piston "wash"

[anziconda]

Could someone please explain this to me and possibly post some pictures of desirable "wash" as well as bad "wash"...thanks, I'm a noob with 2 stroke engines.

 

[LRD]

Here is a link to real SnowTech article on this subject with pictures.

http://www.snowtechmagazine.com/articles/2001/baseline/baseline.php

Been a while since I really read this through but I don't think it covers this.
Single ring pistons (doo) read different from two ring pistons. Single ring piston domes run hotter and will show less wash when jetted the same as two ring pistons which run cooler as they have double the heat flow path out of the domes to the cylinder walls and cooling system. Example single ring might show wash 1/4 of dime size while two ring might be dime to nickel size. I am doing a lot of work to switch my engine over to two ring pistons in my mod Long track TNT for cooler piston domes and more reliability.

Good Luck

 

[anziconda]

Thanks for the link...It didn't totally explain it though. Is it just the way the black(carbon) coats the piston or is there more to it. Snowtech is by far the best magazine ive ever found for snowmobile info
Any additional input would be greatly appreciated.

 

[devilrmk]

The piston gets hot from combustion. The area just by the transfer ports has cool air/fuel mixture flowing by it all the time therefor making it the coolest place on the piston. The heat of the piston turns the oil into carbon stuck on the piston. Jetted correctly there will be a very small area at the transfer port that gets "washed". It is not hot enough there for the carbon to stick. If you are too lean, the wash goes away, if you are too rich it washes more of the piston. Pretty simple once you know what is really going on.

 

[catman01]

Look in the performance/modified section there is a thread on piston damage that has some good info about piston wash and reading plugs!

 

[drmiller100]

the pics in the snotech article are pretty good.

acceptable to me is too lean. i like to see a little more wash then that. the rich is too rich though.

look at your finger nail on your middle finger. that is the size you want to see.

 

[LRD]

Click on the little box to get about the best spark plug reading diagram out there. Mixture, plug heat range and ignition timing all in a nice little diagram, print it in color and seal it in plastic and keep it in the tool bag.

http://tsrsoftware.com/sparkplug.htm

Good Luck

Reading domes is the best unless you have a doo or XP or don't have a bore scope. Then its learn to read plugs.

 

[anziconda]

Thanks for all the input guys...All info was very helpfull. I guess S.W. isn't just a bash fest afterall...there is a wealth of knowledge on here when put to good use. Best of luck to everyone...ride hard and be safe!!

 

[NoSecondChances]

Click on the little box to get about the best spark plug reading diagram out there. Mixture, plug heat range and ignition timing all in a nice little diagram, print it in color and seal it in plastic and keep it in the tool bag.

http://tsrsoftware.com/sparkplug.htm

Good Luck

Reading domes is the best unless you have a doo or XP or don't have a bore scope. Then its learn to read plugs.

The TRS plug info is awesome! I recommend that literature for sure. Reading pistons is a lot more than just looking at the wash pattern to determine jetting, and please remember that it takes a long time for wash to develop, where plugs will change in a matter of seconds. Make moderate jetting changes, get a good EGT or A/F gauge and talk to F-Bomb on here and read the info on his site about setting a baseline for your sled, he is a wealth of knowledge on the subject. Search the forums for plug reading threads, you will find lots of info here.