Author Topic: First try at Port #'s  (Read 499 times)

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Offline Old Iron Logging

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First try at Port #'s
« on: January 16, 2012, 07:29:17 pm »
I think I have my degree wheel set. Here is what I find with my 5000. Exhaust opens at 100 and transfers at 130. Does that give me a blowdown of 30?

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Offline Al Smith

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Re: First try at Port #'s
« Reply #1 on: January 24, 2012, 08:15:56 pm »
Yep .

Offline Al Smith

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Re: First try at Port #'s
« Reply #2 on: January 26, 2012, 09:35:25 pm »
Thinking about that it's probabley why they run so good . Most Stihls have exhaust numbers between 96 and 101 with about 22-26 degree after opening of the transfers  depending .

Then too it depends on how accurately  you use the degree wheel because you can be off a few degrees one way or the other .It's relative  any way depending on the port size and predicted RPMs .

Offline MacLaren

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Re: First try at Port #'s
« Reply #3 on: January 31, 2012, 04:18:10 pm »
Al, is there a way not to be off with the degree wheel?  Please excuse my ignorance on the subject as Ive never ported a saw before.

Offline CASE5854x4

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Re: First try at Port #'s
« Reply #4 on: January 31, 2012, 06:22:53 pm »
The trick is being able to have a clear view of when the piston opens or closes the ports. Like Al said it is not hard to be off a weee bit one way or another.
I struggle with the upper transfers "peeking" through the spark plug hole at an angle  :o Then there is the ex., by using a flashlight through the sparkplug hole, do you measure as soon as the first bit of light slips out & onto the floor of the outlet or when you see it exposed at the crown of the piston ??? If you go with the first sliver method you have to accept that the chamfer on the port is letting the light sneak out.

Steve

Offline Old Iron Logging

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Re: First try at Port #'s
« Reply #5 on: January 31, 2012, 07:11:23 pm »
The stock #'s would be different than the ones posted. Ex has been raised and transfers still stock.

Offline mdavlee .

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Re: First try at Port #'s
« Reply #6 on: January 31, 2012, 07:40:17 pm »
I use the light in the exhaust port and look through the plug hole to get the exhaust timing. Transfers are harder to see through the plug hole.

Offline Cut4fun .

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Re: First try at Port #'s
« Reply #7 on: January 31, 2012, 07:52:08 pm »
How bad do you want to see inside? fiberoptic bore scope  http://www.amazon.com/Pro-Vision-300-Fiberoptic-Borescope/dp/B000U07X6E

Inspect without opening it up to look at crankbearings, cranks, port timing etc.

http://www.youtube.com/watch?v=9HrGcTxOF58
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Offline Al Smith

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Re: First try at Port #'s
« Reply #8 on: January 31, 2012, 09:17:21 pm »
First of all you have to center the wheel on top dead center .The easiest way is to use some type of piston stop .Put it where you think TDC is then rotate it one direction and write down the degrees then rotate it opposite to the stop  and again write them down . If for instance you're 10 degrees one way and 5 the other then set the wheel for 7.5 and check again .When it's equal on both rotations you've found TDC .

Mac Dizzy covers it pretty well if you want to look .

Offline Al Smith

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Re: First try at Port #'s
« Reply #9 on: January 31, 2012, 09:28:50 pm »
Forgot a few points .I use a little LED light about the size of a ball point pen ,brilliant little thing .Always take the measurements in one direction ,the direction of rotation .If you go passed the very point of the port opening ,back it up and approach it again .

I use degrees of rotation starting at zero or TDC .Some like to use before TDC ,after 180 or bottom dead center and it gets damned confusing if you mumble jumble stuff than way .

Some use something like a 4 cycle wheel made by for instance Crane cams .Nothing wrong with them except this too gets confusing to guys like me that use a   360 degree wheel .As long as you know what you have though I guess it really doesn't matter . ;)

 

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