DRP: Derbi Reactivation Project

[toratora]

Mihal—On that engine I have the Metrakit clutch primary shaft bearing upgrade, and MetraKit springs and discs. On most of my bikes I tend to upgrade at least the springs. But these are street bikes so I'm not beat up on the clutch the same way a drag races might. Even on my Track bike I'm relatively gentle with the clutch (which is actually mostly stock).

Thanks for the Pr0n! I really enjoy your videos.

What's with the spacer? Do they run that top end with different strokes?

Scotty—As you can imagine SF has some hills. I've never really had an issue with converting a bike to full GP Start Mode.

[toratora]

I use 48mm stroke with my Bidalot which gives 94cc (50mm bore) and that means to use the spacer with this cylinder. They do not use it with 88cc kit.

You wonder if Bidalot tried test cranks of up to 50mm stroke? That would give a bang on square ratio and give 100cc on the dot. Perhaps to go to that number leaves things a big tight?

It's interesting that the Euro engines are built so limited, where the Japanese engines NSR/TZR etc were designed with enough meat they could be made much larger with little trouble. Maybe the idea was to keep costs down, so minimise material etc?

MVT made 100cc s-race cylinder with 49mm stroke and 50,6mm bore. I have 48mm stroke and I needed to modify the crankcase pretty hard to fit it. But all of these cylinders need some port work to be perfect to get the max of it- I will test totally stock one and then modify it and test it again on dyno after the dyno will be done. Also it depends on the use of it... (different port areas,port timings etc...) I will do a lot of testing then.

I think the new Bidalot for derbi is 98cc but still 48mm stroke, different bore. Also these are small changes I do not think 98cc is better than 94cc, it is same. You have to tune it right to get usable power then you can easily beat 125cc. The art of setting it right maters.

Mihal--thanks for the reply. I thought they might do something like that when I saw the spacer.

Do you have a dyno chart of a stock GPR 50, and/or RS50? That's something I'd like to see.

My base is Yamaha TZR 50 with minarelli am6 engine. Ive never tested stock am6...

I've kind of left the Silver bike mostly stock so that I can put it on the dyno at the next dyno day. I've already put a Jolly Moto on it because the stock pipe was bent when the wind knocked the bike over. It would be nice thought to have a chart of the stock 50cc engine. lolz

I've got a lot of photos of this DRP project. Just need the time to get them posted.

Where do you get new plastics when the bikes get damaged, can you get them in the US anymore or got to look to Europe?

Tora- Looking forward to see the data then.

Scotty, the white front cowling that I got was purchased via the the UK eBay. All the nice fiberglass bits I've found out about are listed in this thread somewhere.

The non-painted bits can be found on EasyParts for very affordable prices. They also have the painted parts for most things, but those tend to be pricy.

Tora -
I feel certain that you have this laying around somewhere (so I don't feel TOO bad about asking) , but it might be helpful to some forum members if you could outline (or detail... ) the similarities / differences of various Derbi motors installed into various Aprilia bikes ... ESE vs ESB vs DB50, etc. Identification, models, whatever. Happy to help if I can.

Given my own recent Senda purchase, know it would certainly help me ...

[toratora]

The first Voca pipe I got for his bike didn't fit. I had checked in with Voca, told them what bike I had, and engine set up, which at the time was an Airsal Xtreme. They suggested getting the 90cc pipe so I did. It was gorgeous, but wouldn't fit on the bike—not even close. They had said that I might have to cut some plastic. I was okay with that, but that wasn't even an issue I could get to for the pipe hit the frame, and would exit well in front of the rear set. They told me to get a different exhaust manifold (from where?). Then they said these aren't plug and play. What? I asked if they could cut me a deal on the pipe made for the bike. At first they were open to it, but then they just stopped responding to my posts.

About eight months later I was able to get the Voca pipe made for the bike, again from Maxiscoot. I probably should have gone with a different brand due to the lame customer service action I received. But I didn't. For some reason I really wanted to try a Voca pipe.

The parts come totally unfinished. There's no clear coat on the pipe, no chrome on the mounting hardware, and it's not stainless either. Everything is nice, but not what I'd expect for the pricing. I picked up some high heat exhaust paint. It was suppose to be red, but it came out orange. lolz

Installation went okay. The pipe doesn't fit as well as I would expect, but I did get it mounted. The silencer has an orientation, but it didn't line up very well. It's about 30° off. This could have easily been made proper since it's directly related to how the mounting flange is welded onto the stinge—which is a separate piece. If it was off by a few degrees I could mark that up to a bad installation, but it off way too much for that to be the case.

