550XP Couple of Questions

[notmyj]

Hey guys, I picked up a 2014 550XP with a scorched piston. Got the factory P&C kit, replaced the crank seals, new base gasket etc. Got it back together, but the new kit came with a plug for the Decomp. Is this a change that is recommended or just an option to delete it? It looks like the old one had a transfer leak, as it looks overheated on one side of the cylinder. It does have a newer AT12 carb on it, so I'm guessing it was replaced. Once the new rim sprocket comes in (going to run 18" 3/8 .050 to keep things simpler here at the house, and let the 357XP wear the 20") I'm gonna take it to the dealer to get carb reflashed/cleared.

Should I keep delete the Decomp, or put it back in? Any other updates that are "must do"? It looks to have the old style top cover too.

 

[BenK]

I have a 555 and it has a decomp on it. Ive never used it. Call me paranoid, but I am worried it will stick and then cause problems (I have inquired about deleting it and will some day). I can get the saw going without it, and honestly for most I don't think it is necessary. All things being equal removing a part that has no benefit to me, but could fail and cause problems seems like a good proactive move.
I would imagine with the 550 being a bit smaller, the need for a decomp would be more "the exception" than the rule....so to speak.

 

[Jed1124]

Delete the decomp.
Did you check the transfer seals? They are known to leak.

 

[Icedogs28]

I'd delete it. No need for decomp on a 50cc saw. One less thing to leak

 

[old guy]

Take a look at the new top covers, it's easy to take a dremmel & grind your cover the same way, that's what I did. I like decomps, they save wear & tear on the starter & my nearly 80 year old arm.
All new cyls. come with a decomp plug. The transfer seals are what ruined the one I got but the new ones should be o k.

 

[notmyj]

Thanks guys. I think there was an update to the cylinder as it showed a newer part number, my understanding is they fixed the bad transfer seals on the new ones hence the new part number. As it's a new factory part should I do anything to the new one or run it as is? I didn't mess with them at all on the new one.

 

[spike60]

New top end part number is 577764705, due to a new wider exhaust port and a different piston profile. Transfer seals were corrected some time before that.

And yes, Id get rid of the deco also. Decos leak more often than you'd think.

 

[notmyj]

New top end part number is 577764705, due to a new wider exhaust port and a different piston profile. Transfer seals were corrected some time before that.

And yes, Id get rid of the deco also. Decos leak more often than you'd think.

Now you got me thinking I should delete it on my 357 also... But without a primer bulb, the decomp is nice on that saw.

 

[furb]

Does anyone know what serial # the seals were corrected at?

 

[notmyj]

Ok, the rim sprocket (3/8 x 7pin) showed up today. Got it on, put a bar and chain on it and it fired on the first pull. I did a MM while I had it off, wow this thing is loud, it has an authoritative "pop" to it. Didn't have any wood to cut, other than slice a few pieces of of split fire wood, but it seemed to run ok, the idle wasn't very smooth, and I'm positive I'm using different fuel/oil than the previous owner. I run AvGas and Amsoil Sabre at 80:1, although I added a small bit more of oil to this tank and the bearings and seals were oiled prior to assembly with Sabre so I'm sure its heavy on oil right now.

My next question, is should I take it to the dealer to check the firmware for updates/reset or just let it figure its self out? I'm pretty stoked as this was my first full rebuild on a parts saw from ebay. I got the saw for $133.

 

[Evan]

What does a primer ball have to do with a decomp.

Ive ran lots of 70cc and a few 90cc saws all pushing in ballpark of 180lbs compression. Only one i ever used the decomp on was the 066 at the end of the day when id get worn out. I got to were i figured if i was to to tired to pull the rope with enough energy then maybe i was to worn out to safely run a saw.
I could see a tree guy hanging upside down in a aquard position finding the decomp usefull. Most pro type saws have them for that reason they are sometimes benifical but not always needed.

I like that my ms440 doesnt have one. Itl be ported and i hope pushing 180+ compression

 

[notmyj]

What does a primer ball have to do with a decomp.

Ive ran lots of 70cc and a few 90cc saws all pushing in ballpark of 180lbs compression. Only one i ever used the decomp on was the 066 at the end of the day when id get worn out. I got to were i figured if i was to to tired to pull the rope with enough energy then maybe i was to worn out to safely run a saw.
I could see a tree guy hanging upside down in a aquard position finding the decomp usefull. Most pro type saws have them for that reason they are sometimes benifical but not always needed.

I like that my ms440 doesnt have one. Itl be ported and i hope pushing 180+ compression

Since the the 357 doesn't have a primer, and it sits for months on end, it's nice to have the deco as it takes 6 pulls or so to get it started, as it has to suck the fuel back up from the tank since there is no primer.... And since it too has 185psi compression, the deco is nice to have after it has been asleep for a while.... But then again perhaps I'm just not as much a man as you? Lol