Stihl ms231 hard to pull

[aidank]

I have a Stihl ms231 and it's hard to pull.  I took out the spark plug and it freewheel over.

 

4 5 year old saw not a lot done.  Had carb seals replaced a year ago petrol eats them apparently 

 

Idles perfectly 

 

Starts perfectly it gives its cough after 3 drop starts same as when new.  Flick the choke and then it will start first pull.

 

It was over revving last day I used it so I gave the H screw one turn anticlockwise and going v well now.

 

Any ideas on the hard to pull over

 

 

[Stubby]

37 minutes ago, aidank said:

I have a Stihl ms231 and it's hard to pull.  I took out the spark plug and it freewheel over.

 

4 5 year old saw not a lot done.  Had carb seals replaced a year ago petrol eats them apparently 

 

Idles perfectly 

 

Starts perfectly it gives its cough after 3 drop starts same as when new.  Flick the choke and then it will start first pull.

 

It was over revving last day I used it so I gave the H screw one turn anticlockwise and going v well now.

 

Any ideas on the hard to pull over

 

 

Don't understand re " hard to pull over " Idles perfectly "  If it was over reving maybe an air leak . Might have nipped up ?

[aidank]

21 minutes ago, Stubby said:

Don't understand re " hard to pull over " Idles perfectly "  If it was over reving maybe an air leak . Might have nipped up ?

The pull cord is difficult to pull to get it to start.

 

Its when it gets to top dead center as you are pulling the cord it gets difficult pull the cord, 

[Stubby]

1 minute ago, aidank said:

The pull cord is difficult to pull to get it to start.

 

Its when it gets to top dead center as you are pulling the cord it gets difficult pull the cord, 

Maybe a bit of carbon on the top of the piston connecting with the spark plug ?

[aidank]

2 hours ago, Stubby said:

Maybe a bit of carbon on the top of the piston connecting with the spark plug ?

Sparkplug in perfect condition I had it out earlier 

 

At the start of pull it is easy then compression builds up and it gets v hard. Once over this tight bump, Cycle repeats 3 times approx and cord is fully extended.

[Mark_Skyland]

Is it the c be version with the easy start?

If so check the starter mechanism, its a bit more complicated than standard starters and it might be causing the issue that you have.

 

[pleasant]

By coincidence I had an ms250 (earlier model, but similar) in this week, which customer stated was hard, near impossible to pull over with plug in situ and the rope would 'kick back' out his hand. Difference was to yours is that it wasnt starting at all...otherwise same symptoms.

We took muffler off and clean as a whistle....piston and barrel fine. Removed plug and it would pull over fine. Correct plug fitted btw.

 

Removed recoil assembly. Operating fine. Removed flywheel. Keyway fine.

 

Noticed some oily residue around flywheel area and noted. Refitted flywheel and recoil. Again, pulling over fine with no plug fitted. Decided to do a compression test as we had the plug out. With compression tester fitted it wouldnt pull over.

 

There was the possibility the carb was flooding the crankcase. Machine was tipped upside down onto some blue roll,  with nothing in the plug hole and recoil pulled several times. Blue roll was flooded with fuel despite the plug being quite dry when saw was in the upright position.  This, together with the oily residue around the flywheel pretty much confirmed our suspicions, as the crank pressure whilst trying to pull it over would have allowed excess fuel to blow past the crank seal to a degree.

 

Our final confirmation check was to drain the tank and remove all fuel from the system. We then refitted the plug and it pulled over perfectly. 

 

New carb now on order as customer stated he has rebuilt it twice over the years, and we wanted to guarantee our work, so a new carb was the best option.

 

Yours could be similar. If the needle isnt seating it can supply a constant flow of fuel, much like a dripping ball valve in your toilet cistern.

Edited February 23 by pleasant

[spudulike]

That is a very good call, fluid is near impossible to compress unlike gas (not fuel if you are American).

I could tell you why this is but people do glaze over most of the time😉

The cause will be a leaking needle valve in the carb.

[aidank]

10 hours ago, pleasant said:

By coincidence I had an ms250 (earlier model, but similar) in this week, which customer stated was hard, near impossible to pull over with plug in situ and the rope would 'kick back' out his hand. Difference was to yours is that it wasnt starting at all...otherwise same symptoms.

We took muffler off and clean as a whistle....piston and barrel fine. Removed plug and it would pull over fine. Correct plug fitted btw.

 

Removed recoil assembly. Operating fine. Removed flywheel. Keyway fine.

 

Noticed some oily residue around flywheel area and noted. Refitted flywheel and recoil. Again, pulling over fine with no plug fitted. Decided to do a compression test as we had the plug out. With compression tester fitted it wouldnt pull over.

 

There was the possibility the carb was flooding the crankcase. Machine was tipped upside down onto some blue roll,  with nothing in the plug hole and recoil pulled several times. Blue roll was flooded with fuel despite the plug being quite dry when saw was in the upright position.  This, together with the oily residue around the flywheel pretty much confirmed our suspicions, as the crank pressure whilst trying to pull it over would have allowed excess fuel to blow past the crank seal to a degree.

 

Our final confirmation check was to drain the tank and remove all fuel from the system. We then refitted the plug and it pulled over perfectly. 

 

New carb now on order as customer stated he has rebuilt it twice over the years, and we wanted to guarantee our work, so a new carb was the best option.

 

Yours could be similar. If the needle isnt seating it can supply a constant flow of fuel, much like a dripping ball valve in your toilet cistern.

Some good info there thanks.

 

If carb was leaking as you mention then I think it would never start as you say.  

 

If spark plug gets wet then there is no option but to dry it off.

 

Had that problem and repair shop put in new seals in the carb a year ago or thereabouts. Told us modern petrol eats them.

 

We are starting perfectly saw gives a cough on pull 3 or 4 with choke closed and then open choke and will fire up first pull. That is how it performed when new.

 

Don't have any oily residue around the flywheel had all that exposed yesterday when I was replacing the pull cord 

 

I see carbs on eBay for 15 20 euro are they genuine or worth bothering with 

 

 

Edited February 23 by aidank

[Mark_Skyland]

If the carb is leaking once you fire it up it will pour out smoke and run really rough for a bit.

 

A 15 euro carb is definitely not genuine and its hit and miss if they are any good. Worth it for a last ditch attempt before binning a machine though. Its around £100 for a new carb over here.