TTR 125 Problems

Lol, at this point this TTR may be buried with me. Feel like I'm pretty damn close to cracking this code.............bike kept dying with any gas, and went and took a look and the guy I bought this second carb from had shimmed the needle (btw, I now know what those words mean) to run leaner. Moved that shim to other side and it's much improved, but will throw a second shim in there and see what that does. Also have a 20 pilot on the way (17.5 in there now), and am going to put a 110 or larger main in.

There's a noticeable sound from the valves clickity clackiting now (they were wayyy tight and I adjusted), but doing some research and it seems like it's fairly common that they go from too tight to being audible (and have watched some videos of guys with legit valve issues, and this bike sounds nothing like them). Once I (hopefully) get the stumbling figured out, I'm going to uncork this thing and rip out the shitty airbox and spark arrestor and try to open it up a bit.

You can see in this video that if I'm real deliberate on the throttle it gets to WFO okay, but if it's sudden it'll just bog/cutout. It's 100% better than it was before I re-shimmed it (where it would die no matter how smoothly I applied throttle), but methinks it needs another shim (or two).

FWIW, I feel pretty comfortable with carburetors at this point *shrug*

Bike starts first kick every time (without using the choke), idles great, so it's just getting the jetting/needle right and it should run like a top.

https://www.youtube.com/shorts/TCM6ogHg7L4

 

If it idles great, why are you changing the pilot jet?

 

I think the pilot controls up to 1/4 throttle, which is where it’s running lean when I crack the throttle aggressively.

 

It’s cool how you have jumped in and are learning about carbs.

I don’t know your carb or bike, but the carbs I have always worked on, the needle drops down into the slide. When you shim the needle it actually lifts it up so it doesn’t extend into the main jet as much. Therefore, when you shim the needle, it raises the needle higher, like you are already twisting the throttle, and makes it richer, not leaner.

 

Does this carb have an accelerator pump?

 

Yeah, sorry that wasn't super clear - the TTR (depending on year) only has a fixed position on the needle, so to raise or lower it needs shims. The previous owner had shimmed it down, making it run leaner........once I flipped that (and raised the needle up), the throttle response was much improved.

It doesn't. Got my 20 pilot delivered last night so might try to futz with it today and get it totally done (also installing a new petcock and some other odds and ends), but I'm been googling "how to know when you hit your thumb so hard with a hammer it broke" this morning so I've only got nine functioning fingers.

 

Installed the 20 pilot and also installed a 115 main.

I think I'm declaring this war over and yours truly the winner. Now just need to install the new petcock I've got and the 90* inline fuel filters and put the plastics back on and she's ready to rip. Still debating over fully uncorking by modding the airbox and silencer for more airflow. Prolly will, but would love to keep it stock for stock 100 endurance racing.........but would also like moar powah.

 

IF you uncork it you will need to rejet. Remembre if you let it breath better it is going to need more fuel or you are back where you started with e to lean to run conditon.

 

Yup, I'm with you - that was one of the reasons why even though it idled "fine", I put a 20 in. The 115 main seems to be overkill for the stock airbox setup, so am uncorking (took out the snorkle, but haven't cut an additional hole in the airbox yet) and will turn in the air screw to the factory setting of 1.5 (was at 3, then turned to 2 when I installed the 20).

Without taking out the snorkle, the bike was stumbling at WOT because of how rich it was running with the 115. Will report back.