Yamaha exciter runs fine then starts bogging out

Make sure that the fuel lines and filter are clean and unobstructed

you probley have a weak coil it has enough power to start and run at low speeds but at high speeds the coil does not put out enough spark

Check for venting problems in the fuel tank. Is there a small screw on the filler cap that has to be unscrewed to let the air in when running

Hi, most likely cause and the easiest to check is exhaust leaking in the engine compartment. Run it without the seat fitted for the same time frame and if it fixes your problem you are looking for an exhaust leak. Regards Phil.

most likly needs new rings-or bad plug if you are lucky

Im having problems with mine too. It wants to turn over but never completely turns, is there a trick to getting it to turn over. It has compression, timing, the carbs clean and getting gas. I don't know what to do and losing the battle.

cover up the drilled holes this can cause problems, why was a new carb fitted? did the shop have it running?
not likely rings .
check carb for flooding and correct jet sizes.
check safety kill\start\run switch for shorts.

I have the same problems with my 1999 TTR 250, were you able to find out anything?

Walt
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You need a richer mixture than normal in a cold engine. It sounds like your machine is too lean on the idle circuit. Turn the air screw in on each carb to richen it up. Also, verify the choke is working properly.