Carb rejet/mod

[Dave63]

I recently replaced the stock a/f mixture screw with an EZ-turn screw, and after a summer of being caught in the rain, it seized in the threaded bore. Knowing that without a spare carb sitting on the workbench, trying to remove the soft, brass EZ-turn screw would result in it breaking, ruining the carb all together. I scored a new carb, (Thanks Dean-O) and this whole gig is to show me swapping over my “custom” parts, and so others can see the locations of pilot jets, main jets and diaphragm/jet needles.




First you need to remove the carb. Remove the air cleaner, and backing plate. The backing plate on the Evo is basically the mount that stabilizes the front of the carb. Unhook the fuel line and both throttle cables. Although not necessary, I mark one of the cables to make sure I don’t get them mixed up. It’s hard to mix them up, just due to their length difference, but anything’s possible. To loosen the throttle cables, just uncover and unadjust the cable adjusters near the throttle, under the little, black rubber boots. Shorten the adjuster, putting slack in the cables.


You’ll also need to unhook the VOES vacuum line and the float bowel overflow line. Just let them hang.
On the left side, (shift lever side) you need to unhook your choke cable. It’s a 5/8” nut on the back of the mounting bracket/motor mount. It’s easier to unhook the choke there, then off the carb, IMHO. Once your cables, fuel line and cables are disconnected, the carb pulls out of a rubber grommet/seal that’s in the end of the intake.
Once off, I drain mine by removing the bowel over a container. With the carb upside down, and the bowel off, you’ll see the float, and two ports for jets. The larger port (top) is for the main jet, and the smaller one (at about 9 oclock) is for the pilot jet.



This carb is stock. It’s so virgin, the a/f mixture screw was still capped. Too boot, the factory a/f setting on the screw was barely 1/8th of a turn out. Yep…..from the factory.

Stock jetting for this was 170 main and a 42 pilot. I have V&H straight-shots and an A/N air filter. I run a 180 main and a 45 pilot. The jets a re brass and soft, so no need to tighten them like a lug nut on a dump truck. You'll not how long the main jet "looks" in this pic, because it's still attached to the emulsion tube. Separate them to replace the jet.




Take care not to hit or press on the float, as you’ll have to reset the float level again, and that’s another story for another day. Not difficult, just another few steps. Put your float bowel back on, before taking anything else apart. Sometimes it helps to have a small selection of jets, to be able to change them at will, for best running results. Numerous jets come with a Dynojet kit. Others can be bought at your dealer for a few bucks.

[Dave63]

Next….lets remove the diaphragm cover and all the stuff in there. Once apart, lay it out. You have a diaphragm w/slide, a jet needle, a plastic spring perch and a spring.

If you’re using a Dynajet type jet needle, it has an adjustable setting. Mine’s set on the 4th ring/slot from the top. You can also use a jet needle from a 1988 XL/Sporty carb, (slightly shorter and a rounded tip) part # 27094-88. Some guys use the stock needle, and shim it up a little with 1-3 small #4 washer (0.05” thick) UNDER the needle, to allow for a richer setting/adjustment.
The Dynajet diaphragm spring is lighter, allowing for quicker slide movement and throttle response. My slide air bleed hole is also enlarged, which is simply as easy as drilling it from stock to 1/8” diameter. This allows for more vacuum/aire transfer, assisting in better throttle response. The airbleed hole is the hole in the slide that is NOT in the center. It's off center, as the needle travels down the center hole.

Next, I needed to remove the stock a/f needle and replace it with my EZ-turn screw. Adding a little antiseize to the threads will hopefully stop the sticking issue I had.
Here’s the location of the capped off needle.

Drill a 5/64”-1/16” hole in the center of this aluminum plug. Afterwards, insert a small sheet metal screw. Get it in there nice and tight. I used needle nosed pliers to pry the cap out, using the bottom of the carb bowel as the prying spot. It didn’t take much, but the screw has to be in there good, it it’ll just pull out.

[Dave63]

After the cap is out, you can adjust it as needed. Usually, 2-2.5 turns out from full IN is a good starting place. Here’s the example of the EZ-turn needle, vs the stock one.
[IMG]http://img.photobucket.com/albums/v364/lucygoose1999/IMG_23
74.jpg[/IMG]
Once together, place back on bike, reattach everything and start the bike. Don't forget to readjust your throttle cables, for pull and return. I also like to use a little silicone grease, (sparingly) on the carb grommet, where the carb slides back into the intake. The silicone helps lube the carb as it slides in, and prevents it from sticking to the carb later. Silicone is also good for rubber.

It has to be warm to set you’re a/f mixture and idle, and that usually takes about a 2-3 mile ride or so. If you’re modding the carb, you’re a/f adjustment of 2-2.5 turns and your previously set idle adjustments are enough to get you down the road, but once warm, tweak it a bit more for best results. Hope this helps some of you guys out.

[Dave63]

Polished Venturi and Slide...

Before:



After:

[Kainam]

Nice work!