Trying to get an old 60's Stihl 08S working

[amfell]

are you starting the saw with the top on ?

 

make sure that the throttle linkage wire is working the throttle shaft it can miss when re-assembling

 

is the choke slider knocking the choke off ? it can stick the choke flap on ( some have a horseshoe shaped wire that knocks the choke off )

 

it's easy to check the above by viewing down carb when the airfilter is removed

[Huskyswinger]

The linkages are all correctly located and the mixture is set at 1 turn out.

I also replaced the fuel hose.

 

Even when the engine is running adjusting the mixture screws makes no difference at all which is odd as I've worked on saws before where it's a case of just adjusting the mixture but this is being a right bastard :-/

 

So to summarise:

got a decent spark

Compression reads about 105PSI

new diaphrams and gaskets on carb

adjusting mixture screws makes no difference at all

new fuel pipe

only can manage to get to idle with the trigger lock on locking the throttle to half position - even then its a rough idle and will not rev.

[Rich2484]

Crank seals then. Only thing is an air leak in the crank case causing it to run rich. This would also be why adjusting the carb isn't doing anything. As no matter how much you adjust it it won't get the right mix with the air.

 

Running on half throttle is enough to get just enough fuel to air mix, but not for long.

 

Best to get it pressure and vac tested.

[Eddy_t]

Your compression is really low mate!

 

 

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[Highrigger]

Re ring it and do the crank seals compression should be about 150 . Could have a seized piston ring, so it is not getting compression , scuff the cylinder wall with some 220 or muriatic acid.

[MATTMOSS]

Crank seals then. Only thing is an air leak in the crank case causing it to run rich. This would also be why adjusting the carb isn't doing anything. As no matter how much you adjust it it won't get the right mix with the air.

 

Running on half throttle is enough to get just enough fuel to air mix, but not for long.

 

Best to get it pressure and vac tested.

 

Wouldn't that cause it to run lean?

[Rich2484]

Wouldn't that cause it to run lean?

 

very true. my bad.

 

but would still explain the rough running problems.

 

the compression imo is fine. 150 is about right for a second hand saw. it should run fine on this. have you done a compression test after it has been run up and warm?

[MATTMOSS]

very true. my bad.

 

but would still explain the rough running problems.

 

the compression imo is fine. 150 is about right for a second hand saw. it should run fine on this. have you done a compression test after it has been run up and warm?

 

Ok im just here to correct you

He says the compression is 105 not 150 so it is low

as you were

[Rich2484]

Ok im just here to correct you

He says the compression is 105 not 150 so it is low

as you were

 

thats it then. i give up. im going to bow out gracefully now.... :001_tt2::lol:

[Huskyswinger]

I should have said also it was apparently running fine before being put into storage...

 

Will look into crankcase pressure and rings though

 

Thanks.