Planet Minis

azextreme

Have any of you out there tried to HV porting on these small heads vs. the norm of hogging out the ports.

cyclerider57

Don't be fooled by different names of porting. Porting is all about getting quantity and quality charge through the head and into the combustion chamber. Then doing what is necessary to keep it in place until it needs to be extracted. Proper porting keeps the port as small as possible while still providing the needed flow for the application. There are ways to trick the flow into thinking the port is straighter, bigger, smaller, etc. It's a balance. Anyone that says high velocity porting is the only way to go is an idiot. Anyone that says making it big is the only way to create power is an equal idiot.

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azextreme

Yes I understand what you are saying but I have used hv on my 660 stock bore raptor @ 69rwhp from a baseline of 33wrhp it has beat several 720 out there to include 720 built by the same builder but with the norm hogged out porting. I'm just curious if somebody has spent the time to due this type of porting on these small engines?? also cyl57 do you ever use epoxy on your porting or just shaping what is there??

Kurlon

You just answered yourself. 'Just hogging it out' isn't good porting, as demonstrated by your raptor comparison.

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azextreme

well I sould have went on the say we also tried it on my 770 stroker drag raptor and it was better to have the hogged out porting then the hv??? also motoman wih the crotch rockets are getting more power with hv then hogged out??

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iridenaked14

Yeah if you "hog it out" it creates all kinds of terrible turbulence, and flow confusion, which can actually create a dicrease of power/ poor power delivery/poor throttle response. What I look for high veloticy while creating a smoother intake delivery and increasing the amount that can go through the valve at the same time. I dont do any porting on the exhaust side because Im not quite sure how it should flow (any pointers?).

cyclerider57

It's shape... not size. Yes, I use epox when needed. The "high velocity porting" is a myth of the port world. Making a port smaller does not increase performance unless the port started to large OR unless it is filled in very specific areas where flow is dead. Part of the reason this "motoman" increased performance by filling in the port on the street bike was because it improved the shape dramatically. He easily could be entirely too small for that engine BUT too small is better than too big as well as the fact that the filling in created a flat short turn radius. This evens out the pressure distribution through the ports turn because the lower moving flow along the short turn creates a higher pressure area that tries to separate from the port wall to early and wants to join the high velocity, low pressure flow along the ports long side flow.

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iridenaked14

Man I wish im as knowledgable as y'all when I reach y'all's age.
Wow a word that requires 2 apostophes(yes I know its not techinically a word.)

HACKMUNCH

remember motoman's heads he shows are all mutivalve intakes, minis are not and that is one reason why it does not work properly on a single valve intake track.

Pat Farsole

What people refer to as "velocity" porting - is when they try different port shape alterations using plasticine/clay to build up certain areas (ie port floor ) and discover (on the flow bench) that they can increase the velocity without losing the cfm of flow by replacing the clay with weld metal or epoxy .

The proper name would be "correction" porting and that's what motoman is basically doing . Sometimes a port can be too big or poorly shaped and angled as stock so added power can be found by altering and reshaping things . Velocity = throttle response and punch - hog a port out too big and you end up with a boggy engine that won't pull the head off a match stick .

Here's some info with porting ideas on pitbike heads :

Mini Dirt Bikes & Pit Bikes Forum : MiniRiders.com.au - Porting!

BBR welds up the port floor on DOHC Daytona heads so even the most expensive heads can have poorly designed ports :[QUOTE : Porting the head and welding and reshaping the port floors resulted in an additional two ponies and a boosted rev range.]

2006 Title-Winning BBR 119 Test - MotorcycleUSA.com

cyclerider57

Motoman doesn't talk about shapes. He just insists that making the ports smaller is better. That is what HE means when he talks about "velocity porting". By that theory he should go even smaller to really take the fluid flow supersonic.

That first link is a good collection of things that have been said on Planet Minis in various threads. Even the pictures come from Planet Minis threads. Good to see someone took the time to collect everyones ideas and put them in one place as single thought. Anyway...

It's good to see him say that. Especially considering I have proof that it is false... along with the fact that they have even been quoted by members from phone calls stating that their klx engines put down 24+hp. Interesting.

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