iDRY Vacuum Kilns

Sponsors:

piston scoring

Started by tlbrooks, December 04, 2018, 07:17:57 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

tlbrooks

I bought a 880 that runs good and was told by the owner it had 20 hours of use  logging. I pulled the muffler and it had some piston scoring about one sixteenth wide in one spot from top of piston to just below bottom ring. cylinder walls look excellent. does  a small amount of scoring   justify a new piston before running the saw? ive got old xl homelite that runs  good with bad scoring. just wonder what other peoples experience is on the matter. thanks       

sawguy21

Can you post a picture of the damage? A shallow scratch shouldn't create any problems.
old age and treachery will always overcome youth and enthusiasm

Mad Professor

Is it running rich? Could be carbon scoring.

Pictures?

tlbrooks

im not sure how to post pictures . but a stihl mechanic said it was caused by water in the fuel. water mixed with fuel could cause carbon to free up I guess. it had some carbon build up outside the cylinder.

mike_belben

Look in the plug hole with a good flashlight and see if theres corresponding scores on the top of the bore above exhaust port.  In my opinion its usually the start of siezing from excess heat.  A grain of sand or chip leaves a single line.  If its kinda started to smear a margin to me thats too lean/too hot.  Nothing is perfectly round when you get into the ten thousandths so starting to lock up along a 'high spot' would be pretty normal.  

If the bore is perfect id change the piston.  If its scored too id probably fatten up the mixture and run it.  Just remember to let the fan do its job by idling periodically. A muffler mod cools things down too in my experience.  
Praise The Lord

tlbrooks

ill check the plug hole. I checked it with the tach at 11 200 and that's was as rich as it would go so I pulled the limiter and trimmed the tab and set it at 10000. now it blubbers a little. all I was going to do was mill with it but I need a bigger bar it has a 25 on it.

Mad Professor

This PDF might be helpful

tlbrooks

that's some good information. its not been a good day my oe stihl piston stop end broke off inside the cylinder while I was removing the clutch. 

Thank You Sponsors!