Engine carbon buildup vs operating temperature

[W.duBois]

A tech question, I have re-assembled my chainsaw today and something popped up in my head when I saw mild carbon buildup on the piston head (crankcase and piston/engine walls where factory clean).
I know that carbon buildup occurs when the temperature inside the combustion chamber is to low to burn away the carbon particles.

Knowing that I wonder.. I, and after seeing many other carvers, don't use full throttle that much. I can control the saw better when the RPM are a bit lower and with a sharp chain the results are just as good. However, these engines are designed to run at high temperatures, not half throttle all the time..

Do you guys 'gun' your saws or use lower RPM's like me? What does the top of your piston looks like? And I reckon that mixing your own fuel will have more pollutants in it then pre-mixed fuel such as the Aspen fuel I use.

(offtopic, please send my little saw some prairs that I haven't messed anything up inside the engine... It sounded good and acceleration was normal. But still...something could have gone wrong, piston rings, gaskets, pollutants etc. Ykes..

[highsierrabear]

Yeah, we don't use these tools the way they were designed. I was always taught that chainsaws have 2 speeds, idle and full throttle. That goes out the window, along with most other guidelines for using saws.

I think 2-stroke engines are meant to run high RPMs to get proper airflow, backpressure, and power through the engine.


What can you do, besides keep them clean, do some periodic maintenance, and buy quality saws.

[VesselMaker]

Originally Posted by highsierrabear

Yeah, we don't use these tools the way they were designed. I was always taught that chainsaws have 2 speeds, idle and full throttle. That goes out the window, along with most other guidelines for using saws.

I think 2-stroke engines are meant to run high RPMs to get proper airflow, backpressure, and power through the engine.


What can you do, besides keep them clean, do some periodic maintenance, and buy quality saws.

What you can do is run a good quality fully synthetic 2 stroke oil like Stihl Ultra, or Mobil 2T (discontinued) or a number of other high performance oils.

And a big benefit of full synthetic 2 stroke oil is that there is much less smell and smoke. I would never go back to dino oil in my saws.

Some would argue that a ratio more concentrated than 50 to 1 is better, but I am not going there. Plenty of threads about it on arboristsite.com.

[Rwenzoski]

Hi Walter, Sandor & Wesselmaker. As said, the first most important aspect is the mix used & the ratio being dead on correct every time, no matter what the situation. The second is to keep the gas fresh, high octane & clean from debris, sawdust etc. keep the caps on at all times & when using clean the sawdust & crap off the tank & the gas can, same with the bar/chain oil. The direct identifier for how the saw is running or any other engine for that matter is the spark plug colour. It should be light brownish right to a greyish colour or if it is black way too rich of mixture or totally white, too lean! Yes, I agree saws should be used across the entire RPM range the same as any other engine but can be used at lower RPM's for long periods also as long as you wind them up once in a while. Just keep in mind that adjusting any carberation should only ever be done once all other factors effecting the mix is known to be correct first! Most carbon build up results from ne of two things, first is normally too rich of mixture which will in tunr cause the saw to run cooler so this is the first thing to make sure is correct the second is from not running the saw up in RPM enough to create the heat to begin with.
Thanks, Robbin