Bikes begging and losing power in 4th

[Randall]

Yamaha dt125r 2001 7k miles just had a top end rebuild by Yamaha... has been run in efficient but this morning on the way in from work 4th gear it started to loose power and begin to hold back as if its bogging. Change down into 3rd or 5th and its runs fine and wants to go all through the power band. Any idea on what to check or look for.

[Calum]

2001's were the worst for the restrictions

Reed Switch done? Powervalve pinned? Aftermarket exhaust?

The higher the gear the more load there will be on the engine. You will want to make sure that the fueling is sweet, it will become more prominent in the higher gears as to whether or not the fueling is setup properly.

[Randall]

@Calum the power valve was working fine before the rebuild .. the red switch was located at the back of the clocks and taped up with vaseline at to stop it getting wet. I've got a full depth system which is not on as its winter and their prone to rotting out... carb was set up correctly and fuel is fine been working fine all but this .. 75/80mph with the standard pipe derestricted power valve is not pinned though but is working fine

[Calum]

@jamesrandall93 Check fueling and spark then. Could be the colder weather affecting your fueling. Could be ignition system breaking down.

[donaldmendez]

@randall Did you fixed this? It's odd but I experienced this on mine too. Engine is bogging down when I give it a full throttle. I checked the ful and spark but they seems normal.