Hoping for some help,my in-laws 250 with Mikuni carb has problems.Think it is a 03 2wd.He bought new,has had no problems.He rode it last month and it filled crankcase up with gas.not sure if it was on run,or prime on petcock.He installed a shut-off in line,to keep from filling crankcase again.I told him float needle valve was probally bad.
He had my son put a Suzuki kit in carb.I don`t know how it was running at the time kit was put in.
We have the idle adj turned all way up now.
Air adj screw is about 1.5 turns out as was original.When you start it now,you have to put it on prime&choke.It runs very fast for aprox 2 minutes,then acts like it`s starving for gas,all of a sudden.Hard to keep running,you have to put it back on prime&choke again &give a lotta throttle to keep it running.
I had my son clean carb again,cause I pulled gas line off and saw some black bits coming thru hose.I also had him clean&flush tank,and he said it had a lotta crap in it.We also put on new clear fuel line&he again cleaned carb.He said he blew air thru all ports.
I haven`t had carb apart myself.If you turn air screw 3-4 turns out,it will run better,but won`t start.
I`m not familiar with the Suzuki petcock,as I only had Hondas in the past.It has some kinda vacum line from top front of carb to right side of pet ****.I can only assume that is some kinda safety deal that only lets gas thru if engine is running for tip-overs.But you can pull gas line off carb while in on position,and the gas runs out of tank?
I don`t want to tear into carb,since I didn`t do it before it was messed with,without some new ideas.

I`m thinking maybe a port,or passage in carb need a wire ran thru it,or maybe a float height issue.
Any ideas on this long story please?
Thanks,Dizz

 

Could the fuel tank vent be clogged? The vacuum line to the petcock goes to a diaphram that shuts of fuel when the engine is off but they can still let fuel through. On older models the air screw setting is 2 3/4. I will check my book tomorrow.

 

I have a 97 LT-F250 thats doing the same thing. All ready replaced the petcock and rebuilt the carb. It runs good till it gets hot then dies and is hard to crank. I have the adjustment screw about 1 3/4 out. Does anyone know what the clearence should be on the valves?