Motomaxx Velocity Stacks (air funnels) - Honda CBR500R Forum : CB500F and CB500X Forums
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post #1 of 10 (permalink) Old 08-25-2016, 09:00 AM Thread Starter
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Motomaxx Velocity Stacks (air funnels)

A few of you have been waiting for this so here are my results after having installed the Motomaxx velocity stacks as found from their Facebook page here.
Refer my hyperlinked signature for listing of other mods done to my bike; individual result will vary depending on level of mods to your bike. Unfortunately for me, this modification did not return a benefit other than a learning experience. Credit to @_Yamato for his contributions and of testing the concepts of velocity stacks, and I recommend reading his post on the subject here. Also a shout out to @Oyabun for his input on the subject also; without the two of you guys for inspiration I don't think this would've eventuated.
So these stacks are a nice bit of kit, milled from solid blocks of billet aluminium.


Side-by-side you can see how there was expectation from the change in shape and height that they would flow better than factory; based on the knowledge that wider means more flow and shorter better for higher rpm power.


Installation is for the more technically minded. It requires removal of knee panels, front fairings, fuel tank, and airbox & throttle bodies (as one). Separating the main halves of the airbox you then just undo three screws for the v'stack housing. The stacks just twist out, and you twist the new ones in; then re-assemble everything back together.

Of note, the ones that I received did have a small 0.5mm lip on the bottom end that required removal using a rotary too. This was notified to the company, so hopefully future versions have this corrected.

I had previously had a run back in July for a base figure. By the time I received the stacks for installation, I had since replaced the tyres due wear. So when the dyno was spun up and we saw that the returned figures were actually less than the base run, there was some concern. So out with the new and back in with the old factory velocity stacks to get a new base line. Comparative dyno graph result below, as you can see, very little difference between factory and aftermarket; like ~1hp or less which can easily be attributed to environmental & other factors.

Be aware however that my bike already being quite modified, that it may be a case it has reached the capable limits of flow. So I'm not saying these stacks are of no benefit, just in the scenario given they did not return desired results. Maybe if my bike had ported and polished heads to compliment the other modifications, that these would then be the key to releasing further potential.

Another key element is that the company has developed these stacks in response to seeing that the factory stacks in many markets have a restrictor plate in place... if looking down the velocity stack looks like the below, you got the restricted version.

Easy, cheap win is to order the factory stacks from another country. In the parts catalogue they are listed as P/N 17251-MGZ-D00 (left) & 17252-MGZ-D00 (right), they also come with a country dependent serial code, U and 2U are for Australia of which being my country I know are unrestricted funnel models. But if you like a bit of bling, or maybe the price plus shipping doesn't work favourable, there's nothing wrong with grabbing a set of the Motomaxx velocity stacks.
If you're interested in this product, simply get in contact with Motomaxx via their Facebook page.

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post #2 of 10 (permalink) Old 08-25-2016, 11:13 AM
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maybe i will give them a try, because i'm not planning to do the cam shaft mod and so on ... and i have to check if i don't have the restricted stacks in the bike too (my guess is i will, because the company is based in the same country as i am and the bike it was developed for was too), so i will check the options, because from what i saw OEM parts in europe are f-ing expensive compared to $ countries example: on US sites the airbox lid is about 6.67$ or so ... on EU sites i found it for 56 ... so yeah
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post #3 of 10 (permalink) Old 08-25-2016, 12:37 PM Thread Starter
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wow that's a ridiculous difference! It's amazing how some items are bad like that. Australia is pretty good for most of items, except the factory add ons like the rear cowl and tyre huger, they're like 3x the price.
I can see why the motomaxx option could very well be the simpler solution for our European brethren.