The welds are gorgeous, and the pipe itself looks very nice. Unlike the 90cc pipe the logo isn't pressed into one of the cones. On this 80cc pipe an extra steel plate with the logo is welded onto the reflecting cone.

The silencer looks very nice, and the red anodized ring adds some flare, as does the graphic painted on the tail ring. It is significantly shorter than most silencers for these bikes, and as such a bit louder too. The note of the pipe is pretty nice, and the performance indicates that it will be nice once the bike is dialed in.

Over all I like the pipe. It does have some issues, and those may be enough to sway folks to get a Jolly Moto, or a MetraKit pipe. Once I get the bike tuned up and on the dyno I'll be able to compare it to a MetraKit ProRace pipe. If the Voca out performs the Metra then some of these quality issues could be over looked. The customer service stuff though, that's going to be much harder with which to be okay.

[toratora]

Tora, I feel certain that you have this laying around somewhere (so I don't feel TOO bad about asking), but it might be helpful to some forum members if you could outline (or detail... ) the similarities / differences of various Derbi motors installed into various Aprilia bikes ... ESE vs ESB vs DB50, etc. Identification, models, whatever. Happy to help if I can.

Given my own recent Senda purchase, know it would certainly help me.

There's nothing of any real importance with regards to the differences within the various Euro2 engines. The GPR engines don't employ a tapered gear so if you get a performance crank you'll have to get a gear too. The Sendas come with a tapered gear. Most performance cranks are made for the tapered gear. There should be photos of these things in this DRP thread.

The biggest difference with the Euro2 engines is that the EBE comes with a tach drive sprocket on the crank, and the other engines derive the tach signal from the HT wire. They all use the same gaskets, transmissions, clutch, water pump, oil pump, intakes, etc. as near as I've been able to figure out. The engines that come in the Senda bikes (not the engines stamped Senda) usually have a kick starter and no balancer. The engines that come in the GPR have electric start and a balancer. The GPRs came with Ducati ignitions, and the Sendas that came to the States had an incomparable Lionel ignition. So you can't mix and match the parts—but you could put the GPR Ducati ignition on a Senda as long as you replace all the parts. It would be possible to ad a kick started to a GPR engine if you swap out the clutch cover. To put a starter on an engine from a Senda you would have to machine the cases to accept the starter.

The Euro3 engine I've never had. Scotty has one and I've asked him a number of questions. With regards to the Euro2 and the Euro3 parts: the top ends are different. The transmissions are supposedly the same. The clutch might be the same. The water pump is different, the oil pump might be the same--don't know. The clutch pressure plate, and activator shaft are different. The arm on the clutch activator shaft looks to be the same. The stud spacing for the cylinder is different, and even if they were the same the Euro3 coolant goes through the block, which it doesn't on the Euro2. Near as I can tell the mounting of the two engines is the same. The later Euro3 engines got a really nice up date on the primary shaft employing a bearing on the clutch basket rather than a bushing found on the Euro2 and early Euro3 engines.

There is an engine known as the Euro1. These are probably EBE engines, and the ones that came in the Criterium and AF1 framed GPRs/early Sendas. The 80cc Criterium Euro1 engines had something around 30 HP (stock!).

[toratora]

Once I got things together I took the Black bike out for a run down to Big Basin. Previously I had two weeks previously gone down there on the Malossi bike. Very quickly I knew the bike was way too rich, but I didn't have a smaller jet and I wanted to ride. The bike was really difficult to ride. Constant hunting for that throttle position where the bike would actually move. Took out a lot of the fun. By the time I got to 236 I was quite tired, but still up for a couple of laps. I videoed the run on both bikes and I was way faster on the Malossi. Setup makes a huge difference!

[toratora]

Very sweet! Yeah they don't tell you the pipes don't plug and play for the GPR's! I have same issue, so got to cut the stinger off and then bend and make my own stinger for my pipe! A bit annoying!

Looks like nice ride on those roads if the bike would be properly set!

