Hey all, I know how to read a plug, but what is a piston wash? Thanks

Piston wash is the actual washing of the piston crown in the area of the transfer ports.

Too much fuel and you will have a LOT of wash(rich), too little fuel and there is no wash( lean).

The wash will look like clean spots about the size of a finger nail right at the edge of the piston where the transfer ports are.

Remember: ***Carbon only sticks to a HOT piston***

We do jetting so that the dome is covered in that light grey/brown color...covered in carbon.
For correct piston wash the piston must be nearly completely covered in carbon.
The 4 little fingernail size 'White' areas are where the carbon is Washed off due to piston cooling being the greatest in that area.

If there were no fingernail size areas and the top of the piston was total covered in carbon, the engine would burn down from being too lean.
The bigger the fingenail 'white' areas get, the more RICH the mixture is.
The fuel is greater and is keeping the piston cooler so there is more carbon 'washed' away.

the 3 pistons on the bottom there, the left piston is Rich, the middle is Not so rich, the right piston is acceptable for x-country use or trail, what have you.

I run my sleds like the piston in the center-right of the page. You can see the white areas where the carbon is washed away from the intake transfer ports, the exhaust side is completely covered in carbon.

Joe,

Your getting that kinda wash from a Doo seriesIII?? I am finding it to be VERY difficult to read wash on THESE engines. Could be the type of oil??? I am using Klotz...

I have NO wash and my plugs and EGT's are telling me I am too rich.. what to do?? Lean or rich the crown looks the same...

Hey Pete, yeah my 440 pistons have beauty wash. I kept not about how much fuel it took. It took me around 7 gallons of fuel to build wash. I am just using premix phillips injex.

The 800 my pal has took a long time to come around though, but we can see wash on it now. I think it took him around 10 gallons of fuel and running around to get wash going.

laterz
Joeyz

On the 800 with the Klotz oil, just ride it for a much longer period. Klotz is one of the best oils available for sleds. It burns very clean. Just ride it and enjoy. Good choice on oil! :)

So do you need to take the head off to look at the piston wash?

No,

You can do it with a inspection light or bendable light some call it. Take out the plug and you can put this type of light down in there and see what's going on.

There is also a tool called a borescope that works even better, but is really expensive.