GPR Camp: Replica Racers

Yeah it can be hard to describe the Derbis due to getting released at different times in the States and Europe, plus some folks go by when the bike was first registered.

If you look at this photo the bike on the left has the 2002 livery, and the bike on the right has the 2003/4 livery. Both bikes though are 2003/4. I just fitting the 02 livery on the one on the left. Also note that the faux tank on the left bike is actually from a 2003/4, and forks are from a 2000. :p: Because your frame is silver, and the forks are gold Sebacs it's clearly a 2002 model year. All of the bikes with the vertical lamps are considered Second Edition (of the Cagiva framed GPRs). The SEs also had many little changes to them. Some of these changes make swapping the farings around a little challenging. Many of these changes were obviously cost cutting measures. But one of the nicest changes they made was the tach was no longer controlled via cable. I believe this to be the major difference between the EBE and the EBS engines.

The bike on the left is the Ui/Lorenzo livery, and the bike on the right is the Marquez livery. Ui also had a lot of replicas in the first edition plastics. And only the Ui bikes with 16" wheels came with red wheels. If you see three spoke 17" wheels those are not from the factory. The red wheels on the Silver bike were black. I had them powder coated red for the Red bike (which is not in this photo). The Red bike's vision was to look a lot like Ui's all red livery with the white Derbi logos—which is why the SE farings were chosen. Hopefully when I re-build it I'll be able to accomplish that goal.

I've pretty much switched all my bikes over to pre-mix. This has a way of tweaking your brain. As you can see from the photo above something bad happened. The really sad thing is I was even carrying a bottle of oil with me!


What's even sadder is that you can see from the wash this bike was tuned really nice.


Thankfully I have another engine from my first GPR that I can run until I find a replacement top end.


So it was time to get to work.


Another thing I found is that going down those steps at the Moped rally did some damage to the Arrow pipe. I'm going to have to try some of those repair techniques I've seen on YouTube. lolz


I did some cleaning on the engine before putting it in the bike.


Some long shots.

One of the tricks to pulling this engines is to loosen up the swing arm spindle so that the rear mount can swing out of the way. The thing is you need two thin walled 22mm sockets.


The lower radiator support needed some attending, and since I was doing some painting I figured I'd match up the rear sets since one of them was black, and the other was silver. lolz I cleaned them off real well with acetone, but apparently I didn't let them dry long enough. Eventually though it smoothed well enough.


The rear sets are pretty easy to get at on these bikes, but the brake side is a little bit more involved.

I figured while I was in there it was time to do some upgrading, and finally put some Malissi parts on the Malossi bike.


Another important task when doing this sort of thing is a leak down test. This starts by getting the exhaust manifold on properly.


And as you would expect there was leakage—I had never seen it at the plug before! And I would end up needing an exhaust gasket this time as the sealant wasn't enough.


More long shots!


Because I didn't know how old the trans oil was I had to flush it. The Derbi engine has two drain plugs. One under the engine, and one on the clutch cover. They are shared, but there is a wall between them that keeps most of the oil separate so that practicals don't get mixed up.


A few more things with water, the exhaust, and what not.

Another issue I had to deal with was priming the oil pump—I was pretty certain that it had run dry! It took a while to pull this off with a drill, but eventually it worked.


A couple more things. One of the things that would have saved the top end would have been the idiot light—because the idiot (me) riding the bike didn't keep enough oil in the tank. Well I didn't have the clocks on the bike yet because well maybe I have too many bikes! So I made sure to put the clocks on the bike. The main reason I hadn't put them on is I didn't have the silent blocks for them. I had tried to order them from EasyParts but they were no longer available. Actually you can get them, but you have to order them from another bike. To deal with it I tried JB Weld. This seemed to work, but one side failed.


The smallest jet I had for this carb was an 85. This was still too rich for the bike with the airbox and Arrow pipe. I now have some smaller jets (big thanks to Richard!!!). When it warms up I'll do some tuning. In this cold it would be pointless to try tuning the bike, and being a little rich right now is probably a good thing with all that dense cold air.

A funny note I'll share here. On the Silver bike on Saturday it was so cold that the peak HP jumped about about 1500 RPM! I had never had that happen before on any of my strokers. It really surprised me.


The Malossi bikes is mostly back together, and I'm really looking forward to riding it again.

mihal wrote:Nice swap! Hate when I find leaks and have to do it all over again.

I'm actually happy to find them because that means I wont be blowing up an engine due to an air leak! lolz This is a technique that I recently acquired thanks to Matt. I now make sure to get out the bubbles, and check for air leaks when doing these sort of changes on the bikes. I was very surprised to see how often they show up—even if you do things properly they still show up. Testing is the only way to makes sure that you wont be plagued by an air leak.

mihal wrote:I know! I do leakdown test everytime the engine is assembled. I just meant that I like to pass it for the first time.

Have you pulled that off before?

We have this event in SF called the Dirt Bag Challenge. They build choppers with a $1,000 budget, and one month. It's kind of goofy, but the turn out of moto people is pretty cool. This year I found some Debris with which I could park. Of course they were friends of mine.

mihal wrote:I assembled a lot of engines even veterans and from time to time I am able to pass it for the first time I use pressure of 6-9 psi. Sometimes its quite a pain to get everything done properly... Is that challenge docummented somewhere?

Since I've started testing them I don't think I've been so lucky. Well maybe with MT Mike's engine, but I think that one had some bubbles too. I was actually surprised how often there are bubbles, but that explains a lot.

I think it has less to do with the builde—well at a certain level anyway. I suppose that if you were to slop tons of sealer on everything it might ensure no leaks, but then that recent leak at the plug, and the exhaust on the Malossi bike were somewhat unexpected.

scottydog wrote:one thing I do after each engine build is to put the whole engine in the oven to bake and then when it cools retighten the assembly bolts.

mihal wrote:I do same thing but I just bring the operating temperature by starting the engine up and then checking it again. It is important with studs because there are fluctuations in forces when it is heated and cooled. Thats why people should not tighten the studs or any bolts too much because they will overcome the elastic point of the material and by "relaxation" it will stay in plastic deformation which means it will be loose. After time usually elastic tension also become plastic deformation so bolts should be checked even after good running in.

Yeah I do it the same way as Mihal. But the oven idea is interesting. Scotty what temp do you set it to when employing the oven?

varesecrazy wrote:great pics,
thanks for sharing

Debris - are we blaming the spellchecker.

never seen a C-4 before, great looks - like my Garelli / Fantic youth..,

Charlie

I type hella fast. Usually way ahead of the auto typer. It will go in and mess with my typing long after I've typed it. Most of the time I fix it, but it does happen that I don't catch it. This does irk me and I have been known to go back in and fix the spelling. Frequently it will get forms of speech incorrect. Things like adding an s to a word to make it plural, for instance.

That particular C-4 doesn't actually have a Derbi engine in it!

Rj_666 wrote:That makes me happy.

almost looks like a Tomos

I've been looking into the new Stage6 Big Racing top ends, and they are looking fantastic. The cats that worked on the MSX worked on the design of the new Stag6 top ends. They did some pretty amazing work too. Look at the evidence.

These have become so hot that Maxiscoot is completely out of stock. But it just goes to show that getting the ports properly designed can make a huge difference. This the same thing that Derbi did to ring the RSA to prominence. The folks at MXS studied the RSA engine, and put their learning to practice with the MXS top end. They were brought in to work on these two Stage6 top ends, and from what I've been seeing these are pretty amazing. :lover:

These are available for Euro2, Euro3, and AM6.