My 2002 Derbi GP1 Scooter Project

Modern Scoots from Vespa, Lambretta, Piaggio, Aprilia and Derbi
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My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

I bought this Derbi Gp1 that had a blown engine, I drove up to Seattle to pick it up. I've always wanted one but they rarely come up for sale, but it's kind of a gamble since it needs work. It's the first non Honda scooter I've owned and my first water cooled engine also. The previous owner claimed it did 55mph with a 70cc BBK before it popped. I've all ready got a new top end on order, hope that's all I need to get it running.
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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

I noticed some shards of metal in the case from the blown top end. I decided to flush it with brake cleaner and premix then suck it out, repeated that a dozen times.

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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

The exact reason why it blew is unknown, looking at the old piston I'm guessing it was running lean and got too hot. This derbi also has a aftermarket exhaust pipe and little bigger carb. I'm thinking the previous owner took off the stock airbox and installed a high flow filter without re jetting. I'm avoiding splitting the cases, if I had to this project would probably go on the back burner until winter.

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Re: My 2002 Derbi GP1 Scooter Project

Post by tiny »

That piston looks like utter crap. Wow
That thing should easily hit 60MPH in 70cc form. 55MPH in 50cc form should be a given. My wife's '03 Vino will hit 88kph and it's still a 50cc 2stroke.
Good luck on the rebuild.
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Re: My 2002 Derbi GP1 Scooter Project

Post by GVH »

Need a favor. can you take a close up pic of the coil/cdi unit. need to figure out what plugs in to it.

Thanks
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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

GVH wrote:Need a favor. can you take a close up pic of the coil/cdi unit. need to figure out what plugs in to it.

Thanks
I don't think you can see much of the wiring right now. I looked at the last pic you posted on your thread and your wiring might be a bit different from mine.

Have you found the PDF predator manual online yet? I can send it to you it through email.
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Re: My 2002 Derbi GP1 Scooter Project

Post by GVH »

tyler vr wrote:
GVH wrote:Need a favor. can you take a close up pic of the coil/cdi unit. need to figure out what plugs in to it.

Thanks
I don't think you can see much of the wiring right now. I looked at the last pic you posted on your thread and your wiring might be a bit different from mine.

Have you found the PDF predator manual online yet? I can send it to you it through email.
Found a general pdf of all Derbi Piaggio units
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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

Got the new top end kit, it's a cheap one off ebay. I think the old top end is a brand called airsal, it's a aluminum jug and the new one is cast iron.

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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

I went to install the new top and was torquing the head bolts when a head stud snapped. I was lucky enough to get a easy out to bite and got the remaining threads extracted from the engine block. I'm going to try again tomorrow with just some m6 all thread.

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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

It runs, just doing some heat cycles to break it in.

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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

I keep blowing fuses just seconds after the ignition is turned on. The engine still runs, but I haven't rode it yet, so I've just been heat cycling it. I figured out the problem was the voltage rectifier/regulator; blew a lot of fuses trying to figure it out.

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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

Got it together, rides pretty good.

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Re: My 2002 Derbi GP1 Scooter Project

Post by GVH »

Sweet. Nice work on fixing it. Now could you fix mine please.
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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

Well the ebay kit popped a head gasket, just under 100 miles. I was heading to work when it overheated, it was running when I turned it off but wouldn't restart. When loading it up in a truck I saw coolant dripping from the exhaust pipe.

I all ready pulled the head off, the head gasket o ring just doesn't fit in the groove good enough. I could probably get it running again if I get the correct thickness o ring to fit in the groove. But my plan is just to buy a malossi 70cc top end kit.
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Re: My 2002 Derbi GP1 Scooter Project

Post by tyler vr »

Got the malossi top end kit, its a lot higher quality than the ebay kit.

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