I rebuilt the carburator on my f-250 ..400m...went perfect ,runs great...then I tried the same on my mid 90's 440evl echo chainsaw.
disaster...it keeps fooling me . it has behaved as though it is fixed but then goes back to the same problem.. I NEED TO TALK ...PLEASE long story short, it only runs at high speed, has slow responce to triger (gas) and won't idle..like I say it would act fixed for 15 min then go wild again.

 

Sometimes you need to check for things its not..

Like, what the compression is/isn't. If the compression is low, it will have a terrible bottom end, unstable idle and a poor throttle response. Also, if the crank shaft seals are leaking it will create a bad lean condition at low RPM's. Also, make sure the carb diaphram is set at the correct level to the carb base/body. Reed valves were replaced?, should have been if it was a full kit rebuild.. Fuel tank is venting OK? Does the carb 'respond 'to H&L range adjustments. Especially Low range. Throttle shaft/bore has no excessive wear?

 

all great info , thanks much, It was not a complete kit. I got high and low speed needle screws , both diaphrams ,(fuel pump and metering),and gaskets . I will check compression and start looking at leaks etc. away from the carburator. Thanks again. I will defenately let you know how it went.
Oh also i lost the gas cap along time ago and am useing a plastic cap off a jug that fits tight with no vent . But I have been using it for couple years and this problem is pretty new.