The AIS or Air Induction System on the Yamaha V Star 650 is designed to dilute the exhaust stream with fresh air to help burn unburned or incompletely burned fuel so the bike can pass emissions tests. Many cars have similar systems to get oxygen to the catalytic converters so the breakdown can happen. As far as I know the AIS has been on these bikes from the beginning and predate the later years where catalytic converters were put in the pipes and indeed other types of motorcycles had AIS or Pulse Air systems as BMW called it back into the late 70’s.
It seems to be the first thing people do with these systems when customizing their motorcycle is ripping them off and throwing them in the trash. Some of the reasons for this are simply to clean up the looks, and get rid of excess parts that could potentially fail and introduce air leaks. More importantly for people who install aftermarket pipes removing the AIS helps stop that annoying backfiring on deceleration, however, if it was tuned properly it wouldnt do that. If it was optimally tuned for your riding conditions from the factory it also wouldn’t need it, but bikes get shipped all over the world to many climates and altitudes so they have to use general settings that will work anywhere.UPDATE: I have been reading some of the forum threads that have linked to this page and it appears to be possible to get better than stock emissions tests after the AIS is removed as long as the idle mix screws are adjusted and fine tuned. Like I said, If the bikes were better tuned it wouldnt need AIS to begin with.
There is also the theory that removing the AIS causes the bike to run cooler because it is burning extra unburnt fuel and generating more heat that it otherwise wouldn’t have. I can confirm by closely monitoring my crankcase temperature gauge that my motorcycle does seem to run about 5-7C cooler with the AIS gone, on the other hand, I also had been doing lots of carb tweaks that week and cant entirely attribute it to only the AIS.
A word of warning, if you live in one of the US states that requires emissions testing or regular inspections for motorcycles you may want to ask others in your area if you can get away with modifying motorcycles in this way before continuing. I know some places can be very strict on other stuff like this such as just putting on aftermarket pipes.
Removing the AIS to get this clean open look is fairly simple, if you are wondering where my aircleaner went I had installed the GAK kit from Ziv prior to doing this. If you’d like to try disabling the AIS to debug some other issues or you want something thats reversible look at this writeup.
Start by removing all the chrome and rubber tubes. My aircleaner was already gone but I think you may have to remove that also to get to the fittings behind it, just remove the three bolts on the cover to expose the two connecting to the brackets up top.
Then you can get remove the cover on the AIS airbox. This was fairly easy for me, I’ve heard on the earlier years they used tough lock tight on everything and you may need a small cheater pipe on your hex key for more leverage if this is the case.
Here you can see the three long bolts that secure the AIS to the engine mount that are a bitch to remove. Yamaha uses some type of gorilla strength locktight on these making them next to impossible to remove. If only they used the same stuff on say my helmet lock that fell off or the rear fender bolts that keep loosening up.
The general accepted removal technique on these guys is to take a dremmel and cut the heads off, because most of the time they just snap off anyway. Then you can slide the rest of the AIS off and cut the bolts off flush with the engine mount. A bit of black spraypaint and you cant tell they are there.
However, what I did on accident seems to have worked out rather well. I started the AIS removal after I had ridden my bike up and down the freeway a few times for an hour while monitoring my temperatures. Then I spontaneously decided to get rid of the AIS to see if that improved things. Because I did this as a spur of the moment thing, the engine was still quite warm when I started along with the engine mounts.
For me with the nice and warm engine mounts the two bolts closest to the engine were a bit difficult to get out but they came out no problem. The third one furthest away from the heat was tough. I used a regular L shaped alan wrench with 2 feet of cheater pipe on the long end to really torque it over and it still took quite a bit of force to get the bitch to turn. Slowly but surely an 1/8th of a turn at a time I got it out of there. You can see I had to remove the floorboard to get better access to some of the bolts.
Next the AIS elbows. Heres a good example of what NOT to do! I thought I’d just use the pointy end of my old spud wrench to twist the front one back and forth while putting pressure on it from underneath with a crowbar against the engine and just work it out. Nope, that does not work at all! Two hours later after much swearing, tool throwing and sweaty and completely worn out from the awkward position I had to take a break and call Patrick to find out the front elbow removal trick.
Heres the correct way! Use a long screwdriver or crowbar between the down tube and the front jug from the SIDE. Put it up under the elbow and just hammer on the end of it and sure enough the front elbow came out in 5 or 6 blows. Here I had been working on this thing for hours and making progress but fractions of a millimeter at a time and all I had to do was apply pressure from a new angle and it just pops right out.
For the rear jug you need a slide hammer, trust me on this. Theres no room to lever it out and no room to twist it out, the only way is to pull it out.
