Hi hope soneone can help my dt250 mx revs up fine when in nutural but as soon a i put it in gear and  start of  it will not rev up above 2000 revvs and just bogs down

Hi & welcome from NZ downunder. I can only guess without having video which is always helpful. My only guess at the moment is a very blocked up exhaust in the tail muffer & deeper in there where there should be a spark arrestor which should be spot welded in so burning the muffler in the log fire would fix it. I'm guessing at that & thinking it would free rev to a point but i doubt it'd get very high unloaded if it will only pull 2 grand in gear riding it. So on the face of i could be quite wrong. An easy quick test would be to remove the muffler & give it a try to prove a point. It could be blocked up further in so look in the end of the main pipe where the muffler slides in as can build up where the muffler pipe finishes. See if you can do a video to link through youtube or similar.

Please supply some history. Was the bike sitting for a long time, or was it running fine, then the problem started? How old is the fuel and do you have an inline fuel filter and if so, does it appear to be flowing properly? What's the state of the carb, have you had it apart and checked for varnish/gum and that the gaskets/o-rings are good? Is the float height set correctly? Spark plug looks good and spark is bright? Air filter not clogged or over oiled? RT325's note about the exhaust is a good point to start.