346xp Scored Piston

[sunfish]

Yep, cylinder looks good, just remove the aluminum.

As far as what else to do, make sure you find out what caused the problem to start with.

 

[Mtnyota]

Ya I tried to pressure/vacuum test but the sparkplug air adapter I had was leaking pretty bad around the threads, even with teflon (I need a jam nut and a oring). I pressure testing with soapy water and was unable to see any leaks around the cylinder gasket, crankseal, or intake boot. I will retest once I get it back together. I'm guessing it was just ran lean do to me hearing the rev limiter and thinking it was fourstroking. B/c of that I though it was tune right and never adjusted it.

 

[sunfish]

That saw is likely too new to have a major air leak, so you're probably right. My old one has never had one, except where the carb bolts to the intake boot flange, an easy fix. You should be good to go after getting it together and re-tune.

 

[Stihlofadeal64]

I think I lucked out. The cylinder in my newbie opinion looks like it should be fine. Ive still have some transfered alum to removed, but I think it should be good. I plan on getting the meteor piston kit and putting it back together. Is there anything else I should order/replace while I'm in there? I ordered a tach and I'm thinking about an unlimited coil.

Out of curiosity, what were you using to slick up the cylinder. I personally wouldn't reassemble it till I was able to slick it up a bit more. I may have to duck after this comment but a "ball hone" would make it look real slick. :msp_w00t:
If it doesn't have an apparent leak from the final test, it may have indeed been the carb tune.
Happy Sawing.

 

[Mtnyota]

I have been heating up the cylinder and using muriatic acid to dissolve the transfered aluminum. I lightly wet sand with some 500 grit sandpaper. I'm not sure on the hone issue i've read both it is good and it is bad. If possible i'd prefer not to have to buy the hone.

 

[jus2fat]

Forget the hone..you don't need it.

Just continue on as you're doing..it just takes time..:msp_wink:

J2F

 

[sunfish]

Yep, no hone, just get all the aluminum off the bore. And go easy with the sand paper, 500 maybe too fine? Ya don't want a mirror finish in there.

 

[jus2fat]

I use 400 grit 'wet or dry' sandpaper..and use it WET (soaked in water)

500 grit is for polishing...use that grit at the end..!!

J2F

 

[Mtnyota]

What I have been doing is use the acid until it appears to not be working. Then I rinse and sand it wet a few swipes with the 500. Then I heat and reapply acid and repeat the process. So you're saying to use 400 wet'n'dry sandpaper, and then at the end finish with 500 grit? Or just leave the 400 grit finish?

 

[jus2fat]

You can use the 500 grit at the end if you choose..

It's not really necessary if you use the 400 wet..!!

J2F

 

[Mtnyota]

Well I'm back with my tail between my legs. I got the saw back together, and took it to have a shop tune it. I let it warm up yesterday check the tune with the tach(It was 13,900 rpm). I then started working up the tree. Well after about 5 cuts as soon as I finsih the cut the saw died. This is what happened last time. SO I stopped and pulled the muffler and sure enough the piston is starting to show some scoring on the side of the piston.

So my question is, is it possible to be running lean at 13,900rpm?

 

[lone wolf]

I think I lucked out. The cylinder in my newbie opinion looks like it should be fine. Ive still have some transfered alum to removed, but I think it should be good. I plan on getting the meteor piston kit and putting it back together. Is there anything else I should order/replace while I'm in there? I ordered a tach and I'm thinking about an unlimited coil.

 

[lone wolf]

Well I'm back with my tail between my legs. I got the saw back together, and took it to have a shop tune it. I let it warm up yesterday check the tune with the tach(It was 13,900 rpm). I then started working up the tree. Well after about 5 cuts as soon as I finsih the cut the saw died. This is what happened last time. SO I stopped and pulled the muffler and sure enough the piston is starting to show some scoring on the side of the piston.

So my question is, is it possible to be running lean at 13,900rpm?

Yup you didn't pres/vac test it properly did you? What did you put in to the repair any new parts ring,pist? did you just slap it together after cleaning the cyl w/o new parts?

 

[Mtnyota]

I did vac/pressure test it. I put a rubber gasket between the carb and intake boot as well as the muffler/cylinder. I applied vac/pressure through spark plug hole.

I replace the piston/ring/gaskets/intake boot/fuel line/fuel filter/breather last time I pulled it apart. I'm gonna redo the vac/press test before I tear it down.

 

[lone wolf]

What oil and gas are you running? What is the heat range of the plug in there is it the correct one? I would run it at lower max rpm till the piston breaks in. Your gas may be bad. There could be a vac leak in the manifold that was not tested. Did you do vac test also?


2 stroke failure

Possible causes:
too low an octane fuel used or fuel with too much alcohol used.
jetting too lean or failure of the fuel system, i.e., clogged fuel line or filter, fuel tank not venting, problem with fuel pump, carburetor, air leak into crankcase
spark plug heat range too hot
ignition timing too far advanced, possible failure of the c.d. amplifier box
restricted exhaust system: back pressure too high
overheated, loosely-installed spark plug

 

[sunfish]

Yes, it could be too lean at 13900. Was it 4 stroking?

Either air leak, carb adj too lean, didn't get all the aluminum transfer off, or the old jug is no good.

What was comp after it was all back together?

 

[lone wolf]

Yes, it could be too lean at 13900. Was it 4 stroking?

Either air leak, carb adj too lean, didn't get all the aluminum transfer off, or the old jug is no good.

What was comp after it was all back together?

Could be the old damage tearing the new piston up right?

 

[Mtnyota]

91octane / with husky synthetic oil.
I'll need to check on the plug it was tight though.

 

[sunfish]

Could be the old damage tearing the new piston up right?

Yes, could be.

 

[lone wolf]

91octane / with husky synthetic oil.
I'll need to check on the plug it was tight though.

Check the numbers make sure correct plug.Was the cylinder very clean or did the old damage scape the new piston? Was an actual Vac test done along with the pressure test? Could the manifold be leaking air?