1988 xc250 hydro locking

Hey all! Been a while since I popped in, been working on my newest "resto" which is the loved and loathed 1984 Yamaha IT490.

Anyways, left the fuel valve in my XC on for a few days and went to kick it and it was locked solid. Pulled the plug when flipped the bike upside down and drained it out. Fired right up afterwards.

What's going on here? I pulled the carb for cleaning today but it was clean as could be. Checked to make sure the floats are floating as well and they seem to be fine. Anyone have the height specs off hand?

Also anyone got a spare airbox kicking around? I need the retaining rod and they don't pop up on eBay too often. Also could use the outer cover as mine has a few missing sections.

float valve isnt sealing..you are correct in that dirt can cause it, but it could be worn. should able to set float so its parallel with carb turned upside down.. this is a keihin but will give you an idea

I did flip it over and checked the float arm and it was a little high so I bent the tang down to be parallel with the bowl sealing flange as I have read that's pretty much what you want. Was just curious as usually there's a measurement for it.

If anything the sealing end of the needle and the brass seat looked unworn, almost like they haven't touched in awhile.

ive polished the seat with a qtip and the needle tip to make to make sure they are clean..but something is making that thing not seal..
need to turn off gas everytime you are done riding it, but bike "should" be ok with not doing it.

check the needle and seat on your carb
had that happen and was needle worn out
PM me for airbox

put a NEW CLEAN fuel line on the carb
with the bowl off and blowing gently into the hose slowly roll the carb upside down and see if it really turn off the flow and at what point

really the ony way to tell for sure..doing the "bench test"

my 400 does that all the time if I leave the gas on but doesn't lock, just fills up and you need to kick with full throttle to get a fire going then it shoots all the fuel out the back. could end badly one day

some carbs have a press in or screw in brass seat that can leak between the seat body and the body of the carb, would also check to make sure the floats don't touch the carb internals stopping the needle seating.

Same here John. I just got in the habit of turning the fuel off when I kill the motor.