Derbi GPR Track Bike

[toratora]

I kind of knew what I wanted, but since I don't have access to a workshop these days I pretty much had to wing it. It came out about what I wanted, and I'm mostly happy with it. The bends could have been better, but considering I don't have anything close to the proper tools they came out great. I figured some folks might want to know how to make these so I took a lot of photos to help understand the process of how to fabricate something (on the fly).

I had a big chunk of aluminum sheet scrap with which to work. Holding it up to the bike I could get an idea of what I wanted.

First I drilled a proper size hole in it as a reference. You have to start somewhere.

With the hole in place I employed some green painters tape for a cut line, and then cut it with a jig saw. It wasn't as straight as I would have liked, but I'd be able to clean it up with the file.

Checking out the fitting, and measured for the next hole.

With the second hole in place it was time to mark the top cut. I would have to cut this left handed because it's really difficult to get a good cut started on such an angle. Then I added a nice radius to the corners with the file.

With it in place I could figure out where the first bend would go. I decided to make the bends parallel to the frame of the bike.

To achieve the bends I used a chisel to mark the crease. Then used a couple of wood blocks, and some hand force to make a bend.

Same thing for the second bend.

The bottom needed a bit of trimming, and a bit of radius to the corners. After which a quick sighting for the final hole marked with a Sharpe.

Then clean things up with the file, and put it all together.

[toratora]

It's nice to be able to get some good wrenching in on this one. A couple of days ago I got the petcock switched out. This one is much nicer. I only have half of the new tubing I needed for it, but that's better than none.

One of the things I really needed to attend to was swapping out the silencer. I had the really nice JollyMoto on the bike and it would totally suck to mess it up with a low slide.

To replace it I had this beat up MetraKit silencer that would do just dandy, but it's much heavier than the Jolly (which is why the Jolly was still on the bike).

This meant that my temp fabrication binding strap solution would no longer be acceptable, and therefore had to go. I had always planed on doing this work, just never had the time to get to it.

Had to clean up the pipe and silencer a bit, and the copper coat them.

Replacement of the lower support unit.

Connecting the silencer.

I also did a bit of work on the rear brake lever since it had gotten loose again. Got it all adjusted and cleaned up.

Next it was time to get to the fabrication. This is super heavy with photos so I'm doing to do it in another post.

[toratora]

Yesterday I was working on the chain when I noticed that the bottom roller was missing.

Digging through the boxes today I found some roller parts.

After cleaning things up, using some new stainless washers and nylock nut things started looking the way they should.

With the chain replaced--I did this yesterday. The chain on the bike showed way too much stretch, and I had this chain from the Black bike that was in good shape, but a bit dirty. So I cleaned it up, and fitted it to the track bike. I also dropped the front sprocket down one tooth. I would have probably had gone down another but I didn't have a 13 hanging around. But to go to a 13 would require getting a different chain, or pulling some links.

Another thing I'm looking into is a way to protect the frame if the bike goes down. This super ugly tail section is hanging around so I might clean it up and employ it.

[toratora]

Technically evolution happens within a population, and not on an individual. So it's not the correct word in this case, and what I really mean is gradual refinement. I finally got the new brake reservoirs fitted to the track bike. I still need to work on the mount for the front, and I'd really like to replace the hose for both of them, but this will do for now.

These are the units I ordered from China on eBay. They are nice enough, but they do come all scratched up because the put the hardware in the same bag an the reservoirs. It's a shame because you can't order these for any project that you want to look nice. In this case I suppose it's okay because a track bike is one where you expect to crash.

I'm replacing the stock rear, and the nice Procircuit unit from the Red bike that's been on the Track bike for a while now.

And the new Chinese brand units installed.

While doing this swap I noticed that the front brake felt a bit soft. So I did a quick bleed job on it. Now I'm thinking that the Brembo I have fitted on this bike is way too much master. It's the 16x18 track master. It's very nice, but on this bike with it properly bled it feels rock hard. Very little modulation. I'm going to have to source a different master for this bike too.

[toratora]

The leads from the kill switch on the Track bike were of a different type than what was available on the bike. The lead to the CDI unit happened to be the same which was nice, but the lead to ground needed a proper connecter to the bike. Today I had a moment to fashion up a short adaptor wire. Sadly I've run out of appropriate heat shrink tube and had to improvise with the old fashion method of electrician's tape.

[toratora]

We went up to Sonoma for some circuit riding. The White bike it MT Mike's, and the Black bike is mine.

[toratora]

The Reese Jupiter shock fitted to this bike (thanks to Owen!) has a remote res. I needed to come up with a better mounting system for it. I took some inspiration from the silencer mount that I had previously made for the bike.

[toratora]

Found a really old photo of the Track bike before it was the Track bike.

I think every single part on it has been swapped out.

[toratora]

A little discovery:

New project bike? I'm sure if anyone can bring that back to life it would be you!

I'm collecting bits for the next GPR Camp build fest. Picked up another one on Sunday. So much work to do! lolz

[toratora]

Just got this link from Scotty Dog! Oh my is this cool. Now the newer versions of the Euro3 come with this built in, but the early ones don't have it, and the Euro 2s never had it either. MetraKit did make something like this, and I have one installed on the 45mm stroke engine. This is a really nice upgrade!

https://www.scootfast.net/pignon-cloche ... derbi.html

Google translation:

In 50cc with box the Derbi engines are reputed to be the best performers. However, they still have a weakness in the transmission when one starts to have a motor a little more advanced. In fact, the clutch bell pinion undergoes high pressures and the friction with the ring creates a deformation of the latter. As a result the bell remains blocked with the box shaft. This type of mounting on a needle cage thus prevents friction and therefore wear on the ring. Derbi has been aware of this problem and since 2014 they also use this type of assembly in original equipment. The Racing clutch bell gear has needle cages of 20x26x12 for high resistance.

cheers Tora! Was a lucky find as I have been on that site many times and not noticed it. I got lucky recently to have found old stock with the Metrakit version, but it's totally awesome to have this available and makes me comfortable as a Euro 2 fan!