Husqvarna 562xp cylinder & piston troubleshooting

[preacher31]

Hi all,

FIrst, I'll tell you that I a complete newbie to chainsaw repair. I use chainsaws a lot, but have never disassembled and attempted to repair one until now. I have a 562XP that has run well until now. Over the last couple of weeks, I noticed that it was hard to start (by that I mean that it would turn over, but wouldn't start with many pulls) and once started, would cut off frequently at idle. Last weekend, the saw cut off during idle, so I went to lunch. When I came back and attempted to start it, it was clear that there was no compression. Could pull the starter with two fingers.

So, I decided this was a good time to learn. After reading a bit on this forum and a couple of others, I bought a compression tester. Could only get max 10psi with any number of pulls on the starter. Unfortunately, I did not leak test it before disassembling, so I don't have that information.

In the photos, I've included that crankcase, piston, and cylinder. Ignore the shiny, bad scoring on the top of the cylinder and at the exhaust port. That was my doing during disassembly. Part of my learning and lesson learned. I run 50:1 fuel/oil mixture and you can see oil on the parts. I haven't run it without oil. You can see severe scoring on the piston on the exhaust side and, essentially, none on the intake side of the piston. I don't know enough to comment on the condition of the cylinder. However, I don't see a glaring reason for the sudden loss of compression. Maybe that's because I'm a newbie and one of you will see it immediately and can help me.

Appreciate any help you can offer.

Exhaust side scoring...


Intake side (before and after cleaning)

Crankcase area...


Cylinder...

 

[preacher31]

Here's better cylinder pics...

 

[EFSM]

It may have a bad crankcase bearing or seal or both, allowing it to scavenge maverick air. Or it could be a fuel delivery issue, like bad carb components or fuel line.

 

[beaglebriar]

The cause would have been easier to pinpoint if you had done a leak down test prior to tearing it apart. That said, more than likely your crank bearings shìt the bed.

 

[huskihl]

See if the crank wiggles up and down indicating bad bearings. And if not, do a pressure/vacuum test to confirm if it’s sucking air

 

[preacher31]

Thanks, everyone, for the quick responses. I tried to wiggle the crank and it feels solid. No wiggle at all. I've attached a pic of the crankshaft. It does have about 1/8" of left-right play on this bearing, but I assume that's normal. If not, please let me know. The saw is only two years old and I'm just a weekend property cleaner upper, so no major use. I'd say I've put 15-20 tanks of gas through it, so would hope the bearings aren't worn out yet.

Two questions for you based on your experience:
1) If you were at this point, what would be your next step to fix this thing? Put it back together and do a leak test to pinpoint/rule out? Rebuild the carb or crankshaft before I do that?
2) About the bad scoring on the exhaust side, I've read here that this typically indicates running too lean (air leak or fuel/air mix). I've also read that some recommend a 40:1 fuel/oil ratio vs. 50:1. What are your thoughts or recommendations in this area? I've badly scored the cylinder and piston during disassembly, so will be replacing them anyway, but would like to prevent what bad stuff I can in the future.

Thanks again for the advice!

 

[EFSM]

so would hope the bearings aren't worn out yet.

The bearings on these don't really wear out--the ball retainer fails. It is plastic and can disintegrate, allowing the balls to gather at one side and cause the crankshaft to become out of center.

 

[beaglebriar]

The big end bearing looks very dry. You really should do a leak down test before going any further. 40:1 is your friend.

 

[hacskaroly]

However, I don't see a glaring reason for the sudden loss of compression. Maybe that's because I'm a newbie and one of you will see it immediately and can help me.

Hello @preacher31, welcome to the forums!! The 562 is a nice saw, sorry you are having issues with it! The reason your saw has almost zero compression is due to the scoring. The scoring has forced the ring into its slot in the piston permanently (unless you dig it out) and this is preventing your saw from producing any compression. The ring should spring out, you should need to compress the spring to get it into the cylinder, this ones looks like it would slip in and out without any effort to compress it.


The reason for the scoring is the next step. As stated in above posts, a leak down test will be very helpful. Some other questions about use that may help.

1. When you start your saw (under normal conditions), do you let it warm up for a minute or more or just start digging into a cut?
2. When you finish cutting, do you let your saw idle for a minute or more before shutting it down or just immediately shut it down when done cutting?
3. When you store your saw, do you leave tension on your chain (normal use tension)?

One possibility for the exhaust side scoring (if not an air leak as suggested by oil seals or bearings) could be from immediately starting the saw and digging into your cuts. This can allow for uneven heating up of the piston and cylinder causing the exhaust side of the piston to expand faster and rubbing against the cylinder. This can build up over several uses if the saw is used in this way. Allowing a saw to warm up before using, helps the piston and cylinder to evenly heat up.

Letting a saw idle after cutting before shutting the saw off again helps with the saw to dissipate excess heat and allows the saw to more evenly cool down.

When storing the saw, without taking tension out of your chain especially after using it, the chain as it cools will shrink a little. When it does this, it pulls against the sprocket of the bar tip and the clutch sprocket. Depending on how much tension, it is possible for it to pull on the crankshaft, possibly creating a slight gap between the oil seal and the crankshaft.

 

[big_eddy]

Am I the only one looking at the top edge of the exhaust side of the piston, and the exhaust port in the cylinder and thinking foreign object? Unless that was disassembly damage.

 

[Outback]

When it over heated it ate the top exhaust side of the piston. You can see a chunk gone from the area above the piston ring. Its a pile of aluminum at the top of the exhaust port.

 

[huskihl]

The scoring on the intake side resembles straight gas damage. Usually a lean score only scores the exhaust side

 

[preacher31]

Thank you. I appreciate the info. Honestly, I don't warm it up, cool it down, or loosen the chain for storage, but everything you said makes sense and sounds like good practices to start.

I will do the leak test and will post the results once I have the new cylinder and piston replaced.

Thanks again!

 

[hacskaroly]

Unless that was disassembly damage.

I think it was screwdriver damage, if you look at pics inside the cylinder, you will see marks on the top of the exhaust port and in the sparkplug hole, I think a screwdriver was forced down in there (just a guess).

 

[Woodwackr]

Everything looks awfully dry inside to me.
It will be interesting to see if that cyl can be salvaged, but, that big chunk out of the ex port looks iffy.

 

[FederalQ]

Take a look at the clutch to see if that is blue in color. If it is on a 5 series that could indicate the plastic is melted on that side bearing. They do not tolerate dull chains. These saws run hot as a pistol to begin with. Also pump gas mixed fuel probably becomes stale in 3-4 weeks. All the best!