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2016 Aprilia RX 50

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Jaxx
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2016 Aprilia RX 50

Post by Jaxx » Mon Jan 20, 2020 10:21 am

I've decided to create (I've should done that while ago) project thread about my bike, it's much more convenient then opening new thread for every question etc..

Anyway, bike is 2016 Aprilia RX 50 (Derbi Senda DRD R/Xtreme with Aprilia stickers) that I bought two years ago, it is EURO3 version with D50B0 engine:
Image

Bike has standard Kayaba front suspension forks and linear rear shock (there is 'Factory' version of RX 50 with USD forks and progressive rear shock from 2018 on) but they are 41mm, which is massive for this size of bike :flushed:
Last edited by Jaxx on Tue Jan 21, 2020 10:48 am, edited 3 times in total.
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Re: 2016 Aprilia RX 50

Post by Jaxx » Mon Jan 20, 2020 10:59 am

Bike is stock except pipe is Turbo Kit Bufanda R with carbon silencer stock carb (PHVA 17.5) is up-jetted and end gearing is changed to from 11/53 to 13/53. For this year I'm planing to do a few things:

- change stock CDI to Malossi K15 with rpm limiter
- change stock cylinder to Stage 6 Streetrace 77cc, 50mm bore. I'm currently not planning to change carb, I hope that PHVA 17.5 is big enough to rev it to 9500 rpm...?
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kaldis12
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Re: 2016 Aprilia RX 50

Post by kaldis12 » Mon Jan 20, 2020 9:57 pm

The biggest problem with a 17.5mm carb on the 77 is that the entire "average" powerband will get lower but the "cylinder's band" wont. I think the top rpm is around 12.5-13k. You will get a noticebly weaker performance from that kit. I would recommend a 21 or a 24mm dellorto phbh carb, or something like this.

((I would change the exhaust too, but thats kinda up to you, whats your preferation))

In ome sentence, if you want to get a nice power out from that cylinder then go with a bit bigger carb.(but under 28mm)
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Jaxx
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Re: 2016 Aprilia RX 50

Post by Jaxx » Tue Jan 21, 2020 11:11 am

I'm aware of this. I don't want to get most HP of this cylinder, I just want more torque below 8000 rpm. The only reason I want bbk is that 50cc has to be constantly pushed over 10.000rpm, and that brings noise and I don't want to bring attention, if you know what I mean:secret:.

I've made a quick port map of Stage 6 Streetrace 77cc:
Image

About pipe: this one is identical to Radical Racing Sport, Hebo Performer, etc.. Gearparts24 tested few pipes on 70cc Airsal Sport and and this one was a winner, it's starts earlier then Tecnigas and Leo Vince for example and peaks higher...
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kaldis12
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2016 Aprilia RX 50

Post by kaldis12 » Tue Jan 21, 2020 10:20 pm

That is a nice map for a low-end working cylinder 182/125 degrees. Pretty cool. Would still run a 21mm carb still though!
It will make pretry decent power with 21mm and wont bring the powerband up that much.
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Jaxx
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Re: 2016 Aprilia RX 50

Post by Jaxx » Wed Jan 22, 2020 11:28 pm

Image


Malossi 12*15*15 small end bearing and Stage 6 50mm piston:
Image


There is approx. 1mm of free play axially on each side.. That's stock bearing dimension, maybe I should get one with 17.5mm width...
Image
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kaldis12
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Re: 2016 Aprilia RX 50

Post by kaldis12 » Thu Jan 23, 2020 4:20 am

Make sure that the needle bearing is not tightly fitted in there. Also if the needle bearing is wider than the conrods width then you get a bit better lubrication.
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Re: 2016 Aprilia RX 50

Post by Jaxx » Sat Mar 28, 2020 1:07 am

I've read about Tora's problems with Stage6 kits (cylinder-head leaks...) I notice that most kits have O-ring seal seated in cylinder, but Stage6 have O-ring in the head. Could that be the reason (some sort of design flaw)? As I can see Streetrace 77cc has identical head as BR 77cc...
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kaldis12
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Re: 2016 Aprilia RX 50

Post by kaldis12 » Sat Mar 28, 2020 10:07 am

As far as I can remember that was a design and manufacturing flaw. If I remember correctly they fixed that issue a good few months ago.
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Re: 2016 Aprilia RX 50

Post by Jaxx » Sat Mar 28, 2020 10:43 am

So much about (over)hyped Stage6... I remember few years ago, when you could just sell stickers with Stage6 logo and make good business, kids with scooters would grab them all :laughing:
I've read that Stage6 went in finacial problems recently and that their newer kits are casted in China by same company as Airsal does.
If I look back I would take Airsal 80cc Sport and pay 50 euros less... :raised:
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