357XP Replace cylinder or just piston? (Pics)

[edrrt]

This is the second time this has happened to me on this saw. The first time my dad put straight gas in it. It looks similar and I used acid and sandpaper to clean the inside of the cylinder and just added a new piston. It wasn't perfect but it looked pretty good. I am wondering if this contributed to the new piston failing? Or could it be something else?

I'm using 2.6 mL of 2 stroke engine oil for 1 gallon of gas.

Anyone have thoughts on what caused this and if I should just try and polish down the cylinder again or if I should just replace the whole top end this time?

 

[RED-85-Z51]

What oil do you use...ethanol content of fuel?

Sent from my LM-G820 using Tapatalk

 

[Bob Hedgecutter]

Might be a fuel mix problem?
2.6ml is NOT 2.6 fluid ounces is it?

 

[edrrt]

Might be a fuel mix problem?
2.6ml is NOT 2.6 fluid ounces is it?

Sorry I meant OZ.

Its the standard ratio off the shelf.

Also any reason not to grab one of the 30 dollar rebuild kits off Amazon?

 

[Yukon Stihl]

Not worth the money
Did it pass Vac and Pressure tests?

 

[Bob Hedgecutter]

Sorry I meant OZ.

Its the standard ratio off the shelf.

Also any reason not to grab one of the 30 dollar rebuild kits off Amazon?

Well, unless you discover why it burned up twice- either fuel ratio or air leak, then sure- run with the cheapest top end kit you can find, because you will be replacing it again in the very near future if the problem that caused this is not corrected.

 

[holeycow]

And you'll be taking out the bottom end too..if you haven't already.

 

[Huskybill]

I think it’s time to tear it down and do the crank bearings and seals, as well as the top end too. Then pressure test it.

When I was new to two strokes I burned up two pistons then I was taught about pressure testing in dirtbikes. Doing it right saved me money and time in doing it over. Note: the crankbearings can feel ok when the case is assembled but when taken apart the feel lots of play in them. When the pistons cost $200 for my vintage husky bikes I make no mistakes even with my saws.

 

[cuinrearview]

Looks like you caught it early. You may have not cleaned it up all the way the first time. Post pics after this round.

 

[edrrt]

Looks like you caught it early. You may have not cleaned it up all the way the first time. Post pics after this round.

I think probably what caused it to fail was me not getting it perfect the last time. How good does it have to look? And does that cylinder look salvageable? Am I just wasting my time trying to rehab it?

 

[Mad Professor]

I think probably what caused it to fail was me not getting it perfect the last time. How good does it have to look? And does that cylinder look salvageable? Am I just wasting my time trying to rehab it?

You have to get all that aluminum smear off the cyl plating. Then see if plating is damaged beneath it.

Here are pictures of a 036 piston and how the cylinder cleaned up

 

[hotshot]

Sorry I meant OZ.

Its the standard ratio off the shelf.

Also any reason not to grab one of the 30 dollar rebuild kits off Amazon?

+1, No Chinee kits, go back with OEM.

And 2.6 in 128 oz is 50:1, but I’d start running 32(4 oz) or at least 40:1 (3.2 oz) after the rebuild, given the track record of your saw.

 

[cuinrearview]

I think probably what caused it to fail was me not getting it perfect the last time. How good does it have to look? And does that cylinder look salvageable? Am I just wasting my time trying to rehab it?

I think it will clean up fine but be careful at the port edges. Every spe I of the aluminum needs to be removed. This is how I do it:
https://www.arboristsite.com/community/threads/transfer-removal.340325/

 

[edrrt]

New top end arrived. 30 bucks from China. It looks really different. Transfer ports look very different, all holes are smaller.


I cleaned up the original but lost some plating by the exhaust port.

Which cylinder should I try?

 

[rob066]

what year of manufacture. The early 357 were prone to air leaks from the auto decomp as well as the plastic intake clamp.

 

[cuinrearview]

New top end arrived. 30 bucks from China. It looks really different. Transfer ports look very different, all holes are smaller.
View attachment 823386

I cleaned up the original but lost some plating by the exhaust port.

Which cylinder should I try?
View attachment 823389

I would not use either. The OEM one will work for a while but that's a lot of missing plating. The China one won't run nearly as well and from the looks of the port edges will beat rings up bad if it doesn't catch one. HL supply recently sold complete OEM 46mm top ends for $120. Even if you pay a little more it's worth it. I think you're seeing why.

 

[edrrt]

what year of manufacture. The early 357 were prone to air leaks from the auto decomp as well as the plastic intake clamp.

Purchased in 2007. And it may have burned up just because the mix was wrong.

 

[rupedoggy]

I have noticed some people don't have a "feel" for this stuff.

 

[cuinrearview]

I have noticed some people don't have a "feel" for this stuff.

Trying to give solid advice here is like sticking fingers in a dike.

 

[cuinrearview]

Which cylinder would @noodlewalker use?