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Old 10-30-2004, 07:49 PM
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Default Porting Who has done there own?

     

Who has had a go at porting there own head?
Is it similar to porting out the exhaust ports on a car to gasket match the exhaust?
The KTM 200 has a flat section on the exhaust that restricts exhaust flow into the pipe!
Just begging to be cleaned out and polished!
What effect will porting out the exhaust port, matching it to the pipe and polishing have on the the bikes power?
This thing has already been knife edged and roughed up on the inlet side of things!
That alone gave it much more top end!
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Old 10-30-2004, 07:58 PM
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Default Re: Porting Who has done there own?

There is much more inolved in porting a head than most would think. Knife edging and texturing will accomplish little if anything.
Maybe I can see if I can get RHC to post a little on the subject.
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Old 10-30-2004, 08:01 PM
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Default Re: Porting Who has done there own?

ya i would like to know too.
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Old 10-30-2004, 08:29 PM
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Default Re: Porting Who has done there own?

What ever you do dont match the ex port to the pipe and do not remove the step on the bottom of the ex port .the small port not only helps velocity but it also helps prevent ex reversion .i have had the oportunity to test ex ports that are open to the pipe on the short side when testing with a flowbench and probing the port you will find on some ports that the layers of air are actually moving back towards the cylinder and putting ex gases back into your fresh incoming charge i call this the built in EGR valve you really dont want this on your race engine .also matching the port and valve seat areas can end up making the throat to valve relation ship to large and this will cost you low lift flow and since your cam has your valves at the lower lifts longer than it does at peak lift this can cost you hp .also sharpening port dividers does not nessarly make them flow better if you look down into the manifold of a stock car you will see where they have built the dividers up with epoxy to get a large radius and then tapering to a thinner section like a tear drop i have proved this on 2 strokes on the flow bench .hows that tryce
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Old 10-30-2004, 11:18 PM
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Default Re: Porting Who has done there own?

where two strokes are concerned lots of us used to knife edge the dividers on the transfer ports. we thought that it would increase flow, seemed to make sense, lots of mail off port grinders did it, and some of the magazines endorsed it. in reality those of us that tried it lost low end in particular by decreasing our primary compression. since it ran worse on bottom than top, we all claimed we had moved the power band up. as long as we raced eachother on similarly butchered bikes we were "convinced". of course if you ran up against a decent stocker your tank emblems got sucked off. it has gotten even harder for the home engine builder to improve on stock without at least having some specs, drawings, and diagrams from someone who has found more power by porting. then you need the expertise to execute as they did.
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Old 10-31-2004, 06:26 AM
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Default Re: Porting Who has done there own?

I would have thought that getting the exhaust gases into the pipe would be a better mod!
RHC is ex reversion a back pressure wave!
The dividers on the transfer ports have been knife edged and the result was definately an increase in top end! An improvement I liked.
Is a compression increase the answer to more bottom end?
I have found the 200 exc could use just a bit more bottom end but not much more!
Standard they are pretty good little bikes!
Guys I think I need more info on the subject as I think there must be more power locked up inside these little 2 smokers!
Whats the best way to get 10% more out of them?
Bigger bore?
If a smaller outlet would increase air flow can you reduce the outlet size with a plate? You could have different sized plates!
Kinda like an orifice plate in a pipe for flow measurement!
Just an idea! (Don't know if its a good one)
You kinda want something to increase the power abit (besides race fuel) thats cheap and changable!
I know different heads are one way!
Any others?
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Old 10-31-2004, 06:43 AM
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Default Re: Porting Who has done there own?

Guys Ive just had a look on the net at porting and thats enough for me I'm leaving mine alone!
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Old 10-31-2004, 06:53 AM
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Default Re: Porting Who has done there own?

Thanks Ron...You da man!
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Old 01-28-2011, 07:50 AM
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ok so in other words if you wipe out and dent your pipe your bike should run better because it has more resitance or equal to a smaller hole?come on there is someone out there that has done porting and has an improvement.
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Old 01-28-2011, 10:42 AM
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Lots of old threads being dug up lately.... this one is 7 yrs old but good info.

Try searching here or other sites for Eric Gorr, he is arguably the foremost porting guru.


Quote:
Originally Posted by hellhound View Post
ok so in other words if you wipe out and dent your pipe your bike should run better because it has more resitance or equal to a smaller hole?come on there is someone out there that has done porting and has an improvement.
It all depends where you dent your 2 stroke pipe. The science of a 2 stroke pipe is very interesting, again tons of stuff out there on it if you search.
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Old 01-28-2011, 10:47 AM
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I think that it was made clear that some of us have tried it and gotten some good and some bad results. Have you got a specific engine in mind?

On the pipe dents,,,if you have one to waste, go beat some dents in it and see how far you have to go to actually get a difference. The dimension that makes the biggest difference i have found is the overall length, followed by the length of the different sections.
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Old 01-31-2011, 07:20 PM
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go register and read this thread...

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