250-500cc WR 250 is bogging down and shuts off after a minute

I recently picked up a 2010 WR 250 from a local dealer, the bike had been used but the engine is all redone. The bike starts up perfect and runs amazing for about 1 minute then darts to big down until it cuts off. I tried changing the plugs and same thing. It can idle forever but ad soon as I get on it and go it lasts about a minute. Also blows a little bit of white smoke. I don't want to start screwing around with anything until I get some input from some people that know what they are talking about.. Thanks!

Maybe fuel supply is restricted and not supplying the carb bowl fast enough. I would start by checking float level and needle valve as well as petcock in the tank.

White smoke after it heats up? check your radiator level.sounds like it could be a head gasket issue.They could have reused the head o rings? What does your plug look like? pics would be great to help you out.

Thanks for the replies everyone! I'll have a look in the morning and let you know what I find.

If the pet-cock is not flowing enough fuel,remove the pet-cock and inspect the gauze filter screen. I had one plug up on a previous bike I owned and it ended up in a piston seizure! I remove the filters on all the pet-cocks on my bikes and run an in-line filter.The in-line filters are cheap and are easily inspected to see when they are dirty! Also check that the gas cap vent is clear and allowing air to flow into the fuel tank.

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maybe its sucking gearbox oil into bottom end

Gear oil would blue ish smoke and wont stop it running ! sounds like the tank is not venting to me and or as stated blocked filter / gauze, Have you looked at the coolent level ? just in case its sucking water