Weird MS251C Starting Problem

[Wood Doctor]

OK, I seldom run into this with a new Stihl chainsaw, but I have a real problem with an MS251C. It has the new pull cord start assist mechanism that drives me a bit crazy. Regardless, this saw refuses to start using the typical procedure discussed in the Operator's Manual. I doubt the saw has 5 hours of run time under its belt. The owner, who died suddenly of a heart attack, bought it from a dealer, paid 400 clams, owned it a year or so, paid another 50 bucks to have it serviced, and it still will not start, run, or idle normally. In short, it's an expensive dud.

The only way I an start it after a choke pull and a few fast idle pulls is to next pull it at WOT a few times to clean out a flooded engine. Then it will blow fuel and smoke out the exhaust for awhile, but dies trying to idle. At that point, it's a dead puppy again with a fuel-soaked plug. The $50 servicing charge by the dealer that the late owner paid for was to install a new plug, add fresh fuel, and adjust carb. That failed miserably.

Any suggestions? I'm all ears and TIA.

 

[drf256]

Toss another carb on it. Disable the primer bulb if so equipt. Try it again.

I'm not sure if the 251 is a glorified MS250 or a totally different model. If it's the same as the 250, you can get a Chinese replacement carb for <$15 delivered to your door from amazon.

 

[a. palmer jr.]

I've had to replace a lot of carbs on those smaller Stihl saws. One thing I can say for sure is don't run ethanol fuel in them! The dealership repair guy probably should have run a pressure/vacuum test on it also..

 

[sawmikaze]

A guy i know had a 251 that drove him nuts with similar symptoms , a new carb cured it .. they are a totally different saw from a 250..not bad when they run right.

 

[Simondo]

Sounds like the classic metering needle /leaver /diaphragm situation and or combined with carb H ,L adjustment issues . Many and varied reasons but its flooding out...first port of call is the metering side.

 

[Wood Doctor]

Great posts from all of you. Here is my "fix" because I think other buyers of the Stihl 251C have run into this instant flood problem. I pull on choke only once after a prime. I don''t wait for a pop with more choke pulls because that won't happen and you will flood this engine. Move to fast idle immediately for the second or third cold-engine pull. Saw will probably start.

After that, I patiently tuned the carb for optimal performance, shut it off, and it started again on the first fast-idle pull. I'll see if it acts the same way tomorrow. Hard to believe that two choke pulls would flood an engine completely and no fast idle pulls would unflood it, but that's what I ran into with an almost-new saw.

I agree with Simondo that it's the metering side of the carb that is causing it, but why this would happen on an almost new engine is really hard to believe.