So I've had my TC250 dialed in for some time but all of the sudden, it started running like crap. There is no reason I can think of for the bike to start running poorly. It has a mid throttle sputter and inconsistent bog that gets worse after a few laps at the MX track. The first lap is fine then it starts to sputter and gets worse after a few laps. I tried changing a bunch of jets and nothing helped. Plug looks good and valves are in spec. Current jetting is JD red needle in clip #4, 180 main, 42 pilot, fule screw about 1.5 turns out and I'm at about 3800 ft and weather is about 75F. Thanks for the help!
Ensure your Gas cap and breather tube are flowing free - if it does not breath in it will restrict gas to float valve - if it does not breath out the tank will build pressure and overwhelm the float valve causeing too high of a fuel level in the float bowl (this sounds like it since the bike does good for the first lap and causes problems on additional laps). Sometimes those one way anodized/bling dohickies that are put on the gas cap cause this problem.... I run straight vent hoses- but the "free flow" vent tubes with "no slop valve" seem to work too- at least when new...
Thanks! And to clarify, it isn't just a minor annoying sputter, it gets to the point that it runs so poorly that I don't feel safe riding it on the MX track for fear it will bog at the wrong time and come up short on a jump or toss my in the whoops. I do have one of those one way valves so I'll replace with a plain hose and see if that fixes it.
Thanks! And to clarify, it isn't just a minor annoying sputter, it gets to the point that it runs so poorly that I don't feel safe riding it on the MX track for fear it will bog at the wrong time and come up short on a jump or toss my in the whoops. I do have one of those one way valves so I'll replace with a plain hose and see if that fixes it.
So I tried a few more things and found that lowing the float height helped a ton! I'm not sure what exactly it should be set at and for that matter, how exactly to measure it, but I made a change and low and behold, she ran real nice! I still need to really ride it hard for a session to confirm the problem has gone away but all signs point to big improvement.
9mm. Angle carb so that the hinge of the float is angled upward at a ~45' angle- the needle and seat should just touch each other but not close the valve. Now Measure between the base of the carb-(where the float cover seals to the bottom of the carb) to the bottom of the Float- which you have pointed upward. That measurement should be 9mm based on what Kehlin says- I'd say no more but could try 9-7mm Sounds like you were a bit high. there's also a rough check with the carb still on the bike-by moving the float drain hose along side the base of the carb where the float bowl is and unscrewing the drain with the hose pointed up towards the seat- the level of the gasoline will show the level of the float if you have the hose positioned against the float bowl. Now mark that level on the carb- and measure between the mating surface(seal) of the carb to float bowl to the mark- should be 9mm... too high causes rich condition if you were jetted for a lower position and its not too far off. Reverse for too low. Too far off and it just does not work as intended. The main reason for 9mm is its within the range of the function required and also to create some consistancy. I'd measure it so you know where its at- but if it is running great- leave it- you may have it in spec again- or just slightly lower- causing a bit leaner mixture throughout. But if you are happy- this may be ideal for you- measure it and write it doun.
