Porting and Port timing - ArcticChat.com - Arctic Cat Forum

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post #1 of 12 Old 02-09-2010, 06:49 PM Thread Starter
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starting to port the 600 zrt jugs. i am experienced with work 4 stroke high power autmotive heads first set of sled jugs. i refuse to purchase templated cause i dont think that thing like this are right.

im going to port match to about .025 to the exhaust flanges and leave then bolted on so they cant be moved. and smother out and slightly enlarge the exhaust side. now the ring support in the center of the port. i have seen a few motors that have large ports and and no ring support. so can i cut this out?

i am going to clean up the intake abit also. but mainly the transfer port i see a 900 hat have about .500 cut off and it was gasket matched.

any tips or pictures?

debating on how to attack the cases.

as for port timing, im not sure how much to raise or widen the ports. hence why im going to double the base gaskets.


pictures or if you wanna talk on the phone would be great. thanks in advance

96 zrt 600 non apv motor
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post #2 of 12 Old 02-09-2010, 07:15 PM
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Just don't polish the intake port, leave it rough! And don't take out the transfer port bridge!

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post #3 of 12 Old 02-09-2010, 07:26 PM
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No offense but;

Are you sure you want to do what you are talking about. Do you really understand what you are talking about?

Porting a two stroke is totally different than doing a four stroke. A template would be a good way to start. Port timing, size and shape of ports, and webbing are nothing to fool with unless you totally understand what goes on inside of a two stroke. Everything going on inside of a two stroke during operation is balanced and interacts with one another. Intake and exhaust strokes over lap one another and are not isolated as in four strokes. As an example of this, when you change exhaust port timing or shape you also effect the flow thru the intake ports. This example is very basic if you do understand how this works you probably understand how intake can effect the unwanted heat producing, horsepower robbing, radicals that live in your expansion chamber when in operation.

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post #4 of 12 Old 02-09-2010, 07:33 PM
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<div class='quotetop'>QUOTE (gapl1953 @ Feb 9 2010, 09:26 PM) <{POST_SNAPBACK}></div>
Quote:
No offense but;

Are you sure you want to do what you are talking about. Do you really understand what you are talking about?

Porting a two stroke is totally different than doing a four stroke. A template would be a good way to start. Port timing, size and shape of ports, and webbing are nothing to fool with unless you totally understand what goes on inside of a two stroke. Everything going on inside of a two stroke during operation is balanced and interacts with one another. Intake and exhaust strokes over lap one another and are not isolated as in four strokes. As an example of this, when you change exhaust port timing or shape you also effect the flow thru the intake ports. This example is very basic if you do understand how this works you probably understand how intake can effect the unwanted heat producing, horsepower robbing, radicals that live in your expansion chamber when in operation.[/b]
Kinda what I was thinking too!

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post #5 of 12 Old 02-09-2010, 07:39 PM
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I believe that if he listens to us and reads between the lines he just might avoid a disaster.
What do ya think!

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post #6 of 12 Old 02-09-2010, 07:45 PM Thread Starter
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i didnt mean polish the intakes. i shape and then go over with 80 grit eastwood rolls.

i didnt touch the tranfer ports yet. but ive seen a few mod engines apart and noticed how they had there's modified and had some conversations about it

as for for the center ring support i decided to thin and roll the inside edge.

i dont want to re engineer the port timing. but from conversations ive had with crankshop they advised me that when they port they normaly raise the exhaust ports
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post #7 of 12 Old 02-09-2010, 08:39 PM
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Ok! Did they happen to tell you how much to raise them? Note; VERY IMPORTANT!!!

Changing the exhaust port timing changes the characteristics of the intake pulse and the timing of the expansion chamber at the same time.

YOU CAN LEAD, AS LONG AS YOU CAN KEEP UP!

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post #8 of 12 Old 02-09-2010, 09:23 PM Thread Starter
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well thats my question. he didnt say how much. another person i was talking to about this that run a mod sugested that i push them up .040 personaly this is the part im concerned about.

so im gonna take the advice to leave the hieghts alone thank you for that. unless someone has a better idea.

im very happy with how the first exhaust is turning out. how are your guys sealing them to cc the ports? was thinking some pepsi bottle and some vaseline. and whats a safe tolerance?

i have spare base gaskets. should i leave the ports and just double them? the heads are already sent out to be cut. would just take more off this way

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post #9 of 12 Old 02-10-2010, 08:28 AM
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The factory coats the exhaust gaskets with high temp red silicone sealant. That's what I use and it works well.
Before the high temp silicone came out I used Prema Tex Aircraft Gasket Seal with good results.

YOU CAN LEAD, AS LONG AS YOU CAN KEEP UP!

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post #10 of 12 Old 02-10-2010, 08:37 AM
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I use the Red High Temp Silicone Gasket sealant. That is what the factory uses. In the past, before the silicones, I have used Perma-Tex Aircraft Gasket Sealant with good results.

If you are interested in learning more about your engine a good place to start is the Dyno Tech link on this web site. They have a great archive of information, with some of the best technical authors you can find anywhere, well worth the cost of a subscription.

YOU CAN LEAD, AS LONG AS YOU CAN KEEP UP!

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