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post #4 of 10 (permalink) Old 08-25-2016, 08:36 PM
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Did they adjust fueling for the new stacks? Just curious as there is a bit of difference in afr right in the middle that corresponds to the factory stacks outperforming the motomaxx which leads me to believe the bike wanted more fuel in that area.
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post #5 of 10 (permalink) Old 08-25-2016, 08:50 PM Thread Starter
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Originally Posted by JCarrithers View Post
Did they adjust fueling for the new stacks? Just curious as there is a bit of difference in afr right in the middle that corresponds to the factory stacks outperforming the motomaxx which leads me to believe the bike wanted more fuel in that area.
The fuel map was adjusted in both instances for highest power per rpm increment. The different flow characteristics of the stacks yield different power figures from different AFRs, like in the lower rev range the leaner mix returned greater power than the right factory. Still, comparing differences to other map data i got from the multiple runs prior to this, we'd be talking differences in the 1hp range; time-vs-gain not really worth it. Could get the similar improvement between morning and arvo ride or by dropping the kids off in the porcelain bus before the ride

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post #6 of 10 (permalink) Old 08-27-2016, 01:33 AM
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Originally Posted by tothezenith View Post
The fuel map was adjusted in both instances for highest power per rpm increment. The different flow characteristics of the stacks yield different power figures from different AFRs, like in the lower rev range the leaner mix returned greater power than the right factory. Still, comparing differences to other map data i got from the multiple runs prior to this, we'd be talking differences in the 1hp range; time-vs-gain not really worth it. Could get the similar improvement between morning and arvo ride or by dropping the kids off in the porcelain bus before the ride
Modern manufacturers design and build machines which work well with the best available performance in the broadest possible range of conditions. According to their annual report, in 2013 Honda spent 66.4 billion Yen ($652 million) on research and development on the motorcycle business alone (they spent over $4 billion on R&D across all business units).

Even with extremely serious engineering, computer models and very deep pockets, engine tuning is a game of diminishing returns. You can spend a whole lot to get very little.

I'm gonna hit the highway like a battering ram
On a silver black phantom bike

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post #7 of 10 (permalink) Old 09-01-2016, 01:57 PM
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@tothezenith do you really need to remove the fuel tank to get them out? because i just looked inside and seems like i would be able to twist them out no problem just by removing the air filter, if there are no locking screws or anything of course ... either way, what i saw inside was "unlockable ponies"
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post #8 of 10 (permalink) Old 09-01-2016, 06:44 PM Thread Starter
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Originally Posted by _Yamato View Post
@tothezenith do you really need to remove the fuel tank to get them out? because i just looked inside and seems like i would be able to twist them out no problem just by removing the air filter, if there are no locking screws or anything of course ... either way, what i saw inside was "unlockable ponies"
Possibly, but I didn't try with alternative tools. You need to just loosen the three screws for the plastic bracket, the v'stacks do just twist out, but you need to loosen those screws to reduce the friction forces holding them in place. Those two screws in the top-left / top-right are the problem. You can get a screw driver on them, but being able to turn it with your hand... you'd need to dislocate your wrist!
Maybe with a 3/8 ratchet, an extension, and one of those uni-joint adaptors; I didn't think at the time to try though.

If you do go the upgrade route, it would be really great if you could be the one to do the before and after dyno runs, so we can see the difference they make with a modified 500. I do believe the Motomaxx claims are valid for the bikes with the restrictor in the stacks like yours shows, but they only have charts for basically stock engines.

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post #9 of 10 (permalink) Old 09-01-2016, 07:28 PM
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If you do go the upgrade route, it would be really great if you could be the one to do the before and after dyno runs, so we can see the difference they make with a modified 500. I do believe the Motomaxx claims are valid for the bikes with the restrictor in the stacks like yours shows, but they only have charts for basically stock engines.
yes, i most likely will do them ... but i don't have a modified engine, the only thing i have is a SC-project slipon with the baffle in ... but together with the stack i will also do the intake mod and i will compare the stock with / without modified intake and changed stacks with / without modified intake, but i have no idea when, since it's already september and the season here will most likely last one or two months tops ...
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post #10 of 10 (permalink) Old 09-01-2016, 09:25 PM Thread Starter
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ah okay, sorry for some reason I thought you have a full exhaust. interested to see results

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