Chainsaw Porting Theory

[Mastermind]

I can see a restrictive muffler playing hell with transfer pressure. Good answer Joey.

I'm gonna go a little further and suggest that more blowdown time would be needed with those stopped up cans.....

 

[Mastermind]

Both

Repped.

 

[jmssaws]

I guess I could have not noticed it but porting them you think I'll would have.

 

[Moparmyway]

I can see a restrictive muffler playing hell with transfer pressure. Good answer Joey.

I'm gonna go a little further and suggest that more blowdown time would be needed with those stopped up cans.....

Come to think of it, that old 046 did have a stock, small opening in the muffler too

 

[jmssaws]

I ported a 026 yesterday that the exhaust was about carbon'd shut and the transfers were shiny and clean.

I think if it's filling plum to the lowers it can't run very good can it?

 

[drf256]

I'm thinking (guessing) it's Coking from heat and not true combusted material from the chamber that far down.

Blair had a nice pressure curve for transfer vs. crank degrees in a chainsaw at 9600 rpm. There's some reversion, but the graph doesnt show enough to be backfilling that far down.

Maybe at decelleration?

The graph is in this thread in an earlier post i made.

 

[merc_man]

I wish I had something to add. Seems like everyday I'm learning something on this site.


Sent from my iPhone using Tapatalk

And it seems for everything ya learn, ya go back ten more steps.
Thers a lot of info.

Sent from my SGH-I747M using Tapatalk

 

[czar800]

I've not had nearly the number of saw a part some of you guys have and yet to see discoloration like that. That said its real hard to believe the discoloration in the lowers is from backfilling.

I could see the possibility a saw in need of a set of rings or like Al said its from heat/over heated saw.

 

[jmssaws]

I'm thinking (guessing) it's Coking from heat and not true combusted material from the chamber that far down.

Blair had a nice pressure curve for transfer vs. crank degrees in a chainsaw at 9600 rpm. There's some reversion, but the graph doesnt show enough to be backfilling that far down.

Maybe at decelleration?

The graph is in this thread in an earlier post i made.

I agree doc,I don't know how it could run well with exhaust back that far.

 

[jmssaws]

I'm thinking (guessing) it's Coking from heat and not true combusted material from the chamber that far down.

Blair had a nice pressure curve for transfer vs. crank degrees in a chainsaw at 9600 rpm. There's some reversion, but the graph doesnt show enough to be backfilling that far down.

Maybe at decelleration?

The graph is in this thread in an earlier post i made.

The 80's are gone doc,we're not Coking anymore.

 

[huskihl]

I agree doc,I don't know how it could run well with exhaust back that far.

I agree too. I'd bet if one of those saws of Joey's was put back into service with either (or both) a good muffler mod and use an oil that wasn't known for leaving carbon deposits, that the carbon wouldn't be in the lowers.
But I also have no doubt that some exhaust gets pushed into the transfers, and then back out above the piston. And some fresh charge makes it out the exhaust, and is supposed to get sucked back in and get burned....all in perfect harmony

 

[quietfly]

The 80's are gone doc,we're not Coking anymore.

speak for yourself, according to my town PD coke is making a come back .

 

[drf256]

The 80's are gone doc,we're not Coking anymore.

Maybe not in MO, J.

 

[Ironworker]

The minute you think you know it all, it's over for you. An open mind and free discussion is where it's at.

Anyone familiar with the Citibank building in NYC? The one with the 45* square roof?

The brightest and best architects designed it. They completed the project and stood gleaming at their accomplishment.

An 18 yo architecture student called the head architect and told him "your building is gonna fall down sir". They actually pulled this kid in and listened to his theory. They opened every wall, where needed, and added bolts to the welded beams where needed. The student was right.

So anyone can come up with a better idea because we all see things differently.

So let's carry on this discussion freely

They actually just welded everything, but close enough.

 

[Al Smith]

I've only seen that black chit inside of one saw .An abused 034 AV that had literally sucked the flock right out of the air filter .All that was left were the wires that held the flocking .

It still ran and was only shelved when it blew a clutch shoe and the chain never stopped turning .It's a long story .
My thoughts were it was a combination of about a pick up truck full of ingested dust combined with plugged up fins and fan housing which combined with blow by of the loose piston caused it to pyrolite the mixture and caused in essence petrolium coke formation .I fixed it with a new piston and a donor 036 cylinder .

 

[XP_Slinger]

Repped.

Don't know what that means. Even looked for it in a dictionary before I made myself look stupid by posting this...lol. guessing it means "owned"? If so, many more times coming

 

[XP_Slinger]

I like the restrictive muffler point. What about ring blow by? Seems a tired ring would let exhaust gases blow by a bit and give you some carbon in places it doesn't belong. Just a thought.

 

[jmssaws]

If it gets past the rings it would pump it back through the transfers.

 

[czar800]

If it gets past the rings it would pump it back through the transfers.

Yes it would but maybe it cools off a little and leaves a stain?

 

[jmssaws]

That's what I'm saying, if it gets past the rings it would pump it back through the transfers and leave residue.