550xp service

[mbrick]

Hi guys, I picked up a used 550xp for myself. Photos below.

I am wondering if I should put a new ring on the piston. Doesn't 'feel' like it has a ton of compression.
I do not need to use the decompression button at all for starting, where on my 455 it makes a large difference. It will hang on the starter cord and not drop. Ordered a 10mm adapter for my comp gauge, results soon.
It's inexpensive and easy, only $11 for a ring and base gasket.
Piston is probably OK (will measure) because I still see machining marks.
Hard to get a photo of the cylinder bore, I see cross hatching and not too many vertical lines.

Do I need a new bar? Guessing this is the original bar it came with. Sprocket spins easy. Chain is shot, I'll get a new LPX.
Do I need a new rim? I think these are wear indicators?
Do the decompression buttons leak on these (Are people installing the plug?)
Any reason to move to the newer 2 shoe clutch? $30. Some discoloration but not bad.

Don't know total hours used so I included a photo of the side covers. Only dealer nearby charges $65 to read the hours from the autotune....

Cleaned the mesh filter, removed and cleaned through the oil line on both sides, greased clutch needle bearing, getting a new spark plug and primer bulb. Will pull the carb and make sure it looks ok and doesn't have any crap built up.

Anything else I should check out or replace?

 

[Dave27483]

I have now done up 3 550xps and usually I will de carbon the jug and renew the piston and ring. I also de burr all the casting defects out of the jug.
This gives the little saw a real noticeable pick up in power and compression.
Just a hint if you do try and remove the jug leave all the carb attached. You can then remove the carb and intake on the bench. Then reverse when installing, this makes the job so much easier.
Good luck I really enjoyed working on and using this saw. Have fun

 

[Dave27483]

Don't forget to muffler mod! Plenty of post about that on here

 

[mbrick]

I have now done up 3 550xps and usually I will de carbon the jug and renew the piston and ring. I also de burr all the casting defects out of the jug.

What kind of tool do you use to de-carbon the jug? Is the bore plated with nikasil or chrome?

Do the transfer covers have a gasket or o-rings? I'll need a security torx bit.

What kind of bit do you use for deburring and removing flash?

Thanks for the input. I think I will tear it down after all then and at least replace the ring. It's about $50 for the piston kit with ring, wrist pin, bearing, etc.

 

[weedkilla]

If you use an adapter on your compression tester you will see very low numbers. The extra volume in the adapter screws with the reading.

The bar and sprocket look fine, but a new sprocket with a new chain won't break the bank. Dress the bar.

Id just run it before I made any decisions on the clutch.

Decomp valves can leak. You'll see a plug that has a white section like a pizza with a slice missing.

On mine I found I could cut a thinner gasket and set the squish to .020", with a muffler mod that makes for a nice saw.

 

[KenJax Tree]

Andrew did you redo the muffler or leave it as i had it?

 

[weedkilla]

Left it as you did it. Couldn't see any need to do any more.
The casting flash in the transfers was pretty bad. I'm sure cleaning them made a big difference in that saw.

 

[mbrick]

If you use an adapter on your compression tester you will see very low numbers. The extra volume in the adapter screws with the reading.

The bar and sprocket look fine, but a new sprocket with a new chain won't break the bank. Dress the bar.

Id just run it before I made any decisions on the clutch.

Decomp valves can leak. You'll see a plug that has a white section like a pizza with a slice missing.

On mine I found I could cut a thinner gasket and set the squish to .020", with a muffler mod that makes for a nice saw.

Good point, the adapter would be ahead of the schrader valve. How do you decide when to re-ring a saw, if not based on compression?

I'll get a new rim, inexpensive and I agree. Ok, will remove the decomp valve and snap a pic.

 

[weedkilla]

Ok, will remove the decomp valve and snap a pic.

Sorry. Bad explanation.

The spark plug will have the white pie shape on it.

 

[mbrick]

Sorry. Bad explanation.

The spark plug will have the white pie shape on it.

Oh, right. That makes more sense, white near the air leak/more lean area. Plug was evenly black so I'm good then.
I misread plug as decomp plug, it's not a plug. Doh.

 

[Dave27483]

Ok to de carbon I use scotchbrite , sand paper, and a mini bench grinder with a pencil attachment that I brought from the local mall for $40! Plus all the bits to go with it for another $40. I wire wheel or sand paper barrel works well for cleaning out the exhaust port. To put some fresh cross hatching on the walls I used the randy Evans (mastermind) method shown here on AS.
The transfer caps have o rings and I reused them no problem.
Yes you will need security torx bits to remove caps.
And for debburing I use a small stone piece on my pencil grinder and wet and dry to finish off.

 

[Dave27483]

Here is some tooling

 

[weedkilla]

Here is some tooling

That's pretty cool Dave.

 

[Dave27483]

That's pretty cool Dave.

Thanks mate, I don't expect to be the next Snelling or randy but I do enjoy just tinkering and making an engine perform as it should or a bit better

 

[Big_Wood]

if it runs good i'd forget the ring and run it til it absolutely needs it. very interested in the 3 shoe clutch. must be from a 562? i'd like a 3 shoe for running 3/8's as the dual shoe springs get weak pretty quick. unless i'm thinking of another saw and my 550 has a 3 shoe. i'll have to look as i can't remember.

 

[mbrick]

if it runs good i'd forget the ring and run it til it absolutely needs it. very interested in the 3 shoe clutch. must be from a 562? i'd like a 3 shoe for running 3/8's as the dual shoes get weak pretty quick. unless i'm thinking of another saw and my 550 has a 3 shoe. i'll have to look as i can't remember.

Yes, that's one take, just run it... but for such minimal cost I wouldn't mind making it run tip-top.

The 3 shoe was an early part on the 550xp and then got updated from what I understand. The 2011 IPL shows 3 shoe, 2013 IPL shows 2 shoe. I did find one other poster on here who commented asking if he should upgrade the 550 to a newer 2 shoe but there was no conclusion.

I agree with you, it seems like the 3 shoe will engage more evenly, and be stronger and wear better. Maybe there was a weakness in the spring design, etc.

The hub/drum changed part numbers from 575 26 10-01 to 575 26 10-03. I do not know if the dimensions changed or there was some other small improvement made. Same rim.

Edit: the 562 still uses the same 3 shoe so you could order it for your 550... unclear if your drum will work with the 3 shoe. I could measure mine and you could compare, since i have a 3 shoe and you have a 2 shoe drum?
562 3 shoe: 574 23 61-01
drum in .325: 575 26 10-01
drum in 3/8: 575 26 10-02 (only diff is the rim)

 

[Big_Wood]

dang it, mines a 2013. i really don't wanna go to the shop the check but i think i remember it being a 2 shoe. i think 2 shoe is just fine but the 3 shoe would be better for running 3/8's chain.

 

[weedkilla]

Same diameter on the 562 and 550 clutch.
3 shoe on the 562 and 2 shoe on the 550.

 

[Dave27483]

I don't remember where I read this but I believe they went to a 2 shoe design for reduced rotating weight which increased throttle response

 

[Ferguson system]

Looks like the saw could use a new rim. I'd also consider a new bar. You could try dressing it, but the damage near the sprocket doesn't look too good.