Piston wash patterns

[huskyboy]

The glare kinda messes with reading this picture. After a tank or so I pulled this saw apart to look at wash (was the first and only saw I did transfer work to). I was satisfied with what I saw, looked even enough.
View attachment 141198

The mean black 350 husky you had in pa?

 

[Wolverine]

The mean black 350 husky you had in pa?

Yerp. It's a Jonseblack though.

 

[MustangMike]

The method of compression is different. The key is screw chargers are more efficient, capable of higher boost and have a less pressure fluctuation and the price coincided with the benefits.



Not really. Roots, (sealed or unsealed) have matching profile vanes that are either straight or have a pitch of less than 1 turn for the length of the rotor multipled by the number of vanes so the vane can seal against the house of the blower.

A screw charger usually has vanes with different profiles per screw. The pitch of the vanes are greater than 1 turn per the length of the screw.

Thanks for that explanation. I knew there were differences in performance and efficiency, but was not exactly sure why. The twin screw seemed like it best suited my needs, plus 50 State emissions legal is a plus.

 

[Sawsparky]

The PTO side of the cylinder is always going to be running hotter than the flywheel side and thus have more carbon build up. The angles of the piston wash should show up pretty similar per side but the size and distance of the wash is going to be different due the the temperature gradient. Unless the saw only makes 3 cuts and gets to cool down.

Just thought this was interesting? Flywheel side has much more buildup. Possibly trans timing difference? 394.

 

[tree monkey]

poor tune, poor oil, and yes the ports don't match

 

[bwalker]

poor tune, poor oil, and yes the ports don't match

This.

 

[JohnnyBlade]

 

[Stump Shot]

View attachment 175316

Looks like one leg is in a gold mine and the other in the *s-wordhouse.

 

[Terry Syd]

Put the piston in the bore and shine a bright light up through the transfer ports while looking through the sparkplug hole. I expect you will see the flywheel side ports open much earlier than the PTO side.

 

[JohnnyBlade]

Could be a lil off on my grinding. Opened her up to get back in. If anything the saw will be lighter. The driver side looks awsome. Pass side doesnt look like its seeing any charge. I did open the transfers twards the intake just slightly earlier than the exhaust side.....???

 

[huskihl]

Could be a lil off on my grinding. Opened her up to get back in. If anything the saw will be lighter. The driver side looks awsome. Pass side doesnt look like its seeing any charge. I did open the transfers twards the intake just slightly earlier than the exhaust side.....???

Looks like the left opens 3 or 4° earlier. Or the right side is more restricted down in the lowers

 

[usmcbuckwild]

I try to clock all my plugs; it was ingrained in me from a young age. The cylinder design dictates where the ground strap SHOULD be located for maximum efficiency of the spark to trigger the flame kernel and not interfere with its expansion.

There is probably a reason why some cylinders are designed with an angle to the spark plug hole and the actual spark plug tip being placed in a very specific location at a specific depth. I’m not saying specifically 2 stroke engines, but why wouldn’t that same thought process work in these engines.

In regards to reading the piston; its already been proven in this (and other) thread that there is a gross amount of information that can be accumulated from the wash pattern left on the piston. We all know that you can tell quite a bit from a piece of metal by the colors it displays. I believe the same can be said for the piston. If we have carbon build up from heat on the piston, we can narrow down hotter locations inside the cylinder. We also see how the piston itself is cooling while it is compressing the a/f mixture in the crankcase. Poor circulation on the underside of the piston should (in my brain damaged mind) at least show some indication on the wash pattern/coloring of the piston. If the top of the piston is a fairly uniform color with a fairly uniform carbon pattern we understand that the top of the piston is basically the same temperature all the way across. If only the exhaust side of the piston is darker in color with a carbon “footprint” then we know that the exhaust side of the piston is much hotter than the intake side.

What if there is carbon build up behind the rings? To me that would indicate the piston is quite hot and not cooling properly. I would also venture to guess the ring end gap is extensive and allowing TOO much a/f mixture in behind it: either burnt/scavenged mixture or unburnt. I have been taught that the rings also act as a ‘heat sink’ for the piston, transferring heat from the piston to the cylinder.