I’d been to every tool store in the land and everyone looked at me like I was from Mars when I asked the clerks if they had a slide hammer. The guy at Ace Hardware said he’d been working in “tha tool b’ness” for 60 years and never heard of one. When I described it and how it worked “hey, now thats a great idea, someone should make a tool like that, I bet you’d make some money.” Uh yeah. The other stores were even less helpful, Home Depot, Lowes, Pep Boys, Autozone, Sears website said they had some but not in person, nothing!
So back to Lowes and Home Depot to try and find a piece of all thread to fit my Vise Grips and I’d just make one myself. Neither place has all thread in the right size! However, this time the clerk asked me what I was trying to do. “Oh like a dent puller, I’m not supposed to tell you this, but you know you can rent those at Checker.” SWEET!
The rental ended up costing me $40 up front and the tool was mine for 48 hours. When I returned it, they refunded me the full ammount so it was basically free. The clerk said if I didnt return it in time then I just get to keep it, and it was actually a few bucks cheaper than buying the same thing (which was out of stock). I’m not exactly sure how they make any money with that business model.
Checker Autoparts did have the slide hammer to rent, but they didnt have the adapter for it. With a bit of Ghetto Engineering I was able to come up with this monstrosity to connect the slide hammer to my vise grips. Did you know that most places only carry a limited selection of metal pipe fittings now days, everything is PVC.
Slide hammer into 3/8 by 3/4 bushing into 3/4 – 1″ bushing into 1″ union to 1″ – 1/2 bushing which fits over the knurled knob on the end of the adjuster part, Simple.
Just 3 whacks with this and the rear elbow came right out. Remember to remove the side cover before you try this. Assuming you had all the tools ahead of time and the knowledge of the proper way to get these out learning from my mistakes you could get both elbows out in under 5 minutes, not half a day like it took me.
Here are the components for the Night Sky Customs No Chirp AIS Removal system. It consists of these polished aluminum and very nicely machined bits. I’m very impressed with the quality of their workmanship. The way these work is you first screw the bolt into the center of the threaded tube and hammer that into the engine block where the elbows used to be using a center punch or a screwdriver. Then you take the bolt out and do the next one and tighten the polished caps down on top of that.
The theory is that leaving a tube in there and capping it off will keep the internal operation of the engine the same and not introduce a squeal or chirping noise that plugging the hole with something solid could do.
Piece of cake to install these things. The installation bolt fits a bit loosely and I thought that might mangle the aluminum threads and make it a bit difficult to unscrew after hammering on it but I was able to unscrew it with my fingers after it was in there solidly.
The polished caps also end up hitting the engine case before snugging down on the threads so I was a bit worried of them getting loose and falling out or getting an air leak. I coated the threads thoroughly with red locktight and tightened them down as tight as I could with a penny and some vise grips. 6,000 miles later they havent budged and no air leaks.
There are also several alternative methods for sealing the AIS ports that many have used successfully. If pulling the elbows out seems a bit scary for you, you could just leave the elbows on there and seal them with a compression nut like whats used in copper pluming fixtures.
You can also just seal the elbows with a bolt with lots of high temp RTV gooped on it, just dont start the engine for 24 hours and allow the stuff to fully cure if trying this way or you’ll blow out the bolts and have to start over.
If you like the cleaner look of having the elbows out and are too cheap to spring for the Night Sky Plugs you can also seal them with a 45 cal ACP shell. According to Patrick its a perfect fit. Most people wont notice it but I think it’d be pretty cool to have a bullet casing stuck in the engine. You should be able to go to any gun range and get a pair of empty casings for free if you dont have a pile of your own in your back yard.
Theres also the solid plugs that you can use sold on eBay, but like was mentioned earlier I dont think these are a good idea and its not as easily reversible. If for some reason you change your mind it requires drilling the solid plugs without going too deep and getting shavings down in the engine and threading in something to pull them out. For that reason alone I would avoid the solid plugs. All the previous mentioned methods retain that hollow air space the way the engine was designed.
Next all you have to do is make sure the carb sync ports on the intake manifolds are capped off with the included cap from the Night Sky kit and the existing stock one on the other side and you’re done! Or you could do what I did and just keep the first section of rubber tubing attached and thread a bolt up in the end. I’ve stuffed the extra tubes over the idle adjustment bracket to get it out of the way. With the tubes on there it makes it much more convenient to sync the carbs. All I have to do is attach the sync tool to the end of the lines, no more trying to attach tubes between the cylinders of a hot engine and burning my hands.
This turned out to be a fairly simple procedure, after I figured out the correct way to remove the elbows, and was not near as scary as I made it out to be in my head. Anyone can do this fairly simply with the install of their after market pipes.
UPDATE: With the Nightsky plugs next to impossible to find now the best way to seal these ports is either the .45 ACP shells or leaving the elbows in and using RTV with a bolt.
Using a SPENT .45 ACP shell tap it into the AIS port hole, others who have done this tell me it is a perfect fit and no epoxy or sealer is needed. Here are some pictures that have been sent to me showing how it looks when done: