Modern Vespa

Hi all,

I did a search but didn't find this. I got the tool to adjust my a/f mixture on my GT200 (Keihin CV carb) but can't find the damn screw. I know where the idle adjustment screw is (right on top, heh) but where's the mix screw? Maybe someone has or can point me to a pic?

I checked the workshop manual but didn't see it.

Thanks!

ian

It's on the left side, at the front and near the bottom. Very difficult to engage a screwdriver because you can't see the head. Try sticking a mirror down there.

You will need a small screwdriver, about 2" long.

Mike

isnt there an actual tool you need?with a 'D' shaped head?

EPA doesn't want us adjusting our shit, so we get the "tamper-resistant" hardware. The rest of the world just has a regular screw.

Here you go. View from the left side of the scoot. I've been getting all too familiar with the carb lately.

JimBo's photo shows it. I know on a 2006 GT200 you need a "D" shaped tool to adjust it. I'm not sure, but I think on the earlier GT200 it doesn't require the "D" tool and can be done with a screwdriver (maybe someone with an earlier GT200 can verify this). Incidently, you can easily make a "D" tool by going to a hobby store and buying a piece of metal tubing of the appropriate size and then flattening one side with a squeeze with a small pair of needle nose pliers. The size I used was 7/32 X 0.014 (5.56mm X 0.355mm) in aluminum. I also made one out of brass and it seemed a little more solid to use but both worked great. Or you can do it right and order the real tool on line. I know Scooterwest has two to choose from. I hope this is helpful.

Come to a Quitters meeting and I'll buy you a beer. This is perfect!

I've done this adjustment several times to find the "sweet spot" in the mixture to balance power, fuel economy and keeping the ignition cool - too lean (more air) makes ignition hotter and can gack up some less tolerant carbed machines. The key to the adjustment is moderation - 1/8 to 1/4 of a turn in or out at a time was where I stayed. Info on this board says most GTs come more or less 2 turns out from full seat from the factory. For mine, I turned the screw all the way in - being gentle as not to damage the needle or needle seat inside the carb - then went out a full two turns. I bought the D tool from ScooterWest (works for my GT and my wife's LX) and marked it with a Sharpie to help keep track of the number of turns. It took me about a week of adjusting both mixture and the idle speed, riding, adjusting and more riding - on streets and freeways. My perfect setting is pretty close to 1 5/8 turns out from fully seated It's leaner than stock, but perfect for my setup and riding style. My fuel economy rose phenomenally (on the order of 30%), and my PM pipe pops and backfires a lot less. I also enjoyed the process, as it made me pay closer attention to the "feeling" of the bike and it's running condition and it was very satisfying to get it "just so." Enjoy!