Must be nice to have those sorts of rides! (when jetted right)

Was thinking, how far do you ride, if you were to break down what's the get home plan? How does it work with what roads you can ride on? I'm guessing certain roads bikes under a certain capacity are not allowed? She looks good, love the little bits and pieces. Can't wait for my present to myself arrives next year. Did you spray the 125 front caliper black, or it came that way? would that be off a newer model. I found a cool brand of caliper ages ago, pretty sure it's the same bolt pattern. will have to look for them again, think they were Chinese or Taiwanese

https://www.steadygarage.com/store/adel ... ke-caliper

I go on 150 mile trips, but i trust my bike and ride it within its limits, that said i take money with me, enough to find a guy with a van and bung him 60 quid to take me home or a taxi ....never had to use it yet. But I also take puncture repair kit, basic tools etc.

[toratora]

Mihal—yeah we are pretty lucky to have some great roads around here.

Scott—I'm telling you plan on coming out for GPR Camp. Maybe I can put some plastics and street tires on the Track bike and get it plated. Then you could ride it.

That day was probably around 150ish miles, maybe a bit more. I think I had ridden more on the previous ride because the Malossi bike was running better. That day I probably did about 200 miles. Photos in The Red Power thread (soon if not already).

These bikes aren't freeway legal, but I've never had any issues with them on the freeway. I've spoken with the CHP about it and they say that if it has a moto plate on it they are going to bother you. To be freeway legal in CA a bike is suppose to have 150cc or more. Most of these bikes have more HP than a 150cc 4T so it's really not an issue. If you can keep up with the flow it's okay. If you cannot then it's an issue.

I bought a brake like that one from Stage6--which is what I think those cats copied. It didn't quite fit because the binding bolts were a couple of sizes smaller. I thought about possible solutions to make it work, but just decided to give it to one of my scooter friends and get the AJP brake Derbi fitted to the 125 2T GPRs. I am very happy with it. You can see plenty of photos of it throughout this thread. I have a silver one, and recently bought a black one to match the forks. AJP made a black version for Metrakit. I think Metrakit still fits these to their bikes so you should be able to source one from them. I think I got mine from a German eBay sale. The brake system on the Black bike is really nice. The only thing I might change is the master from a 15 to a 14. I'll probably get a 14 for one of the other GPRs and try it on the Black bike to see if I prefer it. But that's way way way down the road. lolz

The brake mount adaptor looks neat though as a possible way to put a radial setup on the older GPRs/Senda/Monza.

paperboy—We have a lot of ways of dealing with that issue. Keeping the bikes well tuned is the best, but of course things happen. If you have AAA (which I did until I became poor) they will come out and two you back from distances of 150 miles. It's about $110/year. Useful to be sure. But most of us have trucks or carriers so it's rare that we would have to use AAA. But on a moped ride in 2015 my Monza failed (totally my fault), and I had to get a tow from AAA. The guy was funny. Had to put these massive tie downs all over the bike. I'm like "dude it's a moped it's not going to go anywhere!" lolz

[toratora]

When I rebuilt the engine I put in the bike this time I used new gaskets. I probably shouldn't have done that though. It seems like these thicker gaskets don't work so well. I tried re-torquing the bolts, and that slowed the leak, but didn't stop it. Which means I pretty much need to pull the engine, split the cases, and use a better gasket set.

Since I pretty much had to pull the engine, and a few other issues I decided to pull the bike apart for the winter. ¯\_(ツ)_/¯

[toratora]

[toratora]

Dude you exhaust me with the number of times you strip that bike down! Taking a carb of the bike is tiring enough for me!

You know what's funny is this has taught me to look at parts manuals and service manuals. I may take a position that would require a freeway commute. My little bikes wouldn't be up for it. So I've been looking at bigger bikes. These bikes have taught me to do some research before getting something. I'm looking at things like insurance costs, and how hard it will be to work on the bike. You can tell a lot from a parts manual on how well a bike is designed. This will directly relate to taking care of it. Sure the pretty plastics can sway your heart, but you have to let logic influence the decision too!

The 2005 GPR is a bike that I still have a hard time believing that they actually made it. Most bikes on the market, even way more expensive bikes, don't have the features and build quality of this little Derbi. We are totally spoiled to have these bikes. It depresses me knowing that Derbi has for all intents and purposes been swept under the rug.

Seeing it all torn down makes me admire just how nice of a bike it is. The frame and swingarm look to be way more stout than on my RS50. It is sad that industry consolidation has resulted in the death (or near death) of so many storied brands. It's sad that Piaggio hasn't provided more support and allowed the different brands to seek their own identity.