Thread: DR350 Thread
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Old 01-06-2013, 10:33 AM   #14105
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Joined: Feb 2006
Oddometer: 2,853
Originally Posted by visovm View Post
With regards to the "pilot screw" I will call it that from now on since that is what its called in the service manual.
That's a safe bet.
The consensus seems to be to start with 2-turns out and than adjust from there once the bike is warmed up.
Procedure for adjusting the idle mixture:

Warm the engine up. Set the CO to between 3 and 5%. Check and or reset the idle speed. Recheck the CO%. If you do not have access to a gas analyzer, lower the idle speed a little bit (this increases the sensitivity, so you can more easily notice the effects of your adjustment). Adjust the fuel screw in until you notice it is running worse, then adjust out to the point where the idle is the strongest, and then no more than 1/8-1/4 turn further. Adjust the idle speed back to normal.
If you look back at my previous pictures you can see that the slide is already drilled with one hole on either side of the needle. I believe this is how the carb came stock, but for reference the top of the slide looks like this:

Two holes are stock, but you can check to see if they have been enlarged by having a look down inside the bores. The walls should be smooth (as molded), with no drill marks.
As far as I can tell it does not look like the needle was ever shimmed with washers and the spring does not appear to be trimmed. Judging from the responses I should leave it this way.
I would not clip the spring or shim the needle, but I might install an adjustable needle with a suitable profile. Aluminum would be preferred as a material, as stainless steel and titanium can accelerate emulsion tube wear. Machining extra clip grooves into the existing needle would probably work well.
Likewise, the best way to improve performance and throttle response would be to get a jet kit or spring for the TM33 carb, instead of fiddling with shims, and trimming of the spring.
The Factory Pro jet kit is likely to contain a needle with a suitable profile, but it is made of titanium. The DynoJet kit is not as likely to contain a needle with a suitable profile, and I'm not sure if it's stainless or aluminum.


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