Aprilia SR50R Copperhead Special

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#261324 20-Nov-2019 23:45

For those who appreciate the skill & effort involved in pushing the envelope. I bought an Aprilia SR50R with the specific intention of improving the feeble engine to decent street/race level performance.

I'm away on business so today my mechanic posted this video to show me the progress. It's nearly ready...

Spoiler alert: at 1:40 the tortured tyre gives up - popping rubber on a 50cc scooter is a rare achievement.

(Edited to add spoiler alert)

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#2358352 21-Nov-2019 06:28

We have had one at work we could use and it was full on race tuned for a 50cc scooter the thing could get up and move!

Staff member also has one kept here at work as well race tuned

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#2358623 21-Nov-2019 12:59

I took an Aprilia RS125 for a ride a few years ago, was IIRC about 30hp, some models were "detuned" to about half that.

It's fair to say I was shocked. One second you're riding a tiny little motorbike that looks like a race bike, wondering what the fuss is about as it goes like a scooter, then it hit the power band.

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#2358631 21-Nov-2019 13:08

Not yet Dyno tested but compared performance has this little beast's peak output at 22+bhp.

Small dynos are hard to find round here (rural Waikato), does anyone know of one?

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#2359119 22-Nov-2019 08:09

Just out of interest...if you were to take a normal SR50 and tune it thus, what would that do to everyday usability and reliability? Is it like racecars where you simply wouldnt do this to a daily driver?

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#2359120 22-Nov-2019 08:10

Handsomedan:

Just out of interest...if you were to take a normal SR50 and tune it thus, what would that do to everyday usability and reliability? Is it like racecars where you simply wouldnt do this to a daily driver?

reliability down the toilet

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#2359234 22-Nov-2019 10:48

The maintenance requirements are increased, as you'd expect. In particular, it'll eat spark plugs. I'm ok with that.

As for actual reliability - the rebuild has been done with top quality components from the start - mostly German Stage6 R/T & Italian Malossi brand. Budget wasn't really a consideration, achieving the holy grail of reliable performance was #1. There's very few parts left on the bike that were designed for 50cc performance - from the replacement for the 80km/hr speedo to the forged crankshaft. Engine, transmission, intake, exhaust, brakes, suspension - all replaced with either highest quality available components or custom fabricated items. Oh, tyres, replaced those too 😎.

It's not my first time at this rodeo. My daily ride is a gently-modified Peugeot Speedfight at around 14bhp - unique, economical fun. Then there's the 26bhp Yamaha Aerox - purchased as a complete project with component receipts in excess of $8k. That thing wheelstands at over 100km/hr. The Aprilia slots right in the middle.

If I have a reliability issue, I'll just ride one of the others!

@Handsomedan - This is an SR50R as opposed to a normal SR50. Huge difference between the two.

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#2359570 22-Nov-2019 22:58

looks like fun ! a lot of fun

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#2359582 23-Nov-2019 00:29

reminds me of the late 80's in Hamilton, they used to do endurance races on 50cc motorbikes, it was meant to be for street bikes but some would buy special bikes and hot them up.

The bike that won one of the races could do about 110km/h when opened up.

Looks like a lot of fun.

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#2359649 23-Nov-2019 10:23

Why do people insist on filming in portrait mode when it's most likely to be presented (as in this case) in landscape mode. I don't know about anyone else but it drives me nuts.

By the way an impressive effort with the bike.

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#2359681 23-Nov-2019 10:49

Portrait mode filming - I haven't read the thread, but surely this would be mentioned in the "small things that really annoy you" post? Gets me every time too.

I'm going to take the Aprilia for some tuning runs today. Got a stack of variator weights that basically move the power output - light weights give fast takeoff but lower vMax, heavy weights do the opposite. There's a fine balance point, often decided by .25gm.

l'll post the GPS info later. (Hoping for vMax around 125-130km/hr.)

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