GPR Camp: Replica Racers

Hey Guys,

I know its not Derbi or Aprilia but the engine is AM6 from an old Aprilia so lets start this. Let's start at the beginning. (Actualy the story starts at my friend) My friend found a Rieju Mrt Pro 50cc outside of Hungary. He bought the bike for really (not really) cheap. This was when he saw the "bike". Pretty awkward right? I don't know why did he bought it, maybe because this bike is rare?





The "bike" was looking pretty bad. Where is the cylinder, Where is the radiator? What is this? BUT take a look at these pics, he did some work on it. Now this is a BIKE.



Yeah there is no engine in it, the seat is in really bad condition but wait until we come to the end. But this work is pretty amazing right now too So while the frame is "done", look at the engine. Yeah and just sprinkle the engine with a littlebit of a tuning



The gearbox was fine (We will get back to this). She got a Polini Evo stroker crankshaft (44mm Stroke). And also She got a Barikit 83cc (Im not sure in this 83cc).





Here is the cylinder (yeah its not when we installed it firstly it ran like 500km)



The piston is 50mm diameter.





For the reeds we put a Malossi vl6 in there just to be a better reed block than the stock one We also put Polini Racing clutch in there, yeah 5 clutch plates.





From this point I don't have too much pictures. At this time the bike was running with 28mm Polini Pwk carb, it ran with 34mm too. But for the better low-mid rpm we put a 28mm. I made custom exhaust with someone for her. She has Derbi Senda wheels with Mc25 Bogart Tires. Now the weels not looking the best but later on it will change.

We couldn't run it with original am6 ignition so just put up a Ktm Sx 125 inner rotor ignition with custom cdi. Yeah with that it was really a track bike. I said that we get back to the gearbox, yeah its the time. After about 400km of riding he started in 1st gear pulled the throttle and 1st gear was gone. He tought maybe the gear got grinded away or something, but no. We pulled apart 5 times the engine changed literally everything in there and no change just a grinding sound.

That was the point where I bought the bike from him. Now I bought an Italkit Selettra ignition for her. She is really happy with it. She goes with 15-45 sprockets so She doesn't stop at 50kmh

This was her story, but it just begins now. So that is that point where I will start this project thread. I have a lot of future ideas with this bike. I hope you enjoyed reading it, this was my first project thread Wonder why I need bearings? Yes because a lot of bearings got really loud and I need to change them really quickly.

Future Ideas (listing in priority):
-New AM6 engine (because of 1st gear) This will happen in August between 14-19, I will try out Skf bearings (I used Koyo) Done
-Eloxing wheels
-Plus one radiator Done
-Polini Pwk 34mm Carb. Done
-Italkit 94cc 44mm stroker kit (maybe in the winter) Done
-New custom exhaust Done
-Derbi clutch In Progress
-V-Force 3 reeds Done
-Getting temperature, rpm and kmh counters Done
-Ignitech programmable ignition Done

This is pretty much for the future. Hope you liked it I know its not really well managed project like Tora projects but maybe later I will get into it

Here is the "complete" bike.

Today I picked up a "new" engine, just to build my setup into this one. I hope I will have 1st gear.



I'm removing all the bearings and seals to fit completely new ones.



I bought some new bearings for Her. Just for the gearbox I will use C3 Steel cage koyo bearings (I couldn't find any skf bearings) I will try to get some Skf C4 Polymer cage bearings for the crankshaft because my crank bearings got loud after a short time.



Few seals for Her. And got some viton seals for the crankshaft too.



And for the last part I bought Top performance water pump kit.



Thats it for now. I'm waiting for my dremel tool to arrive, so I can mill up the cases for the cylinder. It will propably arrive at friday. I have a full day to clean the cases out completly, the outside of the cases is really bad looking so I will have some work to do. When She will be done I will polish the cases and maybe the cylinder too.

Very nice project. Wellcome to the Camp!

Thank you Rob, I need to get used to this but this wont be hard I will have a lot of future projects so keep an eye on me if anyone is interested in this

How did you mill your cases? I never ever milled am6 cases or derbi engine cases. I milled like simson (I dont know if you know this bike. In hungary everyone likes it because its good for tuning.)

I'm a littlebit nervous about how I should mill up these cases. I know there are the oil holes for the bearings. Someone told me if i mill it at a bad angle the mixture wont be able to go down to the bearing. I'm really confused right now. I had a few am6, but never milled them just for the reedblock

For the DRP cases we only had to do a little bit of work on the cases, which could be done with a rotary tool—which is what we used. For the Red Rocket I had to find a machinist in Japan to do the work. Which I did. I found Innoe Boring, and they did an amazing job. I highly recommend them if you ever need that kind of work in Japan!

For the case matching to the cylinder I use a rotary tool. With the DRP I went with an 88cc kit. This didn't require boring for the cylinder skirts. However for the 2Fast kit on the Red Rocket the cases needed to be bored for the larger skirts. This work was also done at Innoe Boring.

DRP cases


Red Rocket cases

Thank you for the information. Yeah forgot to write it out but thanks for the correction
I will try to use your pictures for a guide. What could go wrong if im milling the cases? Well everything xD last time my milling head almost landed in my arm. That would been really painful, yeah broke it

The boring is something that you really need to get correct. If you don't feel up to the task (I didn't), then I suggest that you find a machinist. It's not very expensive, as for a machinist this is a straight forward job. But for us without the proper tools, and training it's real easy to screw it up, and cases are expensive to replace (don't ask me how I know).

Thankfully I dont need to bore the cases. Just need to mach the ports. 50mm piston just can fit so its good. In the winter I will need to bore it, because Italkit 94 has 52mm piston. So for now its propably going to be enough.

I wonder whats the max skirt outer diamater what can fit in the engine? Anyone knows?

Without boring it would probably be the stock diameter of the skirts. With boring it would probably be pretty close to what the http://www.trteam.it requires.