MS250, not sure whats wrong!

Hi all,

I have a ms250 but it aint running too good when started.

If its cold, when you start it, it takes a while to cough/bite, once it finally starts as soon as you give it any revs it boggs out (even if your really gentle).

if you get it revving and warm it up a bit, its only a matter of time (bout 30secs) when ticking over it boggs out again. And will bogg out if you give it more than half revs..

after it boggs it takes another 10 pulls or so to get it started again.

I have cleaned out the air filter and no change. Have changed the fuel and oil still no change. cleaned the clutch and yet still no change.

Please help me, if you have any ideas on what it could be.

I might just send it in for a survice.

Thanks alot guys.

Poor compression or fuel starvation. When was the last time it was used and was it running correctly then?

Could be a carb setting problem . Spud is yer man ! Ask him .

Its likely to be too little fuel, or too much air.

I had a Dolmar PS34 yesterday with exactly the same symptons. A good carb overhaul sorted that one out.

It had not been used for a while and the solids from stale fuel had choked the carb.

If your confident enough, take it apart and check the inpulse line, inlet manifold and fuel line. Sounds to me like you have a hole in one of them, if you are unsure take it for a professional to look at.

I would clean the breather, give the carb a strip and clean, take a look at the gauze filter and clean if there is crap in it. You may have an air leak in your inlet boot etc. Worth also checking fuel lines and fuel filter.

thanks for the replys guys, they are most helpful, i think i will just take it to the pros to fix i know a guy who might do it cheap for me.

it hasn't been used running for a while, bout 2/3 months.

how tricky is it to take apart and clean???

First thing I do with most saws is to check the compression on the recoil and then with the gauge. Followed by pulling the muffler for a look at the piston. If you have 140psi+ and the piston front looks clean of scoring then there is little reason to strip it down.

I then Vac and pressure check the engine - this is a bit advanced and you need specialist kit to do this but on the positive side, it will tell you if you have leakage in the crankcase, impulse line and carb boot.

If you can't do the above then you have to use visual inspection and it is far less reliable.

Carbs are easy to strip down but there again I have done hundreds and know EXACTLY how they work - checking the gauze filter is pretty simple though - it is under the cover with the single retaining screw.

The actual engine on a MS250 is a clam style engine and IMO isn't the most easy of engines to work on as you have to pull the complete assembly out of the plastic cradle to work on the cylinder/piston. Vertically split crankcases are 1000 times easier.

If the above means nothing to you - give up and take it to someone who knows their craft - I do take on problem saws but if you have a local guy, try him first and ask him if he can do the above:thumbup:

Carbs are easy to strip down but there again I have done hundreds and know EXACTLY how they work

That's quite a statement...

3 simple questions for you then, the carb is from a 1122 series Stihl;

-What is circled red and what is its purpose?

-What is circled blue and what is its purpose?

-Is the idle system dependent or independent of the main jet system?

That's quite a statement...

 

3 simple questions for you then, the carb is from a 1122 series Stihl;

 

-What is circled red and what is its purpose?

-What is circled blue and what is its purpose?

-Is the idle system dependent or independent of the main jet system?

Not sure how this helps the guy fix his saw as the point I was making was that I can coinfidently strip and set up a carb but he may not but anyway: -

Blue - full load semi fixed jet for high speed running

Red - Part load valve jet - controls low speed running and has a built in one way valve to stop pressure changes in the carb throat effecting the fuel in the diaphragm part of the carb.

The carb is dependent on the main jet

Do I get a teddy bear/goldfish etc:lol: