Ported 2511, scored P&C

[AudunM]

Hello all.

This is my first post on this forum and i want to thank you for all the chainsaw wisdom shared.

I recently bought and ported a brand new Echo CS2511T. These are the steps i followed:
-I opened up intake and exhaust. Exhaust roof was raised and intake floor left stock.
- The lower transfers were opened up and the insert pin was removed.
-To match the lower transfers to the transfer case, the latter was disassembled. I did not think i would be able to grind the transfer case without aluminium dust getting in the crank bearings.
-When i assembled the transfer case one of the crankshaft seals must have become slightly damaged. On "post mortem" inspection this is clearly visible.
-The flywheel key was so tight that i did not get it back together without removing some material from it. This resultet in about a 2 degree timing advance.
-The saw was reassembled without base gasket with Permatex Supra Blue.
-The muffler was left stock other than prying it more open with a screwdriver.

Test running the saw:
-When first firing up the saw it sounded great and idled smoothly.
-I let it idle for about 10 minutes and then started cutting 2-4" birch.
- With screwdriver in hand i got to work on the wood pile without pushing the saw hard or going full beans. I had prepared a goofy filed loop of stihl picco super and the chips were flying. I was really happy with the performance of the saw at this point.
- After about 10 minutes of work the saw starte acting up. It would not run unless i startet to tune it richer and richer. I probably should have stopped sooner but in the end it would not run unless the L-screw was set to about 3,5.
- At that point i was suspecting an air leak.

Upon disassembly i found that the piston had scoring marks between the top of the piston and the piston ring, but exhaust side only. There are scoring marks on the cylinder wall aswell, but in contrast to the piston ones, I am not able to feel these when touching the cylinder wall.

I am relative green in this field but my current idea is the following:
Air leak in the crank case due to damaged crankcase seal has lead to lean running conditions and scoring?
Possibly i have done a poor job at bevelling the exhaust port roof which can cause scoring as well?
The scoring on the piston are not exclusively in the area of the exhaust port though.

If you think my reasoning is off or have other ideas as to the reason of failure, i would appreciate feedback. Hopefully my next motor will last longer than one tank

Best regards
Audun, Norway

 

[AudunM]

More pictures of the port work.

 

[AudunM]

That concludes the picture uploads.

 

[huskihl]

You need to bevel the exhaust port a bit. Fortunately nothing got hurt too bad. You can see in your picture where you snagged the roof of the exhaust and it stuck the ring. Should be able to remove the ring carefully and make sure it’s not damaged, clean up the transfer marks on the cylinder and your ports. Hard to tell if the seal is bad or not but you may have lost the spring on the inside. Make sure you oil the seal lips when you slide the 2 halves together

 

[AudunM]

Thank you huskihl. I did as you said and reseated one of the crank seals that seemed to be off center. The saw ran great for lonh enough to make the linked video. Shortly after i stoppet filming the same symptoms began. I will disassemble and have closer look at the seals. Thanks for quick reply and help.