Porting!

[tubes380]

not if u are using an 125cc motor. lifan BVH are only good in big bores no good in the 125cc motor

i think you will find that mack is correct, he usually is,
i also think the lifan bvh is better, from what i have seen and read the jialing heads are really hard to get to the same standards that you can with a lifan head

 

[ducar.r.spec]

i think you will find that mack is correct, he usually is,
i also think the lifan bvh is better, from what i have seen and read the jialing heads are really hard to get to the same standards that you can with a lifan head

yeah the ling heads are bloody hopeless
i have 1 here in my shed and u can almost cover the valves with ur thumb
ill post pics side by side with 1 of my bvh's

 

[Mack]

from what i have seen and read the jialing heads are really hard to get to the same standards that you can with a lifan head

it is a physical impossibility to get them to the same standards...

 

[MasterSpoon]

while we are on the topic of porting thought I should ask what grinding / cutting bits most of you guys use?

I decided it was time to start to play with porting stuff the other day and opened up, cleaned and partially smoothed a alloy intake manifold the other day and put some decent wear on my grinding stones (Silicon Carbide stones I think). I am looking at buying some more gear but am unsure if I should get more of these stones as they worked fairly well but just wore out quicker then I had hoped or if something like Carbide Burs Cutting Tools
would be much better suited and should last.

I have used normal carbide burs before and they do tend to clog up fairly easily with alloy but a quick once over with a wire wheel and they are like new again.

 

[corey58]

it is a physical impossibility to get them to the same standards...

yer it would be but i never use and BVH cos they no good on an 125 and gives less performance so dont get to court up in the moment

and im sure of this cos flow benchers are more right the mack in his shed wif his die grinder

 

[Mack]

If you have a dremel get the 60 grit sanding rolls. They'll chew through alloy very fast and leave the finish you want. Save the stones only for grinding down the steel guides.

 

[MasterSpoon]

fair enough
how do you normally go about going around bends like in intake manifolds? The straight bit was easy.. but the bend was a bit more of a challenge to get it down how I wanted it. Wasn't helpful to find out that the manifold didn't even fit in the end..... ohh well needed the experience

 

[Mack]

yer it would be but i never use and BVH cos they no good on an 125 and gives less performance so dont get to court up in the moment

and im sure of this cos flow benchers are more right the mack in his shed wif his die grinder

So u droped 5k on daytona head hoping and wood flow less so you can build big HP 125???
I'm confussed...I got all rong, I better stop wif 30/24 valve Lifan heds....

 

[Mack]

the sanding roll will just easy go round the bend you will see. Finish the bend by hand to make perfect. You will feel imperfections easily with your finger.

 

[corey58]

i did this befor i got mi 119cc and the only reason i didnt use an BVH was becase there no good in and 125cc motor. '

also i didnt make and high HP BVH motor was because i race in an 125cc class and wat the point in cheating it jst no fun....

 

[Mack]

yer u mustav misundastand me cause wot i say is ...u sayd big flow no gud on 125, but u put daytona on ...confussed mor now

 

[MasterSpoon]

hahahahhahaha
I absolutely pissed myself reading that Mack
I could never really understand Corey and most of the time just guessed what he was saying, but don't tell me you are going the same way, who will I turn to for help now?

 

[corey58]

they daytona can handle more air it run an 14:1 comprestion ratio and the values in it are not big at all i thin they like 21/19 not sure but.

and the first thing c'mon man u cant compare an $10000 jap motor built for racing only to an $300 ish motor use for evey day life

 

[Mack]

Ok. Your valves are smaller, but there are TWO of each of them! I give up...

 

[ducar.r.spec]

yer it would be but i never use and BVH cos they no good on an 125 and gives less performance so dont get to court up in the moment

and im sure of this cos flow benchers are more right the mack in his shed wif his die grinder

flow benches are utter bullshit and are incorrect to tell u the truth
quoted from mototuneusa.com:
The Magical Myth of Flowbench - Porting

Once upon a time...
The flowbench is a machine that measures the airflow through the ports by sucking air thru like a vacuum cleaner. The vacuum gauges on the bench actually measure the resistance to the flow thru the ports, and the result is converted into CFM. That means "how many Cubic Feet of air will flow through the port per Minute."




Anyone who buys a flowbench and a dremel tool is "qualified" to flowbench - port heads. The Superflow flowbench owner's manual says that:

" For every 1 CFM of increase in intake flow,
you'll gain .43 horsepower. "

If you want more water to flow through a pipe, just make the pipe bigger.
There's something wrong with this though.


--------------------------------------------------------------------------------
It's easy to understand why so many people automatically think Flowbench - Porting, or "more is better" is a way to improve power.
,
Without closer examination,
it seems quite logical.

Okay, Let's examine it a little closer !!

We were all taught to think of a 4 stroke engine by the traditional textbook explanation of Intake, Compression, Power & Exhaust.

Textbooks and magazines achieve a sort of instant credibility that comes from the association with $$.

Example:
"This source must be right ... after all, there's obviously
some big money behind it ..."

Because of this association, the vast majority of people never question the things they learn in school, or read in mainstream publications.

In the last issue of Power News you learned to think of a four stroke engine in a whole new way... 8 Phases !!

In the 8 phase engine article,
you'll remember that the intake "stroke"
actually consists of 3 phases.
( Overlap, Suction and Charging. )




Uh - Oh ...
It turns out that a flowbench measures the least
important aspect of intake cycle efficiency !!


Stock Yamaha R1 Intake Port
It's true !!
When you stop to think about it, a
flowbench only measures the efficiency
of the "suction phase".

That's not the right
thing to measure.

Why ??
Because, it doesn't matter how well
the cylinder is filled at that point in
the intake cycle !


What ... that sounds crazy !!!
It's 100% true ... it's simply a matter of the sequence of events ! The success of the last event, the charging phase, determines the success of the entire intake process.

What happens when a low velocity port fills the cylinder really well, but too early ?? The result is a slower intake charge that stops flowing into the cylinder. Then some of the charge gets pushed back out of the cylinder and into the port as the piston returns up the bore during the intake charging phase. The gain in flow doesn't offset the loss in port velocity

 

[corey58]

yes.....
so is that y they still using them in drag raceing??

 

[Chooky44]

hey ppl... does anyone know if i could put a 25mm carbie on my Lifan 125 super motor with out having to dick around... or even 30mm

 

[ducar.r.spec]

yes.....
so is that y they still using them in drag raceing??

is ur pitbike a drag car?

 

[ASR Rider]

haha got him there

 

[bigd]

question: i just took off my intake manifold and polished it, was just wondering if there is any point in polishing it if your not going to polish the intake in the head ? (im just not too confident in removing the head, valves etc)