Originally Posted by neepuk
Who's running what jetting? Is there a common mod for the stock exhaust? I don't want to make my bike loud at all.
I have done quite a bit of research and the best I can tell is that each will need to do their own testing as different conditions will require different modifications. The consensus has been that the TW is lean from the factory. More damage is usually done lean , rather than rich. I would rather err to the rich side to sacrifice a little mileage and performance.
There are likely to be benefits in pilot screw adjustment , needle shims, drilling the air passage and re-jetting. Anything done to help them breathe will require enriching the fuel mixture.
No one seems to nail down the shims needed, but from what I see .030" to .050" may help mid-range performance. Drilling the air passage 3/32" to 7/32" offers better throttle response. Available jets #126 , #128 or #132 used to get the correct mixture for wide open throttle. Most US bikes with the late model carb got the #126 jet. CA models get the #128 and the rest of the world were equipped with #132. Once jetting is determined the pilot screw should be adjusted between 2-3 turns out for correct idle mixture.
The list of parts gathered for my 2006 model TW200:
Shims from as little as .026" to as much as .078".
Two jet sizes bigger (#128 and #132) for the US bikes with the #126 main.
3/32" drill bit
These are easy to find low dollar parts that can be purchased for under $20. Washers from the hardware store and jets from the boat shop. Easy to carry if needed. Swap if you travel from 10k feet to sea level.
What modifications did I make?
I drilled the air hole to 3/32". That was just a slight increase in size for better throttle response.
I added .046 steel washer shims under the needle for the mid range. It took two to make that thickness. The 3mm holes are slightly too large. The standard # hole sizes fit better.
Stock mine has the #126 main jet. I installed the #128. I am at 2200 ft and the air here can get pretty bad. Mile high adjusted altitude is not unusual. I have the #132 if I need to go richer.
How well does it all work?
No road test yet. It fires up good and the no load throttle seems to be better. It does not seem to stumble as bad cold as it did before.