes of scrap hose, and you can get the exact amount of burble you want.. Or just put the hose in, and stick a bolt in the end, and plug it that way. Even less work. ;) And easy to remove should you need that YES product they sold you.
Belt, suspenders and concealed carry holster. ;)
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Yes, there are much easier ways but I wanted to stop exhaust port heat transfer and gas rise down at the source, as reed valves do leak some. I considered just plugging the hose from the air box with a retractable metal rod, and I may remove the silicone plugs for stealthiness but reversing the reed valve stops and sealing the topside of the reeds IMO is the best belt and suspenders approach. The AIS is solely for emissions and does not otherwise effect the function or longevity of the engine (though it does appreciably increase engine exhaust pipe and gas temperatures which is NOT a good thing). Disabling and cutting AIS flow is also required in order to obtain accurate A/F, O2, NOX and CO readings during dyno tuning, and also eliminates the popping and afterburn effects if an AM muffler is installed (the baffling in the stock muffler masks these sounds).
In regard to other ECU changes, lowering the fan on/off temp to only 10 degrees below spec is within the tolerance that a tech would not give a second thought to being an issue.
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Has any one done any before and after measurements of A/F mixture, engine or header temps, or does the engine run noticeably better after doing this? My FJ09 runs so good after 2WDW reflash, I don't want to mess with anything. I suppose they shut off the AIS system, but I am not sure. My biggest concern is my spark plugs are really clean and look good, and I really would not want to make the A/F mixture any leaner by blocking off AIS system any further.
If red Locktite is the permanent kind, those screws will never come out again. Non-permanent lock tite is plenty good enough.
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Has any one done any before and after measurements of A/F mixture, engine or header temps, or does the engine run noticeably better after doing this? My FJ09 runs so good after 2WDW reflash, I don't want to mess with anything. I suppose they shut off the AIS system, but I am not sure. My biggest concern is my spark plugs are really clean and look good, and I really would not want to make the A/F mixture any leaner by blocking off AIS system any further. 
If red Locktite is the permanent kind, those screws will never come out again. Non-permanent lock tite is plenty good enough.
A/F measurements with the AIS operational would be meaningless. The air enters the exhaust after the combustion chamber.  It's like trying to heat the inside your car while driving with the windows down.   I've ridden some bikes (not FJ's) after a remap and the AIS was still connected.  The popping on decal was noticeable, and annoying.  I'm not familiar with 2WDW's reflashing, but their work has a good reputation.  If your bike doesn't pop on decal, I'd bet your AIS was disabled.
If your bike runs well, I'd "ride more, worry less" :D
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I'm not a tech, but this is how it works on many engines/vehicles.
AIS, or the air injection system, adds extra air to the atmosphere side of the engine exhaust, to help promote more complete burning of hydrocarbons that made it past the combustion chamber.
It also helps the catalytic converter to heat up and become more effective sooner, by adding extra oxygen to burn off fuel/hydrocarbons trapped there. They burn, and that heat makes the unit self cleaning, and more effective at converting the exhaust gas to remove oxides of nitrogen and other causes of "SMOG."
The reason you don't get the burble on the stock exhaust is not the baffles, but the CAT in the system. If you put a cat into your AM exhaust, it will also trap and heat up, and burn off the hydrocarbons too.
With no cat, raw fuel at times can pass right through the engine, out the exhaust, and as IT HITS OXYGEN AT THE EXIT OF THE MUFFLER, it lights off in popping noise and blue flames shooting out at night/day.
The fuel will not burn well in the exhaust pipes prior to that due to lack of oxygen.. Thus, AIS adds that oxygen when needed, mostly on deceleration, into the exhaust, and that helps to burn off the fuel that's NOT been burned up in the combustion chamber when the throttle was closed, but the residual fuel in the intake/engine is still pulled in, not fully burned and then passed out into the exhaust.
The reason that the "modified" fuel maps that get flashed into our ECU's shut it off is that some folks don't like the noise, and the raw fuel burning off can do damage to the muffler in extreme cases. (Lots of chemical energy in fuel. Add the oxidizer, and limit how fast the pressure can escape? And you get a bomb..)
Also the O2 sensor really only is there for closed loop operation of the engine. In closed loop, the fuel is trimmed to meet emissions requirements at the expense of power and driveability in many cases. Changing those fuel values makes the engine more responsive, but less friendly to the environment as it will put out illegal levels of NOX etc.
When you go to wide open throttle, the fuel map is determined by the program in the ECU, and the O2 sensor on this system no longer is going to trim fuel. (The system then depends on AIT, TPS, MAP and in some systems a mass air flow meter. (Not on this bike however, no MAF.) Coolant temp is also a factor. The ECU will not allow you to damage the engine until it's up to operating temps first.
The "Best" system would use a wideband O2 sensor, MAF, MAP, AIT, TPS and base fuel map that can be adapted to the changing conditions that the engine experiences. This system would be in closed loop from idle to redline, and trim fuel based on engine loading from the feedback loop constantly.
But it is more expensive, and the wideband sensors are more expensive, and can fail at a higher rate.
Anyway, nice detailed write up! :) If I ever pull my AIS, I will flip the reed valves to assure they are closed. For now I like the burble. Might experiment with some hoses to limit air flow however if I put an aftermarket exhaust on the bike.
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I forgot to mention that I have stock exhaust and no plans for any further modifications.
I thought, because I read it on the internet, decal popping was due to TOO LEAN. But according to what you are saying, too much unburned fuel would be too rich. Or maybe too lean on non-cat engines, too rich on cat engines.
Does this mean that if you want to dyno our bike with AIS, that you HAVE to block off the AIS system?
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  • 8 months later...

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