Yup. I recently went from the stock 145 main to the 150, up on the pilot and 3 washers in place of the spacer with a Dyna muffler. Purrrrrs like a tiger.

In the carburetor is a throttle slide. It is a large black plunger. Mounted to the slide is a "needle" which is actually a slightly tapered rod. The slide controls the amount of air entering the engine. The needle inserts into a "jet" which is actually a brass plug with a hole in the middle. The needle moves with the slide, and controls the amount of fuel passing through the jet. The fuel passes through the space between the needle and the hole in the jet. The "white spacer" is a white plastic washer, which positions the needle against a spring in the slide. Removing or thinning the spacer allows the needle to rise slightly in the slide, allowing slightly more fuel into the mixture, richening the mix in the midrange where the needle controls it. At wide open throttle the needle is pretty much all the way out of the jet, so the jet size controls fuel mixture.

@Charon, that's was exact what I was looking for! Thanks a heap. I'm definitely sure that the next person who searches White Spacer Mod will see this! But I didn't look in the Tech section. I'll do that next time.

@Routy, I must admit that I am not very handy at mechanics. Is this mod something you recommend me trying to do? Can I really mess something up? It's definitely not worth taking to a mechanic for sure tho, huh?

Strictly speaking, neither you nor your motorcycle dealer can do the mod. Doing it is a violation of Federal laws against increasing engine emissions. Nor can you do any other modification to the intake or exhaust system which will increase emissions, including noise emissions. As a practical matter, you will probably get away with it because there is almost no enforcement at the individual level. You have been warned.

dhtran wrote on 09/20/09 at 14:55:53:


While simple in principal, the tool techniques might prove challenging.  Depending on the condition of the things.  And some problem solving might be required.  

Ideally, it shouldn't be hard.  But if the machine screws holding the top of the carb are difficult to remove, then you'll probably have to remove the carb from the bike, which is a bit interesting.  Then be faced with the challenge of stuck screws.  Getting the needle out is no trouble, getting it back in might be less easy.  

We used to do this type of thing all the time for cars and faced similar troubles.  I don't know that motorcycle shops do it.  One would think so, given how lean many bikes run.

" except it gets a little challenging in a couple spots, like getting those 2 little screws threaded back where they belong. "
Here is a trick you might try. If you  don't have a magnetic screw driver to told the screw heads in place simply stick a small magnet to the shank of your screw driver. The tip will hold a magnetic charge until you pull the magnet off.

And make sure you get that little round plate right side up so that the slots line up correctly w/ the 2 holes.

And getting the outer edge of the rubber diaphram to stay in the groove till the cover is put on, was a little challenging also. I used some heavy sticky grease there too.