Jetting

Now that the carbs are nice and clean outside, it's safe to open them up and expose the inner workings. It was at this point that I began to realize one of the benefits of single life (there are so few). I was able to bring my set of carbs into my living room so I could do the rest of the work while sitting in front of the TV watching the football games with absolutely no guilt. Pages 5-2 through 5-9 of the manual deal with major overhaul and testing of the carburetors. The drawings are useful for identification purposes, but no further disassembly is required beyond removing the float bowls and the diaphragm top covers. The manual also fails to explain how the Dolphins could have been so completely humiliated by the Jags. ... oh never mind, time to start another load of laundry and begin the rejetting process.

Carb Guts

Before doing anything else, it is important to get all the dirty work done. The drilling out of the pilot screw plugs will create some small metal filings, so lets do that before opening the carbs to possible contamination. Turning the carbs upside down, locate the small plugged holes which need to be drilled out to expose the adjuster screws. The picture included in the Cobra kit is slightly inaccurate and the manual gives no clues here. Notice the pictures of the location of the drilled out holes in my carburetors for identification. Using the 5/32 drill provided with the kit, drill out the center of the small plug. A variable speed drill is best because you must pull back or stop immediately as the drill breaks through. The instructions recommend the use of the sheet metal screw provided to remove the rest of the plug. Good luck! After a frustrating attempt at this method, I decided to try a slightly larger drill bit, probably 3/16. This enlarged the hole enough that the rest of the plug just came out easily. It is very important not to let the drill break through because it could contact the screw and possibly tighten it to the extent that it could cause some damage. Now blow away or rinse off any metal filings before proceeding.

Cobra Jet Kit - DynoJet

Cobra™ Jet Kit

The Cobra jet kit comes with all the necessary bits and pieces for setting up our bike for two different configurations. One set of jets (Dynojet #104 and #106), is for use with slip on mufflers with baffles, and one set of jets (Dynojet #110 and 112). for use without baffles. No jets are supplied for use with after market filters, so we will need to figure that out through trial and error. Replacement main jets can be purchased for about $3.00 apiece, so I purchased a selection of sizes. I chose to start out by trying a #130 for the rear and a #132.5 for the front carb. When ordering these jets, it is important to specify that they are the small slotted type, not the small hex or the large slotted type.

Turn the carburetors upside down to remove the float bowls. The four screws that attach the bowls are going to be difficult to remove for the first time without stripping the Phillips heads. It is a good idea to grip the head with a small vice grip type pliers to loosen them first. Then remove them the rest of the way with a Philips screwdriver. hold the hex shaped needle jet with an 8mm box wrench and remove the small main jet and replace with the new jet. Do the same to each carb, being careful that the correct jet is in the correct carb. For reference, right hand carburetor is for the front (#2) cylinder, which gets the larger sized jet. The pilot jet and starter jet are indicated in the above picture for reference. They are not being replaced. Making sure the o-ring gasket is still in place, replace the float bowls. It is not necessary to emulate King Kong when tightening the machine screws. A little more than snug is plenty. Be careful not to strip the heads.

Turn the pilot screws in until they are lightly seated, and back them out 3 turns each. This will be close enough to get the bike started. The fine tuning will be done later when everything is running and when we synch the carbs.

Setting the Jet Needles

Turn the carburetors back upright on the bench and remove the black plastic diaphragm cover from the top of one carb. Do one at a time so as not to mix up any parts. Remove the rubber diaphragm from the carburetor body and look inside the recess on top of the diaphragm/ throttle slide. Notice the small gray plastic tab that is inside this recess. Using a small needle nose pliers, reach inside and gently pull this tab out with a slight twisting motion. the only thing holding it in is a small o-ring inside, it is just a snap in deal. It should pull straight out fairly easily.

More Carb Guts

Pay careful attention to the arrangement and sequence of the small parts that make up this needle assembly. They need to go back together the same way.

The Dynojet instructions call for the clip to be in slot 3. Since we are replacing the airbox, we will use slot 4 as a starting point. Half settings can be attained placing one of the small shims provided under the clip. One final point about the needle setting. When the needle assembly is placed back together, the top of the needle will be inside recess in the small plastic holder. There should be some up and down play of the needle against the small spring when everything is put back together. This all works out fine in slot 3 or higher, but when the clip is lowered (needle raised) to slot 4 or 5, there isn't enough room. The needle has to be modified slightly by filing or grinding some of the top to allow some free play. Check the notes in the illustration.

Slide the needle assembly back in to place with the parts in the order illustrated. Using the small needle nosed pliers, push the small plastic holder back into its seat until the o-ring holds everything in place. Check the needle for a small amount of up and down play against the spring inside the throttle slide. Slide the slide throttle/ diaphragm back into place in the carburetor body making sure the needle is located in the needle jet and that the diaphragm is located correctly in the groove at the top of the carburetor. Make sure everything moves freely and replace the large return spring and the carburetor top with the four screws. Repeat all the procedures for the other carb.

The carburetors ore now rejetted and set to be returned to to the bike. Any further changes to the jets and needle clips (and there should be a few more tries before this experiment is done) will be done with the carburetors on the bike. The only reason I chose to remove the carbs was to facilitate the drilling out of the pilot screw plugs, and to be better able to see the whole picture. All that is left for this phase of the operation is to re-install the carbs and finish solving the problem of how to fit the K&N air filters to the carburetors.

Meet JAK - Jumbo Air Kit

As if being played out in a sequel to a Japanese horror flick, BAK was born and implanted into the bodies of various Yamaha motorcycles to go forth and terrorize the streets of civilized society, until it reached the land of Oz where it met up with Mark Jelic who fathered a new creature named GAK. Well here we are, released just in time for the holiday season and coming soon to a theater near you. (sound of a gong in the background) It's JAK son of GAK, not recommended for younger theater audiences.

The whole topless idea had to be scrapped for the sake of public decency (it would have earned an R rating). Since the TAK was too big to fit under the tank without major alterations, and since the filters chosen were the largest size available for a 2 1/8 inch carburetor flange, the logical name for the son of GAK is ... JAK - Jumbo Air Kit. And so it was and so it shall be. God help the world when this beast is fully grown and unleashed upon the poor unsuspecting public. Harley riders will run for cover as the trembling earth announces the arrival of the latest V-Star 1100 to the neighborhood.

That's it for now. I'm going to return to the garage and reassemble all the goodies to working order. By next month, I will have everything running, the settings dialed in and dyno results and printouts to be shared with everyone. I just need the weather to get back up into the survivable range and ride this beast to New England Performance in Hempstead, NH for dyno testing. I still have a bit of riding and tweaking to do before then.

Next month, we will be getting into detail about valve adjustment, carburetor synchronization, and the final adjustments to the needle jet settings and main jet sizes for the final configuration.

Parts is Parts

2	K&N Filters		Dennis Kirk part# 30-1570	$30.99 each
1	Cobra Jet Kit - Stage 1		Dennis Kirk part# ???	$75.99 each
2	Mikuni Main Jets	Sizes to be determined		$3.00 each
2	Tee Connector	1/2" Barbed
1	2" ID Muffler Connector	(2 1/8 OD)
1	2 1/2" ID Muffler Connector	(2 5/8 OD)
1	1 1/2" Fernco coupling
1	1 ft length of 1/2" hose