MS250 Doesn't Like to Rev if Cold

[adamelder]

F***ing bingo!

 

I did what was suggested by you fellas.

 

Gave it three good pulls and it took off like a stabbed rat. And it continues to run fine and dandy.

 

Many thanks for all the help!

 

So when I found it looking very neglected and forlorn, to now - with it's new carb innards, clutch, sprocket, chain, filters and a couple of springs and things -

it's back, howling happily in the land of the living.

[Harry_L]

Yay! Congrats

 

 

Sent from my iPhone using Arbtalk

[bmp01]

So when I found it looking very neglected and forlorn, to now - with it's new carb innards, clutch, sprocket, chain, filters and a couple of springs and things -

it's back, howling happily in the land of the living.

 

Top result, well done ! You'll be out scouting for more "fixer-uppers" next :lol:

 

bmp01

[spudulike]

Group hug:thumbup:

[adamelder]

Well now... I've only run it for a couple of hours since it came to life but unfortunately the old problem has come back.

 

Refuses to rev once it gets hot.

 

Then refuses to start.

 

So I changed the carb for a cheapo import. It ran fine for 20 mins and then started playing up again.

 

Then I changed the impulse line.

 

Same problem again.

 

So that's all fuel lines, carb kit changed but the issue persists... if I can get it to start, it'll run on idle, rev fine and high for a few minutes but then gradually start to not want to rev. Then it stops and won't start.

 

I've checked that the fuel tank is breathing.

 

What next?

[Stubby]

Low compression ? Those are the the symptoms you describe .

[spudulike]

Time to give it to someone who can fix it I think:sneaky2:

[adamelder]

Time to give it to someone who can fix it I think:sneaky2:

 

My thoughts too.

 

Compression is good, spark is fine, piston is unmarked.

 

 

Or considering just skipping it given that I've probably spent towards £100 on it up to now and that it'll be at least that again if it goes in to the Stihl dealer.

 

Having said that I've enjoyed mucking about with it but there are limits to what I know or to be honest, want to know!

[spudulike]

The issues that are generally heat related are low compression - you really need around 150psi+ when cold as it will fall by 10-20psi when hot. Not sure how you are measuring it but do it cold and then hot and let us know the readings.

 

The other one is coil related. Either the coil is breaking down with heat or the gap is too big and as the coil gets warm, the spark weakens/fails. Had a MS460 like that once.

 

It could be a few things but checking the compression and spark when it has died are two logical things to try.

 

The tank breather, if blocked, can cause the saw to die after a few minutes running as a vacuum is produced in the fuel tank as fuel is taken from it and once built up, stops further fuel being pulled through.

 

There does become a time when it is best to get rid, strip for spares, ebay it or get it to someone who may have more luck with it.

[adamelder]

Spud,

 

I'm no mechanic so don't have the gear to measure compression accurately. I do know that I can pick the saw up by the starter without it pulling out when it's hot.

 

I've checked the coil gap and it's business card sized.

 

I can blow through the breather no problem at all.

 

I'm minded now to admit that the saw is beyond my skills to resurrect or uneconomic to get repaired.

 

Like I said earlier I've enjoyed the learning process of stripping the carb etc and putting it back together without making things worse!

 

Anyone want it?