Any chainsaw guys here?

[Shannonwilkerson]

Hey guys.
Let me preface this with: I’ve been through automotive engines successfully, but this it my first little bitty chainsaw engine too end job.

Machine in question is an old Husqvarna rancher 55. It came to me with a no start. Found out it had 30 psi of compression.

Took it apart and found a little burnt spot on the ring-land that was causing the piston ring to stick, so I think “cool, I’ll just put a piston kit in it.”

BUT I would appreciate a few dozen opinions on the cylinder first. Would you reuse it?

-I don’t feel any of the scuffs with a fingernail or my fingertip-skin.
-no “ring ridge” top or bottom of stroke.
-the crank bearings feel ok
-big end of rod feels ok
-The burnt spot on the ring land was not on the intake or exhaust side. It was sorta in between. Very small spot.

Keep in mind this appears to be the original cylinder. Or at least an oem replacement.

 

[SC Maintenance]

Doesn't appear to be a ridge at all, so I for sure would try it.

How much compression is a little 2-stroke supposed to have?

 

[spasm3]

Just me, but i would get a matched piston and cylinder set. So the piston to wall clearance would match better.

 

[Shannonwilkerson]

Doesn't appear to be a ridge at all, so I for sure would try it.

How much compression is a little 2-stroke supposed to have?

Judging by the other forums I’ve lurked on, most people like to see around 150 psi.

 

[wavinwayne]

..How much compression is a little 2-stroke supposed to have?

At least 100 PSI for ~30-40cc saws, up to 160 PSI or more for 60cc+ saws.

 

[Japanese]

BUT I would appreciate a few dozen opinions on the cylinder first. Would you reuse it?

Looking at those pictures - the cylinder looks fine.

Did you put the new rings in it and measured the gap? I don't know about chainsaw's cylinder, but on 2-stroke bikes the ring gap should be about 0.3 mm (.012"-.013"). If the cylinder is worn out the ring gap will be more than that.
However, chainsaws rings might have smaller gap because they have smaller displacement than bikes. So it should be around 0.2 mm (.008").

You can also compare the gap of the old vs the new ring. If you install the new rings and you get the desired PSI, then you don't have anything to worry about.

 

[grasscutter]

-the crank bearings feel ok

What about the crank seals? On 2-cycle engines, leaky crank seals will cause all kinds of problems.

Usually the first troubleshoot procedure is a pressure / vac test.

Put the whole crankcase under vacuum.

Apply 2-cycle oil to the crank seals.

If the oil gets sucked in around the seals, replace the seals.

 

[Opelman]

I can't add much to the good advice given already except to avoid the dirt cheap aftermarket parts. We use Meteor from Italy for Stihl top ends as OE is killer expensive if even available. Husqvarna OE is much more reasonably priced, go factory if it's available.

 

[ironman_gq]

cotton swab and muriatic acid, wipe down the streaks and see if they clean up. If you can't feel them I'd stick a new piston in it and see how it runs. Check the crank seals and intake boot for leaks and send it on it's way. It's an old very common saw and not worth putting too much money into it. If it's going to be used for more than occassional cleanup I would put a good quality piston in it though, meteor is a good brand, should be $30-40. Compared to some of the saws I've seen that cylinder does not look too bad, most of those streaks are just burnishing of the nikasil coating. They don't really wear at all till the coating fails then it's time for a new jug.

 

[tnt_motorsports]

I would reuse that cylinder without a doubt if you can't feel the scratches. FWIW, I've used mild Scotch Brite with engine on cylinders like this in the past just to clean them up. DON'T clean up and down, go around / cross method best you can. Clean very well with brake cleaner or engine degreaser after.

 

[ccs368]

I have serviced my 017 Stihl chainsaw and replaced rings as well and the crank seal is indeed important for proper operation as I’m sure everyone knows with 2 strokes. However, I would have slowly pulled the cord prior to disassembly and feel the resistance thus giving you an indication of sufficient pressure. The cord should fight you almost pulling the power head away. Unless the chainsaw was abused with improper 2 cycle oil mix and you see scoring on the piston skirt and corresponding scratches in the cylinder wall, usually hard starts is carb related. Check spark plug by grounding the plug on the cylinder and see if you get spark. Confirm compression by feeling the resistance of the pull cord. See if spark arrestor screen is carbonized with soot. Then the last thing is fuel delivery with carb cleaning which is another topic