Porting knowledge

O___o
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O___o 11/3/2014 9:01am
11/3/2014 9:01am
reded wrote:
One guy does the work and gathers the numbers. They then send his port job to the magazines for tests and it comes back with rave...
One guy does the work and gathers the numbers. They then send his port job to the magazines for tests and it comes back with rave reviews and the orders start rolling in. Then they hire 4 flunkies to grind out the customers cylinders using the numbers provided. When the flunkies get done it looks like they attacked it with a hatchet and a hacksaw.

Having said that, I had a '95 KX250 cylinder ported by FMF back when and it couldn't have been any more beautiful. Ran like a scalded dog too!
O___o wrote:
Not 100% sure but I think that's when Varner was an FMF employee.
slipdog wrote:
100% it was Varner... Not sure when he became an employee, '95-'96ish, but they sub'd the porting to him for years before just bringing him in...
100% it was Varner...

Not sure when he became an employee, '95-'96ish, but they sub'd the porting to him for years before just bringing him in house.
Figured.
reded
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reded 11/3/2014 9:15am
11/3/2014 9:15am
Thinking back on it, I believe the specs were "supposedly" the same as what Ty Davis was using at the time. They even had a special pipe designed for the porting specs. I didn't buy the pipe as I didn't feel it was necessary after riding it with the FMF pipe that was already on the bike.
hvaughn88
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hvaughn88 11/3/2014 9:52am
11/3/2014 9:52am
hvaughn88 wrote:
I know next to nothing about porting, etc. Let me put that out there first. My question, though, is after hearing some people mention getting work...
I know next to nothing about porting, etc. Let me put that out there first. My question, though, is after hearing some people mention getting work done by the big guys (not naming names) and it being a cluster, it makes me wonder how these companies are doing as much work as they are. Is it a situation where they started out small and did great work, and then the quality diminished as they grew? Or is situations where a customer like myself, who doesn't know much, just assumes that what they are getting done is really what they need?
reded wrote:
One guy does the work and gathers the numbers. They then send his port job to the magazines for tests and it comes back with rave...
One guy does the work and gathers the numbers. They then send his port job to the magazines for tests and it comes back with rave reviews and the orders start rolling in. Then they hire 4 flunkies to grind out the customers cylinders using the numbers provided. When the flunkies get done it looks like they attacked it with a hatchet and a hacksaw.

Having said that, I had a '95 KX250 cylinder ported by FMF back when and it couldn't have been any more beautiful. Ran like a scalded dog too!
damn, that's pretty disappointing.
YZ125H1
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YZ125H1 11/3/2014 10:06am
11/3/2014 10:06am
Honestly, I would deal with a local engine builder if he has decent reviews. Much rather prefer someone you can go to in person than sending it off to a bigger place. Problem with porting is finding an exhaust that will work good with the porting. If you are going for porting might as well go the whole 9 yards and get a race engine built and run only race gas IMO. Unless you just are not happy with how the stock powerband is.

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Tracktor
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Tracktor 11/3/2014 10:24am
11/3/2014 10:24am
newmann wrote:
I spent $500.00 12 years ago getting my 74 CR250 ported. Of course that included polishing and matching the carb to a billet intake manifold, manifold...
I spent $500.00 12 years ago getting my 74 CR250 ported. Of course that included polishing and matching the carb to a billet intake manifold, manifold to cylinder, cases opened and port matched to transfers, exhaust port and manifold matched and polished as well as cutting and reshaping the head. Had to have a pipe built to match the engine mods for another chunk of change. She's a fire breather though. Smile

Bummer that the guy turned out to be a bit of a flake and has yet to return some other pieces I sent him ten years ago....

I sure wish there was someone out there who could do something similar on a 74/75 CR125 engine for me. Slippy???
Arlan Lehman at LED Performance is the guy. He is a total vintage nut. Here is a pic of one of his hand coned pipes




1979 MUgen 125 Cylinder-



brocsdad
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brocsdad 11/3/2014 1:11pm
11/3/2014 1:11pm
I was first introduced to Barr’s Competition back in the 90’s when former factory Suzuki rider Steve Childress was running his motors. I was blown away how fast his Suzuki’s were.

Over the last several years I have used Barr’s Competition for my sons 65’s and 85’s and they have been great.

I did have a Varner RM 125 and PC RM 125. The Varner motor had a really strong mid-range but went flat on top and the PC was a little better than stock. Neither ran like the Barr’s 125.

I have heard great things about Tom Morgan Racing and Tomac’s old mechanic Gregg Lynk.

brocsdad
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brocsdad 11/3/2014 1:14pm
11/3/2014 1:14pm
On another note I see a lot of the ported cylinders with the intakes ported and polished.

I have always been told the intake needs to be rough to help mix the fuel coming into the cylinder. I also see where tuners sharpen the bridges and their seems to be controversy over that as well.
slipdog
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slipdog 11/3/2014 2:53pm
11/3/2014 2:53pm Edited Date/Time 11/3/2014 2:54pm
brocsdad wrote:
On another note I see a lot of the ported cylinders with the intakes ported and polished. I have always been told the intake needs to...
On another note I see a lot of the ported cylinders with the intakes ported and polished.

I have always been told the intake needs to be rough to help mix the fuel coming into the cylinder. I also see where tuners sharpen the bridges and their seems to be controversy over that as well.
Knife edging an intake bridge is bad.