Am I off base here?

 

[JohnnyBlade]

Looks like the left opens 3 or 4° earlier. Or the right side is more restricted down in the lowers

As bad as the grinding looks when u shove a ring down with a piston they r opening at the same time. I think its the lowers that wer super restricting. New look. Instead of grindin the bearing cup I raised the lower transfer wall about 3/16" or so and blended

 

[usmcbuckwild]

As bad as the grinding looks when u shove a ring down with a piston they r opening at the same time. I think its the lowers that wer super restricting. New look. Instead of grindin the bearing cup I raised the lower transfer wall about 3/16" or so and blended

If the lowers aren’t even and mirror images of each other than that would result in different pressures and flow through the transfers resulting in different flow patterns into the cylinder; directly affecting the wash pattern.

A caveat to this would be the Echo saws like the 2511. It has 2 very different sized lower transfers in non-symmetrical locations and complimentary uppers of different sizes also in non-symmetrical locations. I’ll be honest; I haven’t look at the wash pattern on one of the Echo pistons.

 

[JohnnyBlade]

Id say the lowers r real close now to symmetrical. Ill test it this sunday and see if i made any gains or not. The saw was ballz before. The lowers almost closed off at BdC. Best description of gap would be 1/1/2 toothpicks width. I actually was told by @StuntCockWelder to leave it alone tonite
Ill never know if i dont try. Its just a AM top end. Good tester. When im happy ill do the same with an OEM. If im not happy ill get another AM and do it again.

 

[Basher]

First hybrid built back around 2008, had enough run time the rings started out with .009 ring end gap, had .030 top, .027 bottom, was time for a re ring, not bad eh.

 

[Basher]

Cylinder,

 

[usmcbuckwild]

View attachment 175473 First hybrid built back around 2008, had enough run time the rings started out with .009 ring end gap, had .030 top, .027 bottom, was time for a re ring, not bad eh.

I’m no expert, but to me that looks nice and even. How did the saw run?

 

[Basher]

In humble opinion it ran great, it made me a believer in the hybrids after I ported it and ran it for 10 plus tanks of fuel it almost took over my soft spot for my 044`s. I have built 5 more since that first one that although run very strong they don`t take anything away from my first. The first one was built on an original 10mm chassis, with a little clearancing a 12 mm crank went in and a 046 P&C grafted on. Also I was plesantly surprised at how clean this engine burned over the long time it has run.

 

[bwalker]

I try to clock all my plugs; it was ingrained in me from a young age. The cylinder design dictates where the ground strap SHOULD be located for maximum efficiency of the spark to trigger the flame kernel and not interfere with its expansion.

There is probably a reason why some cylinders are designed with an angle to the spark plug hole and the actual spark plug tip being placed in a very specific location at a specific depth. I’m not saying specifically 2 stroke engines, but why wouldn’t that same thought process work in these engines.

In regards to reading the piston; its already been proven in this (and other) thread that there is a gross amount of information that can be accumulated from the wash pattern left on the piston. We all know that you can tell quite a bit from a piece of metal by the colors it displays. I believe the same can be said for the piston. If we have carbon build up from heat on the piston, we can narrow down hotter locations inside the cylinder. We also see how the piston itself is cooling while it is compressing the a/f mixture in the crankcase. Poor circulation on the underside of the piston should (in my brain damaged mind) at least show some indication on the wash pattern/coloring of the piston. If the top of the piston is a fairly uniform color with a fairly uniform carbon pattern we understand that the top of the piston is basically the same temperature all the way across. If only the exhaust side of the piston is darker in color with a carbon “footprint” then we know that the exhaust side of the piston is much hotter than the intake side.

What if there is carbon build up behind the rings? To me that would indicate the piston is quite hot and not cooling properly. I would also venture to guess the ring end gap is extensive and allowing TOO much a/f mixture in behind it: either burnt/scavenged mixture or unburnt. I have been taught that the rings also act as a ‘heat sink’ for the piston, transferring heat from the piston to the cylinder.

Am I off base here?

I never found plug indexing did anything and not for lack of testing.
Your not wrong on the role of the piston ring.