Restoration Derbi GPR 50 R . France project

[toratora]

Cute photo! And the engine looks fantastic.

I am enjoying the fact that you consider a MetraKit Prorace an “easy” engine.

[RemS]

it is done!!
the Exhaust Metrakit Pro race is designed for supermotard Senda, is modified and mounted on the bike ..

changes:
removing the original bracket to create a new one for the GPR chassis. manufactured a new leakage skirt longer and welded to the exhaust body.
refurbishment of silencer (new pierced tube, welds, ceramic wool and cleaning)

the assembly on the bike is "tip-top" the fairings are installed perfectly!

next step, setting on my power bench, then GO !!!!

[toratora]

Absolutely beautiful work Remi!

I have to agree that the stinger looks a bit close to the swing arm. Maybe a spacer on the lower mount could help with that issue. Your mod to the pipe looks factory. The welds are gorgeous.

Congratulations on such a nice restoration, and thanks for sharing it with us on GPR Camp.

[RemS]

Thank you toratora

the bike is on the power bench.

Here is the verdict !!
21.86 HP at 13772 rpm and 1. 14 of couples.

I am pleasantly surprised at the result for an old cylinder of the 2000s (and yes, there has been huge evolution in the field since!)
unfortunately the engine is "hollow", but after a few carburetion tests, and tests of shims under the valve, here is the best compromise.

The bench I use is a SOFT ENGINE with the latest data acquisition system. it is the reference tool of the Italian bike preparers.

here are the pictures














the bike is equipped with a carburettor dellorto VHST under license stage6 standard model. I tested the same carburetor, but model R / T with tulipage and internal preparation. the difference in performance is not important enough for this more upscale model to be used on this simple "ballad" moped

[kaldis12]

Isnt this a metrakit pro race 70? 21hp seems way too much. 2fast 100 makes 30hp with a great setup. This doesnt seems to be a pretty decent dyno.

A bit of a spoiler my 94cc Italkit was 25.5hp on a dyno. Weirdo

[RemS]

Hi kaldis12 I'm not sure I understand your message.

Yes, this is a derbi € 2 engine equipped with a 70 cc Metrakit Pro Race (D47.6mm)

high engine Metrakit 70 prepared Balancing balance Metrakit MRD
valve box Vforce 85 CR
smile admission CR 85 honda carburetor dellorto VHST 28mm Metrakit Pro Race exhaust
ignition original derbi+ Variable CDI Top Perf Red
gearbox original
clutch mounted on bearing
disc clutch stage6 / malossi
result 21,86 hp, moreover I am more ready for 22 hp than 21 hp

[RemS]

moreover it's true a 100 2fast can give 30CV on AM6 engine, and much more on Derbi ...

an AM6 is a real shit compared to a Derbi

here is another of my machines with 100 fast AM6 (30CV without the air box)

[toratora]

Wow that's a really nice RS. I want to ask you so many questions about that bike! But I will wait until I get further along with my RS build.

As for MetraKit, when we took Ed's track GPR that has a ProRace set up it showed over 19HP on an engine that had a whole bunch of seasons on it.

[RemS]

Here are the pictures of my completed Derbi GPR.

[RemS]

Project finished !!! now next ...