Author Topic: Port timing.  (Read 883 times)

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Offline Al Smith

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Re: Port timing.
« Reply #30 on: February 16, 2013, 07:43:25 pm »
You know come to think about it if you want 25 thou all you need to do is get a set of micrometers and start measuring paper thickness .Most printer paper is a tad less than 3 thou ,Some is close to 5 thou .An old fashion IBM type punch card is 7 thou .Lots of possibilities here .

Online jmester

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Re: Port timing.
« Reply #31 on: February 16, 2013, 07:47:59 pm »
I measured the gasket at .020 that came off the saw. Have a new one on the way. Will have to measure it to make sure. Is your .015 mill spec with or with out a gasket. I might check out some different stuff. I have been saving some different thickness of paper and card stock for a while.
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Online jmester

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Re: Port timing.
« Reply #32 on: February 16, 2013, 07:56:11 pm »
I just found a index card that is .007 thickness. Should give me a squish of .027 which I can live with. I guess now I need to work on my porting work.
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Online jmester

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Re: Port timing.
« Reply #33 on: February 17, 2013, 08:26:18 pm »
Will you get an accurate squish reading if the rings are removed. Or because the piston rocks back and forth it gives you the wrong reading. I ask because, I cut out my index card gasket of .007 thickness. And bolted the cylinder back up and got a squish of .035. It should be around .027 now with removing the factory base. That measured .020.
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Offline aclarke

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Re: Port timing.
« Reply #34 on: February 17, 2013, 08:53:33 pm »
Put the solder at 90 degrees to exhaust.  I.e. if exhaust is 12:00 put the solder at 9:00 and 3:00  the rocking is minimized at the axis

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Re: Port timing.
« Reply #35 on: February 17, 2013, 08:57:59 pm »
So the rocking does have an effect. I will try it  that way and see what I get.
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Offline Al Smith

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Re: Port timing.
« Reply #36 on: February 17, 2013, 09:10:15 pm »
You have to remember two things .First it's a hemi domed piston plus it's a off set chamber .You're going to have to get that solder where it hits the machined face  around  the chamber pretty square which is going to be tough being off set and a rounded surface of the piston face.

That same deal I might add is why and how I screwed up cutting down the base of an 038 Av and made a head knocker out of it which I had to correct with a thicker gasket .The whole concept  of what I just said had completely slipped my mind when I made my preliminary mesurements .Chit happens.


While on the subject I'm not certain if the chamber is milled perpediculer to the bore or angled .You could probabley check it with a depth micrometer from the cylinder base .Geeze what a fine kettle of fish this is .
.

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Re: Port timing.
« Reply #37 on: February 17, 2013, 09:14:28 pm »
I will check it in a couple of different places tomorrow and see what I get.
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Offline man of stihl

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Re: Port timing.
« Reply #38 on: February 18, 2013, 08:42:19 pm »
This is how i check squish.
Ron

Offline Al Smith

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Re: Port timing.
« Reply #39 on: February 18, 2013, 08:58:03 pm »
Well geeze you usually knock the carbon off first . ;D

I've been racking my brain on this hemi domed piston business becuse it would not be the same with an offset combustion chamber .About the only way or one way might be to squeeze wax and measure with a  good set of calipers from the piston skirt .

I don't know if it would work or not .You'd have to have the piston face clean enough the wax would stick and oil the head deck so it wouldn't stick .

Macdizzy mentioned using some kind  of wax or clay but exactly what kind or how to slips my mind .

 

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