All 2st where to learn about tuning

Hi, I am about to take delivery of an '09 WR125. It will be my first two stroke motorcycle. I have read a lot about how two strokes are more sensitive to jetting and that this bike in particular can have some mid range bog. I also read that it can be adjusted out if you know what you are doing. Will my new bike come with sufficient documentation to explain how it works or should I pick up a service manual as well. I'm not shy about working on stuff when I understand how it works. Really...my other bike is a '66 Triumph Bonneville so I'm not afraid of a bit of fettling. I just want to understand how it works so I'm not just groping around, fiddling with stuff. I'm not familiar with a power valve or it's operation, though I suspect that it is pretty simple. I like being self sufficient when it comes to my bikes. Are there any good videos, websites or manuals that folks might suggest?

+1 to what Woodschick said. The service manual is a waste for anything other than specifications like torque's or gaps. There are a lot of us here that have sweated the details on making the motor on the WR 125 perform like the rest of the bike. There are several threads that show pics of the various parts on the PV linkage that you need to adjust. It is very simple once you have done it and working on the WR 125 is a pleasure. For the carburator I would go to Hall's cycles web site and download and save the parts manual for the 09 WR 125. The manual has a nice exploded view of the carb and it helps with any disassembly and re-assembly questions.

There is a lot of data from the various owners about what jetting works for where and when. I just replaced the OEM TMXX with a PWK from Motosportz and the results are really impressive. Jet it and forget it for the rest of your riding time. Definitely worth the $. The problem with the TMXX is the lack of adjustability in needles and a general finicky nature. What works today might be crap tomorrow. The low end and mid-range circuits on the PWK airstriker are far superior to the TMX and allows the carb to work well over a much larger spectrum of conditions. But your first adjustment of the TMXX is to put in the kit needle that is much smaller diameter and richer. Try the middle slot initially although I had my best results with the clip in the 4th slot down. You need to adjust your jet sizes by your conditions and altitude. Find someone in the jetting thread that approximates your area.

The second thing you need to do is adjust the PV linkage adjustment bolt all the way to the top. Some have noticed a slight loss of top end with it adjusted all the way to the top(me in my 144) but definitely adjust it at least 3/4 of the way to the top. The power valve governor does tend to dump open all at once and I found that a little less than desirable in the tight stuff. I did produce a spring kit that allows you to adjust this but I would make sure that the rest of the bike is running well before you start working with springs to fine tune. If you aren't familiar with 2 strokes and the way they run, work with it stock and get familiar before messing with the unknown.

There are a lot of things you can do to make your WR 125 better for you such as suspension work, big bore kits, definitely protection gear, etc, but with the bullet proof nature of 2 stroke Huskies you have plenty of time to explore those options. Tires: if it still has the stock Michelins on the bike rip them off at your first opportunity. I personally really like the way the Motoz Terrapactor's worked and wore on my 144 and they will work well anywhere. JMO.

Most importantly have fun and never be afraid to ask the question. No matter what it is there is one of us that has asked the same question and probably found an answer, sometimes painfully.

Congratulations and get dirty,
Walt

Ive found this carby tuning artcicle very easy to read and helpful for understanding what part of the carby affects what part of the throttle opening and
how to set your pilot jet right and main jet testing

http://justkdx.dirtrider.net/printcarbtuning.html

oops!

Thank you and apologies! I started this thread and didn't see that I had gotten these great replies!
To follow up, I went for the PWK. I have only putted around the yard with it, but it is really different at low speeds. Sounds and acts better for sure. I'm looking forward to taking if for a real ride. I haven't done anything to the power valve yet.