There has been a lot of discussion in the ISRA forum, about popping on deceleration. The consensus of opinion seems to be that the problem is most often the by-product of the Air Induction System (AIS) included with the V-Stars in its stock form. The AIS burns the unburnt exhaust system gases by way of injecting fresh air at the exhaust port. According to the Yamaha service manual, this is done in order to reduce the output of the hydrocarbons released into the atmosphere.

Right-hand view with airbox removed

Several ISRA members have come up with innovative ways to remove the AIS or to disable it in order to eliminate the popping. Some owners have completely removed the AIS canister from the front lower-left corner of the frame with all of the tubing that surrounds each of the cylinders. They then plugged the spigots at the cylinders. This plugging has been accomplished in a number of different ways, such as inserting concrete anchors or capping the spigots with vacuum plugs. There has also been some concern about the repercussions of completely removing the AIS in the event that one's bike must be subjected to emissions testing in order for it to be licensed. For that reason, an alternative could simply be to disable the AIS but leave all of its core components in place.

Left-hand view, unmodified

Because of all the attention given to this topic, I found myself thinking about it more and more often. One afternoon while standing in my garage, looking at the bike (it's hard not to spend a lot of time doing that when not riding), it finally occurred to me, all that one needed to do was simply block the rubber portion of the AIS tubing. This would be a pretty simple job since I had removed the air filter and its cover during my BAK (Big Air Kit) installation last summer.

If the air filter case assembly is still on the motorcycle, disassemble it by removing the three allen head screws that hold the assembly to the brackets on the bike. Then, disconnect the air-duct at the top of the assembly. Once that's out of the way, begin disabling the AIS by sliding the hose clamp from the rear cylinder rubber hose down onto the metal tubing. By applying an appropriate amount of wiggle, the rubber can easily be freed from the metal tube.

AIS disconnected from rear cylinder

I spent a fair amount of time experimenting with different items for use as plugs. I test-fitted a number of different items and, for various reasons, was dissatisfied with them all. First, I tried a wooden dowel. It probably would have worked okay, but I didn't have one in the appropriate size and wanted to be sure I didn't use anything flammable in this area. I tried cutting the head off a bolt but decided that was too difficult. Finally, I stumbled across a possible solution, I test fit a lead bullet. Fit pretty well, the tapered head made it easy to insert. It was close to being a good solution since the fit was right, but it was heavy and lead is a poison. I was also not sure I would be able to easily insert the bullet far enough into the rubber hose to allow reattaching it to the metal tubing. Then, with a burst of inspiration, I decided to try the other end, the shell! I thought that the copper jacket would work well since it was light in weight and the hollow interior would allow a screwdriver to be inserted to push it far enough into the rubber tubing.

Get's 'em every time!

The next part of the modification requires several tools that may or may not be part of the average motorcyclist's toolbox. The end-product should be a .45 ACP brass case with a spent primer. But we'll go through this step-by-step, since using a live primer could prove disastrous! There are, of course several appropriate choices in tools used to make an inert primer. A Colt Government model, such as the Combat Elite shown here, is always appropriate, but of course anything that will fire a .45 ACP will work. The nail in this case, would need to be an unfired .45 ACP cartridge. Load a magazine and fire a round. That's all there is to it. Now go find that spent shell that ejected somewhere on the ground.

Un-fired cartrige

Since this a description of a motorcycle modification and not a shooting lesson, suffice it to say that all appropriate safety measures should be observed to ensure that the cartridge is fired in a proper manner. It is firing the cartridge that results in a spent primer. The reason to use a shell with a spent primer is that the primer fills the hole at the bottom of the shell and provides a surface against which to seat the shell in the rubber tube. It also ensures that less high-temperature RTV is needed to seal the shell in the rubber tube.

Empty shell casing

Back to the motorcycle. Apply high-temperature RTV to the bottom of the shell and around the ridge just above it. Insert the shell into the rubber tube with the hollow center facing out. Using a screwdriver, or similar tool, push the shell approximately an inch into the rubber hose. Make sure that the shell is positioned such that there is sufficient room to reattach the rubber hose to the metal tube without introducing any kinks in the rubber hose. Reassemble the rubber tube onto the metal tube and reattach the hose clamp.

AIS hose with shell inserted

Okay, the rear cylinder is done. All that's left is, "lather, rinse, repeat" for the front cylinder. Let the RTV set up for about 24 hours before you fire up the engine. Let's go for a test ride. Make sure the bike is good and warm, then go find a nice long downhill grade. Close the throttle entirely and let the bike run down the hill. Is the popping gone? Yes? Great! Now, for the acid test. Crack the throttle open just a little, but not enough to provide any acceleration. Is the popping still gone? If the answer is yes, proceed to the third step in the test, which is roll-on and go find some curves. And don't forget to grin from ear-to-ear when you tell your friends that you solved an annoying motorcycle problem with help of a simple, every-day, handgun. <g>