[rbm33]

have an 05 250r that is having some carburator issues.

the bike completly falls on its face when the carb is just cracked open, if you hold it cracked open while just cruising down the trail it will miss so bad that that it will eventually die. when the throttle is held open it runs pretty good, maybe not perfect but a lot better than it does at 1/8 throttle.

the carb was jetted properly and running fine, but we sent the engine out for a new crank and they also installed an AP mod on the carb. when we installed the engine we noticed the obvious miss.

the shop says they never touched the carb other than the AP mod.

sooooo, here is the list of things that we have checked and tried......

changed air filter

verified that jetting has not been changed. jd kit with red needle at the 5th groove, 175 main, 42 pilot fuel screw at 1 3/4 turns.

cleaned jets

removed AP mod

verified that cover on slide was not upside down

checked float height 8-9 mm

changed spark plug

changed fuel

cleaned carb again, tearing down to bare casting

unplugged tps


finally we installed another carb from another bike and it ran great, so basically all we know at this point is that it is from the carb. we know it ran fine before the engine went to the shop and the jetting hasnt been changed from the jetting that has been installed for the last 2 years.

any ideas on what we have missed??? again the carb was fine before the engine was pulled out for a month.

[marks crf]

try a power valve for the carb
or go on ebay mate they got really cheap crf250r parts like carburettors

[JamesDean]

Just to be sure, the thin plate on the carb slide must be installed with the hole near the bottom and the square end down. Make sure there are no air leaks and that the choke is closing completely and is not bent or damaged. See that the vent lines are clear and the float level is correct. Check the fuel supply and that the fuel flows freely both out of the fuel line and thru the carb and out the drain.

See the carb slide below-