Piston wash patterns

[Ketchup]

Dolly 5100s with intake and exhaust port only, and soda can gasket. Someone told me it looked okay I have no idea. This was after a couple tanks.

View attachment 303272

Never touched a 5100, but doesn’t that look like short circuiting out the exhaust?

 

[Nutball]

Remember Doc had one with a completely clean exhaust that ran very well. I have no idea why many wash patterns have a clean spot right next to the exhaust port.

 

[NightRogue]

The cylinder flange and case are also very restrictive at the transfer lowers.

Totally
I work differently on the lowers

 

[NightRogue]

Remember Doc had one with a completely clean exhaust that ran very well. I have no idea why many wash patterns have a clean spot right next to the exhaust port.

Imo on stock saw the wash pattern is showing scavenging loop is somewhere around 50% charge and 50% exhaust at power rpm or sometimes even lower, when muffler modded and ported it usually goes up to 80~100+%.

Thats why you dont want to go too far with muffler mod, especially when that saw has high CC or BD, to avoid charge escaping out. Exhaust gas in middle is usually hard to impossible to purge out, unless it gets piped and a boost port added. Explains the reason why boost port is recommended to open before secondaries and mains, exhaust gas pocket in the middle moves lazy and needs some "persuasion" to get into the fast moving area

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[mettee]

Pipe saw?

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Not that I know of, but the wash pattern looked like a mustache.

 

[mettee]

Does it have muffler mod?
Looks pretty good to me

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Yeah I made the stock location a bunch bigger.

 

[mettee]

Never touched a 5100, but doesn’t that look like short circuiting out the exhaust?
View attachment 303396

No idea, honestly you would have to tell me.

 

[NightRogue]

Yeah I made the stock location a bunch bigger.

That wash pattern does indicate your muffler opening being a little too big, you should've gained lot on high up and lost a little low down

 

[mettee]

That wash pattern does indicate your muffler opening being a little too big, you should've gained lot on high up and lost a little low down

I put the screen back in you think that might be enough?

I gave the saw to a good friend and he loves it. If it comes back to me for some work I'll check the piston again.

 

[Ketchup]

I would be interested to know if a screen makes a difference.
In general I wouldn’t worry about it. As long as the spent gasses are getting out a little fresh charge going with it shouldn’t make a big difference. The first 346 I did was just max widening and tight squish. It’s been my go-to crane saw for 5 years. It’s not fuel efficient, but is otherwise fantastic.

 

[NightRogue]

I put the screen back in you think that might be enough?

I gave the saw to a good friend and he loves it. If it comes back to me for some work I'll check the piston again.

Its hard to say if it'll run better or not without timed test cut or a dyno run

 

[mettee]

Its hard to say if it'll run better or not without timed test cut or a dyno run

It was slicing and dicing misquite with a 20" full comp 3/8 EXL chain. Couldn't hardly slow it down...

If he brings it to me I'll take a new pick after some more use with the screen in.

 

[Sawrain]

Ran two tanks through a salvaged cylinder on a rebuilt Husky 365, pulled the jug to inspect and found my thumb print.

Think combustion Products stuck to the molykote 111 I use to hold squish checking solder in pace.

First time I have seen it.

 

[Nutball]

stock 9010

 

[Ronie]

From a 660 clone with less than two tanks since install.

 

[huskyboy]

From a 660 clone with less than two tanks since install.
View attachment 307520

Strange

 

[huskyboy]

stock 9010
View attachment 307465

Not bad

 

[Dieselshawn]

January 2020 built Stihl 661. 3 months run time.

Now it’s a dyno mule.

 

[Maintenance Chief]

372xp clone 4 or 5 tanks , ran at least half with stihl ultra but switched to Echo red armor.

 

[Nutball]

Here's an old pic of my stock 394 piston (after a decent amount of milling). I asked about the wash pattern and was told it looked nice and even. The trusted builder who told me that also said if it was uneven it could indicate tansfers on one side opening a tad before the other.
View attachment 139731

This was with Husky XP if we are going down the erl path..

Interesting comparing it to this 395 I found in the artwork thread

Same basic shape, but the carbon is concentrated in different locations.