How bad is this piston? 550xp Project

mbrick

mbrick

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If the fuel tank was punctured, why is it optional for replacement? Are you going to try and patch it?

As others said the cylinder needs to be removed to evaluate. Some better photos of the piston and overall saw would also help us!
 
Chainsaw Jim

Chainsaw Jim

CJ Saws, LLC
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Thanks for the advice. I'll add those to my list. I take it you would recommend doing both clutch and flywheel sides? I haven't checked yet, but was the 550 the same as the 562 with the series of carbs (EL44/46/48) and one working better than another? If so, I might just throw on a new carb.


Would you have any guesses as to whether it was the fuel mix, the congestion, or the carb itself causing the lean? I wouldn't be surprised if this saw had been run dull quite a bit. The bar that came with it has chunks/divets missing from around where the sprocket inserts. Basically looks like someone took a chisel or jackhammer to it. It even came with a brand new chain! Doesn't look like it's been filed once, little wear on the tangs.
Change both.
I cannot say for sure about the carbs with the 550.
I wouldn't know what the exact problem is without having my hands on it. But in my experience a saw in that condition usually needs all the serviceable/rubber parts changed out.
If it were mine I'd tear it down to the case for a complete inspection and check the torque on the case screws.
 
nwhunter

nwhunter

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I recently went through building an ebay 2012 550xp.
It was very clean but had a smeared piston and broken choke shaft.
It passed vacuum pressure tests and bearings felt good so I didn't replace those.
I bought an new oem piston cylinder for around $125. Piston was unusable and oem piston rings alone were near $100.
I basically gutted the muffler to try to reduce heat, it seems that heat and air leaks are the 5 series saws worst problems.
I have ran the saw for maybe 6 hours over two days clearing, limbing, bucking and it is little screamer.
I have about $250 in this saw and don't regret it, seems to be a nice saw.
Fix it, check pressure and vacuum and you will have an enjoyable saw.
 
HumBurner

HumBurner

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If the fuel tank was punctured, why is it optional for replacement? Are you going to try and patch it?

As others said the cylinder needs to be removed to evaluate. Some better photos of the piston and overall saw would also help us!



You asked for it, you got it! I'm on a pseudo-/work-vacation (drove back to TN from Humboldt....49 hours with ~4 hours of so-so sleep) working up my grandfather's 2000 sq.ft. veggie garden and building french-style raised beds, no wood barriers, and doing other odd chores for them. So I went to HFT and bought the tools I've lacked to tear this 550 apart.


In the photo with the red circle, that is a metal fiber, hair-thin, sticking out from the wall. Definitely some damage done, as you can see the reflection in the housing, though the cylinder is near spotless aside from one visible ding. The electric plugs had pitch INSIDE the plastic grooves; nearly unbelievable, but that's how dirty and packed with oily pitch this saw was before the initial cleaning (which now needs round two). The carb has pitch all the way down in it. None of this was knocked loose into the units. I can't find a model number on the carb, so presumably it is the original. The ring has dark spots which should be visible in the photo. The shaft itself looks good, no scoring, no bluing, no dents/dings. However, theere is the smallest bit of side-to-side play of the piston on the shaft, though it doesn't seem like the shaft is moving side-to-side. I will reinspect at another time.

In addition to y'all, I will be sending the photos to my regular saw shop/mechanic, and others who know saws/motors. Enjoy!

IMG_1594.JPG IMG_1595.JPG IMG_1596.JPG IMG_1597.JPG IMG_1599.JPG IMG_1600.JPG IMG_1602.JPG IMG_1603.JPG IMG_1605.JPG IMG_1607.JPG
 
HumBurner

HumBurner

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If the fuel tank was punctured, why is it optional for replacement? Are you going to try and patch it?

As others said the cylinder needs to be removed to evaluate. Some better photos of the piston and overall saw would also help us!


Yes, my intent is to attempt a repair of the tank first, then do a vacuum check. The original owner just slapped some weld over it, they didn't even try to work it into the hole or the groove created by the tossed chain.

The idea is to get this thing running for as cheaply as possible, if at all. I'm kind of on a budget, especially as I don't NEED the 550 in my lineup. I just bought a used, 2013 390xp, which ate up all my extra funds until it earns some money (bought it cause a client wants some bigger, just-starting-to-die trees down for firewood.)

Like I've said, this is mostly just for a learning experience, up to a certain price-point. I also have a Poulan 43cc I bought in December for $20 that I plan to tear down and put back together....should just need a new fuel line and a filter, but it was so cheap I might as well learn on it too.


Cheers!
 
HumBurner

HumBurner

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I'm presuming the bronzing on the depressed walls of the piston exterior is a sign of running lean. The shaft is also this bronzed color. Just noticed, one of the snap-rings has a slight hook exposed (to grab the ring), while the other ring is completely in the groove with no hook visible.


Seems odd, as if they should be identical unless something happened to one.
 
huskihl

huskihl

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I'm presuming the bronzing on the depressed walls of the piston exterior is a sign of running lean. The shaft is also this bronzed color. Just noticed, one of the snap-rings has a slight hook exposed (to grab the ring), while the other ring is completely in the groove with no hook visible.


