Author Topic: Stihl 025 pulled fine with spark plug removed but impossible with it installed  (Read 442 times)

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Offline frypanjack

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Hi All,

    Surely someone else has seen this ? This is 21 years old and doesn't owe me a penny but I'd like to play with it and get it going again. I have soaked the combustion chamber with Sea Foam but with no improvement. I see only a slight darkening on top of the piston while looking through the spark plug hole. Perhaps there is a carbon build up at the top of the chamber that I can't see ? Might this up the compression making the pulling impossible with the spark plug in ? Anybody have thoughts on this ?

Thanks all,
FPJ

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Offline 660magnum

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BTW - Welcome to chainsaw repair.

Don't forget, the problem may be in your starter? The pulley could be split or have the wrong size rope.

I have a 025 from 1993 and the plastic pulley stud in the starter cover was small and someone put a new pulley on it. The new pulley would bind up sometimes when you tried to start it. Sound like someone shot a 22 rifle once when I tried to start it and the pawl broke. That's when I found the mismatch. I found a new MS 250 take off complete starter for it.
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Offline frypanjack

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Interesting idea, thanks for that.

I am about ready to tear it down and will certainly check the starter. I have read that problems like this may be one of more bearings. Strange eh ?

Thanks,
FPJ

Online 3000 FPS

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Try a shorter plug while your at it.
PP 505, 475, 445.

Offline 660magnum

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If the cage goes in a crank bearing, the balls can get on one side and cause the crank to bind. But if your bearing is that bad, the seals are going to be even worse and it will not run. Besides, all those cage parts go up through the engine and ruin everything.

The bearings in a 025 are a very common size and available at most any bearing store.
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Online 3000 FPS

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Pull the starter off and trying turning it over real slow by hand with the flywheel and  the spark plug in.   

 Also if the cage in the bearing are like 660magnum suggests then you can sometimes feel movement in the crank because of it.   
PP 505, 475, 445.

Offline frypanjack

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Great ideas guys. I look forward to some more looking into this this weekend or next.

Many thanks !
FPJ

Offline jmester

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Did you dump the extra sea foam out of the combustion chamber. They can hydra lock
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Offline frypanjack

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Good point, yes I did empty the Sea Foam out.

Offline riverguy

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Hi All,

    Surely someone else has seen this ? This is 21 years old and doesn't owe me a penny but I'd like to play with it and get it going again. I have soaked the combustion chamber with Sea Foam but with no improvement. I see only a slight darkening on top of the piston while looking through the spark plug hole. Perhaps there is a carbon build up at the top of the chamber that I can't see ? Might this up the compression making the pulling impossible with the spark plug in ? Anybody have thoughts on this ?

Thanks all,
FPJ


Did you ever find the solution to this thing?  I just posted the same question but with an 031, also 20 years old.  Some replies said it might be the starter, but yours, like mine, seems to turn over fine with the sparkplug removed.  Seems that would indicate the starter is OK.  I'm a veteran engine builder but know nothing about two-strokes.  This is a mystery!

Thanks,

riverguy

 

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