I have  Raask exhaust and a K&N slab filter. I have 55 pilot and 150 main jets installed with a 3/4 white spacer mod. I have a Dial-a-Jet installed. The mixture screw is 2 3/4 turns out. I drive around at roughly 1000' altitude. The plug looks good.
The specific problem I am having is the idle drops down too low, sometimes to the point of stalling, when I let off the throttle quickly from about 2000- 2500 rpm or higher. I have replaced the spring and the diaphragm in the TEV, and cleaned the carb thoroughly twice.
This problem disappears when running with the choke out one notch- in fact the bike runs much smoother that way, except that it is too rich.
Would going up to a 57.5 pilot be the solution? I ask because I have never heard of anyone running a pilot that large.

I remember when mine ran smoother w/ 1 notch choke. But it did that from day one.
But how do you figure it runs much smoother when choked, but yet runs too rich ? That just doesn't add up.

Normally if its running lean (1 notch choke) in the low to midrange, the white spacer mod fixes it. But you already did that, so you have to suspect there is another issue. Seems this all started when you modded the carb to get rid of backfire. This is one reason why I warn against it.
I have read of a lot more carb problems after modding, than before.

For several years Ive had to use choke to start & idle, even on 80* days,,

Now, Ive cleaned the carb & got the slide in Clean & Dry. It runs better than ever,, If the pilot doesnt smooth things out for ya, give pulling the slide & cleaning inside the cab & outside the slide,. I dont think I got it right the first time,,

Where to get it?

I have had the carb completely apart, and cleaned it twice- all the passages, jets etc etc. with wires and carb cleaner and compressed air. It is clean.

Routy wrote on 06/22/12 at 08:12:20:

It runs rich because I don't tune the idle screw with the choke out. I probably could try that, but what good would it do?
And I replaced the spring and diaphragm in the TEV with new parts. (that little diaphragm cost $70! )

arteacher wrote on 06/22/12 at 07:44:08:


K&N filter and a Raask and you only did a 3/4 white spacer mod ?
The K&N and Raask moves more air for you so you need more fuel to mix with it.  The Dial-a-jet picks up in the mid range but you could still have a lean spot in the 1/4-1/2 range.  I would go to at least 1/2 white spacer, if not a bit more to richen the low-mid range crossover.  If you have a good distinct setting on your pilot jet then you could possible to to a #57.5 to try.
I have a stock S40 with a small cone filter and an Emgo reverse cone muffler from RYCA.  I am currently running a #52.5 pilot with the screw at 2 3/4 turns out and a #52.5 main jet.  It runs smooth and strong and have twice hit 105mph indicated on the speedo  on a flat freeway run.
The Emgo is as flow through as a muffler gets, at least as much as a Raask.  I've not tried a #55 pilot or #155 main jet yet but will this weekend and see what if any difference that makes.

Report back: The idle dropping problem is no better. However, the bike runs a lot smoother, acceleration is stronger and more even, and it hardly ever pops between shifts, and didn't backfire at all. The idle seems more even as well.
BTW, I installed an oil temp gauge and the oil temp was 248 deg after a 45 min ride in city and country. Is that about where it should be with the ambient temp at 86?