Seems odd, as if they should be identical unless something happened to one.
The circlips on the newer saws are like that. Usually there's an access divot in the groove to get a pick into to remove the earless one
 
HumBurner

HumBurner

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So I finally found some free time, despite the complete and utter lack of rain this winter/spring, and started working on this saw again. Picked up an abandoned 550 (losing compression due to debris building up inside the cylinder/bearings; other possible issues as well as saw was incredibly dirty) for the tank handle and parts. Here's a write-up as of last use.
----------------------------------------------------------------------------------------------------------------

2013 550xp Pawn Shop Project Saw

(Initial details/photos on arboristsite, "How Bad is This Piston?")

Serial Plate info:
s/n 2013 0600488
966 64 82-00


-- Purchased March 2019 in poor physical condition (acquired parts-saw in March 2020 and salvaged some things for the project-saw.) Hand cleaned and later blown out with air. Cakes of debris everywhere except internally; muffler had 1/4"+ layer. Air filter was fairly clean. Spark-screen was clean. Case seams still have some gasket material showing.

-- Two Punctures in original tank-handle; patching attempts failed, but may try again in the future.
1) small hole underneath
2) Sizable tear & puntcures in elbow/interior groove

-- Cylinder and piston aren't terrible. Dirty, but not badly scored. Bearings free of debris. Piston-rod coloration is good, no excess play. Piston and cylinder were lightly cleaned with 2-stroke and fabric. Piston-ring in decent enough shape.

-- Right brake handle bolt-housing stripped.

-- Sprocket was very worn. Near-new chain came with the saw. Some Mg missing from saw and clutch-cover. Chain catcher in bad shape; filed down some.

-- Bar was badly beaten, not square, with chips in the metal, heat spots, burrs, etc.

-- Clutch was on backwards and would not come off with clutch tool or various hand tools AND an additional set of hands. Shop was able to remove. Replaced with 2-spring shoe style clutch. New needle bearing and 3/8 small 7-pin sprocket used.

-- Flywheel and starter-cover were very dirty. Recoil missing parts but functional. Swapped covers.

-- Muffler gasket was deteriorated. Base-gasket starting to wear, but reusable for short term.


Events
2/15/2020 - Sanded and removed original tank-handle patch attempt. My first attempt was unsuccessful. Acquired spare plastic from a 357xp top cover (cleaned and degreased) and attempted to fill/re-mold but did not make a seal. Small hole patch also failed. Plastic cools/cures too quickly to be malleable.


3/14/2020 - Acquired parts saw and swapped tanks. Put back together (less muffler gasket) and idled for ~12 minutes. Ran rough/hard at first but settled out; hard to turn over on first start, but subsquent attempts fire on 2-3 pulls. For short term, base-gasket is okay but will need to be replaced if saw is usable. Will also re-inspect and clean piston/cylinder. No loctite used on any bolts at this time. Gasket maker used where needed.


3/21/2020 - Saw hooked up to software at shop. No error codes present. Stats weren't alarming in regards to overheats or leans/leaks. Carb passed self-test. Forgot to get print out and hours, etc. Muffler gasket installed/sealed.


4/20/2020 - 2+ tanks ran through. Attempted to allow idle to set, warmed up, attempted to set auto-tune. Mixed results. Saw began to wake up some on the second tank.


4/21/2020 - 2 tanks ran through. First tank was pretty good. Second tank was pretty rough, with noticable issues idling and restarting. Purge bulb cracked.


4/22/2020 - Saw started on first pull, first-stage of choke; then turned over on first pull on half-choke. Let idle for 11+ minutes. Made a few cuts,nothing prolonged, gave a few blips. Proceeded to set autotune noodling all 18" of bar into a fir log. Let idle/cool for ~30 seconds. Cut cookies on the opposite end of log, 3-4 at a time, running wide-open for up to 45 seconds, switching cutting direction each slice. Let cool ~30 seconds. Made another noodle cut ~45-50 seconds. Let idle for a few minutes. Repeated process with cookie cuts until near end of tank. Let idle until running out of gas, ~3:15 seconds.
Let saw cool for a few minutes, refueled, and started back on first pull (no purge). Let idle for 13 minutes, blipped a few times, shut off. Restarted and shut off a few times. Pull-cord "responds" easier/smoother like maybe there was drag. Let sit for 6 minutes to cool and started again, first pull. Should run another ~2 tanks through it tomorrow. Only annoyance is a split-second lag when pulling throttle while revving; make note of this.

*Note: If saw shows potential after 10-15 GOOD tanks, will do compression check on cylinder. May want to tear saw back down, re-clean piston/cylinder and add new base gasket. Consider disassembling and cleaning carb. Decide whether to swap air-filter assembly (for purge bulb) or delete the bulb.


4/23/2020 - At the end of first tank of the day, chain tossed. Went to put everything back together and the outer bar-stud popped loose into the oil tank. The one tank of fuel went well with good throttle response, revving, etc. There were a couple of times where it didn't want to start easily, but for the most part it was a good tank. Tank 5. Do not know when bar-stud will be repaired.
 
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