Polishing the intake is not good for consistent air/fuel mixture, but not as bad for power as it is made out to be. As a matter of fact I learned from Cosworth F1 engine designer that when designing an engine from the ground up, he doesn't care how you texture the intake tract. He said as long as you get the volume and cross sections correct, the hp numbers will fall into place. I don't polish...
brocsdad
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brocsdad 11/3/2014 2:59pm
11/3/2014 2:59pm Edited Date/Time 11/3/2014 2:59pm
Educate me... Why is it bad to knife the intake?

You could tell where Barr's had changed the port heights and polished the exhaust but the intakes looked stock. No porting marks or knifing and the bike ran great!
O___o
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O___o 11/3/2014 3:00pm
11/3/2014 3:00pm
slipdog wrote:
Knife edging an intake bridge is bad. Polishing the intake is not good for consistent air/fuel mixture, but not as bad for power as it is...
Knife edging an intake bridge is bad.

Polishing the intake is not good for consistent air/fuel mixture, but not as bad for power as it is made out to be. As a matter of fact I learned from Cosworth F1 engine designer that when designing an engine from the ground up, he doesn't care how you texture the intake tract. He said as long as you get the volume and cross sections correct, the hp numbers will fall into place. I don't polish...
The problem is, if you don't polish, Joe-shit the Redneck mini dad doesn't think you did a good job.

Remember ladies, an educated customer is a good customer.
StartedTooLate 11/3/2014 3:01pm
11/3/2014 3:01pm Edited Date/Time 11/3/2014 3:11pm
Crush wrote:
If you've got a KTM Slavens are pretty unreal. The 300 he did for me was ridiculous! So much stronger than the stockers everywhere it was...
If you've got a KTM Slavens are pretty unreal. The 300 he did for me was ridiculous! So much stronger than the stockers everywhere it was like a bore kit....
2 Stroke Beast wrote:
But they only do ktms Im assuming
O___o wrote:
transfers are transfers, port heights are port heights.
Exactly. It seems few carefully read the original post..... To truly understand porting, you have to understand specific port time areas, as described by Blair, as well as expansion chamber design. Change the porting...change the pipe. Most of the comments here have been about exhaust porting and exhaust port heights, which is not what the OP asked about.

Transfer ports are very empirical, so you have to find someone who has a lot experience with your specific motor. Trial and error is the rule on transfers once you have the overall exhaust porting and expansion chamber roughly set. Sometimes you end up improving a motor by making transfer ports SMALLER, or changing angles without really changing transfer timing or size. Sometimes you can make improvements with timing, but that is a lot of work, and often involves ADDING material is some sports...taking it away in others. With regards to transfer timing, blowdown is the key parameter... the degrees of motor rotation from when the exhaust port opens, til the transfers are exposed. This is a key parameter in conjunction with expansion chamber dynamics.
1
slipdog
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slipdog 11/3/2014 3:17pm
11/3/2014 3:17pm
B's Dad, 0_o nailed it when he said most people want to see the bling and assume if it's not bitching looking it must not be a good port job. Eric Gorr gets railed for that a lot, but for the most part he does what's necessary and concentrates on the mechanics of the job. Most modern casting is so good they don't need much help, not like back in the 70's-80's where just a good blueprint made a big difference.

Bridges need a rounded face to create a boundary layer for the a/f mix to flow around, sharp points splitting the flow creates turbulence around the bridge. A perfect example is an airplane wing. The sharp edge points rearward and the front is rounded to create a tear drop shape. If it was the other way the turbulence would break the wing apart.
brocsdad
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brocsdad 11/3/2014 8:46pm
11/3/2014 8:46pm
It seems most of the tuners agree to not knife or sharpen the bridges and prefer it to flow like an airplane wing. As far as leaving the intake ports rough one of the former Kawasaki mechanics and current motor builder said the fuel has already mixed by the time it passes the reeds. He said if you leave the intake rough you get more snap or low end torque. It you smooth the intake it will result in more top end pull or torque at high rpm's.

Outsider
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Outsider 11/3/2014 9:09pm
11/3/2014 9:09pm
I just make sure I've port plenty of pump gas in the 450... not sure if that the ticket but it always goes like hell
41NDT
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41NDT 11/4/2014 3:02am
11/4/2014 3:02am
41NDT wrote:
Send your stuff to JGR you won't regret it.
2 Stroke Beast wrote:
JGR website is a joke in the category in house motor mods there is 2 things listed
Do you want nice pictures or an engine that rips. Don't know about you but I spoke to the shop on this thing called a phone explained some stuff and then sent it to them. The bike pulls to the moon. Hang on you repaired phones well fuck me swinging did they work? Get one and use it the info from one can be life changing. Hugs and kisses Ma Bell
CamP
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CamP 11/4/2014 5:36am
11/4/2014 5:36am Edited Date/Time 11/4/2014 5:36am
slipdog wrote:
B's Dad, 0_o nailed it when he said most people want to see the bling and assume if it's not bitching looking it must not be...
B's Dad, 0_o nailed it when he said most people want to see the bling and assume if it's not bitching looking it must not be a good port job. Eric Gorr gets railed for that a lot, but for the most part he does what's necessary and concentrates on the mechanics of the job. Most modern casting is so good they don't need much help, not like back in the 70's-80's where just a good blueprint made a big difference.

Bridges need a rounded face to create a boundary layer for the a/f mix to flow around, sharp points splitting the flow creates turbulence around the bridge. A perfect example is an airplane wing. The sharp edge points rearward and the front is rounded to create a tear drop shape. If it was the other way the turbulence would break the wing apart.
Yep, a radius leading edge is what you want for clean, turbulence free, air flow when the speeds are sub-sonic. On the other hand, Super sonic air speeds require a knifed leading edge to prevent turbulence.

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