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Heavy Oil Saw

The “Other” 261 Cylinder

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In another post I mentioned having another cylinder for the saw I’m “building”, and that I was worried about some damage I’d noticed on it. Is this salvageable or sling it in the junk with other parts I’ve already renewed.

Here’s the exhaust port

d48635b9cc4b8853a56e748f6e936b94.jpg

And this is a transfer I believe

55c9cb2adee4718b5b34c5017b8a7105.jpg

 

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Job to tell from the pics , its mostly reflection . A couple of small lumps out of the inner edge of the ports ? 

Edited by Stubby

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2937866d06b111cc8f4ae5f28735b2f9.jpg
Is that any better? My opinion is she’s not got any life left in her. Need better lighting in the garage, in the kitchen it’s clear as day the Nikasil is ruined and a chip missing between the transfers.

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18 minutes ago, Heavy Oil Saw said:

2937866d06b111cc8f4ae5f28735b2f9.jpg
Is that any better? My opinion is she’s not got any life left in her. Need better lighting in the garage, in the kitchen it’s clear as day the Nikasil is ruined and a chip missing between the transfers.

Ok . Your call . I cant really tell about the coating . I can see what looks like some light scoring but .... if you can see worse ....

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That isn't good, looks like either a ring has failed, a foreign body has entered the carb or the big end has failed which is the most likely. When the big end cage cracks and breaks up, it flicks bits of white metal through the engine causing this sort of damage.

That damage has bruised those ports, the lower "Transfer" is in fact the strato clean air port, the two top ones are transfers.

Personally I would scrap this one, the previous one looked much sweeter.

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That isn't good, looks like either a ring has failed, a foreign body has entered the carb or the big end has failed which is the most likely. When the big end cage cracks and breaks up, it flicks bits of white metal through the engine causing this sort of damage.
That damage has bruised those ports, the lower "Transfer" is in fact the strato clean air port, the two top ones are transfers.
Personally I would scrap this one, the previous one looked much sweeter.

Your right, looks like it was an internal problem, and metal was dragged around, it was hard enough to chip the cylinder anyway.
Cheers for pointing out the different transfers, I’m at a loss at which is which. Top allows in fuel/air mix and lower is the Strato fresh air (is that the air blower/supercharger in my terminology?). Used to two stroke diesels myself.

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Strato is to clear the cylinder before the new fuel charge is drawn in so you get cleaner combustion. 

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Divots in the cylinder surface are one thing; bumps on the running surface are another kettle of fish entirely. Some of that damage is going to cause a few bumps for the piston and rings to run over.

I'd be surprised if you could hone it round without going through the bore coating.

 

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Strato is to clear the cylinder before the new fuel charge is drawn in so you get cleaner combustion. 

The supercharger/scavenger blower on a 2 stroke diesel clears the cylinder for a fresh charge, as well as feed air for the combustion stage, so to speak. If my days in classroom are to be remembered.

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20 hours ago, peatff said:

Strato is to clear the cylinder before the new fuel charge is drawn in so you get cleaner combustion. 

 

 

Sort of; it makes a cleaner exhaust as less unburnt fuel gets past before the exhaust port closes, combustion takes place after that.

18 hours ago, Heavy Oil Saw said:


The supercharger/scavenger blower on a 2 stroke diesel clears the cylinder for a fresh charge, as well as feed air for the combustion stage, so to speak. If my days in classroom are to be remembered.

Yes and the diesel has the advantage that the fuel is only injected after the inlet and exhaust are closed. With a conventional two stroke the piston descending on the power/exhaust stroke scavenges the fuel-oil mix from the crankcase and pushes it up the transfer port into the cylinder. some goes directly through the exhaust port.

 

What the stratified porting aims to do is allow neat air directly, under the piston, through  the new ports in the cylinder and into the transfer ports without going into the crankcase. Then as the piston descends this neat air is the first into the cylinder followed by the fuel and air from the crankcase.

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