Stihl 064 Troubleshooting

[Flint]

Bought an old Stihl 064 before all this lockdown process began in the hope of using it as a small milling saw, and finally now getting around to getting it sorted out. Know these aren't the bombproof powerhouses that old 066 or 088s are, but hoped it'd have enough grunt to pull a 25" lo-pro bar on a granberg style mill?

 

Saw is in good condition, fires up first time, but has a couple issues & I could use some guidance as to where to start first with repairs/troubleshooting. 

 

Starts easy & on first pull, cuts well with plenty power & comes to speed nicely, and idles whilst held, no excessive smoke etc. Moment I put it down whilst idling, it cuts out dead- doesn't stall or struggle first, just completely stops dead. Is this likely a wiring fault and saw is earthing when put down? If so, where to look for issue? Coil?

 

Once hot, saw chain is running on and starting to race the revs- presumably a carb tuning issue, but could this also be an air leak? any way to narrow this down without pressure/vacuum testing? Happy to replace seals/hoses & rebuild to fix common culprits, but would like to know where to start- fuel line, impulse line, gaskets etc?

 

No obvious issues with compression (has loads), and piston looks good condition with no scoring visible from exhaust ports. Already cleaned out air filters, replaced fuel filters etc & fresh mix in tank. Any pointers from old saw gurus on where to start?

[spudulike]

It could be the low screw is a little lean but it could also be an air leak. If you are good at setting carbs then you can often tell if a saw has an air leak but if you haven't tuned saws daily then it is more difficult.

The L screw should be 1 to 1&1/4 turns out, if the low screw is on this setting and your saw is racing like this then I would get it pressure and vacuum tested as the next thing to happen may be a seize and that isn't good.

Air leak issues may be seals, impulse line, manifold issue/split or gasket issues.....you sometimes get a loose or cracked cylinder but it is rarer.

If it was my saw............

[Flint]

Thanks Spud, will try the carb settings on Friday when I've got some time to play with it. May see if I can do the impulse line & some of the usual suspects too, carb clean etc if I get the time. 

 

If I have no luck with it, might be sending it your way- have had the pleasure of using a spud-modded 372xp in the past that was an animal of a saw, & curious to see what you could do to a 064!

[spudulike]

I got a friend a very clean one, it was ported and is his go to saw...one he will never part with...must have been good!