Stihl ms 250 won't re-start

[Rowan the Bruce]

Hi guys I have this problem with the ms 250, it struggles to start after it has been running and warmed up switch it off and then its either flooding or too lean. Not sure of the problem. Any advice please, today is the first day of not climbing for about a month so may be able to sort it.

[spudulike]

Difficult to get to the route cause without further info but here are a few usual suspects: -

Low compression - when warm, it lowers and stops the saw starting.

Bad coil - plays up when hot (less likely)

Blocked fuel tank breather - undo the fuel cap and put it back on - will the saw start better now.

Dirty carb - crud in the gauze filter

Poorly adjusted carb - is the saw set too rich - causing the flooding

Carb needle valve leaking

Faulty fast run throttle starting mechanism - you can check this by holding the throttle open and trying to start the saw like this - probably a two man job

Loose choke valve - seen this recently - check the tightness of the brass screw that holds the choke valve plate in place

Petrol fuel pipe has gone sguidgy

Petrol pipe is holed

Check the condition and gap of the plug - 25 thou is about normal!

Blocked air filter/fuel filter

There you go - that will keep you busy!

[GardenKit]

There you go - that will keep you busy!

miffed...... because I cant think of anything to add. You should write books:001_cool:

[spudulike]

miffed...... because I cant think of anything to add. You should write books:001_cool:

 

I try to be thorough, it is like anything - just need to get under the skin of the machine and think about the problem. The answer is never far behind:thumbup:

 

Never easy with sketchy details and the machine not in front of you.

 

I am sure your overall knowledge of other garden equipment is far greater than mine will ever be - just specialise in saws but a machine is a machine in my books - just takes a little longer on some!

[GardenKit]

Never easy with sketchy details and the machine not in front of you.

 

 

Sure, and on this MS250 I think we need a bit more input from the OP about its performance prior to the first stop.

 

Does it start normally from cold?

Does it tend to bog down easily?

Does it tick over smoothly without dying?

Does it pick up from tickover without hesitating?

Does it perform normally until that first stop?

Is that first stop intended, or unintended?

 

(just had to add something!)

[pleasant]

Check the condition and gap of the plug - 25 thou is about normal!

 

 

Yup...but I would add that the plug could be breaking down when warm/hot, so the gap and visual inspection would not necessarily rule out a faulty plug. For a fiver I would put a plug in anyway.

[Rowan the Bruce]

Checked the plug and its well blackened so looks rich to me, must've had one of the boys took the old orange screwdriver to it. got a new plug but need to tune it now.

[spudulike]

Checked the plug and its well blackened so looks rich to me, must've had one of the boys took the old orange screwdriver to it. got a new plug but need to tune it now.

 

Well, thats a start, saw overly rich, starts fine when cold and then is too rich for when it is warm/hot:thumbup:

[miker]

a fiver for a plug..??!!

[GardenKit]

a fiver for a plug..??!!

A 'pleasant' surprise???