YZ 250f loss of throttle?

[Ross chan]

When I start my bike and pull on the throttle slowly to moderately it revs fine but when i go to grab a fist full of throttle it seem to dog out by almost dying like a bogging noise. When riding for a bit the bike takes more effert to get started. Any help would be great thanks in advance. YZ 250 Rider!

[642MX]

Sounds like its time for some jetting changes. https://www.thumpertalk.com/forum/showthread.php?t=311954

[av]

Check your jetting but the problem you're describing is the famous "bog" problem these 4 strokes have. Do a search on "bog" and you can read for days.

Bottom line, make sure your jetting is correct, check the AP circuit and squirt timing and use the appropriate leak jet and you should be able to fix the bog. Read www.thumperfaq.com - lots of info there.

[brob01]

Had the same problem when I blew my engine. Not saying it's anything big like that but just make sure you have enough coolant in there and make sure your water pump is working right.