Derbi—The Red Power

[toratora]

One of the cool things about living in San Francisco is that I can go visit the Stadium where they shot Dirty Harry. Now the one in the movie was torn down sometime ago, and they built up a now one. Still it's the same place.

[toratora]

Good stuff. I've seen a port mapping tutorial once before but it's always good to have it explained again with good quality pictures to go with it. That looked like a nice ride. Man, NorCal has such good riding weather. The picnic site in the forest looks so peaceful.

That looks like a beautiful place to live and ride. Of all your GPRs, do you have a favorite?

Hey Free, yeah this is a pretty cool place to live (most of the time). The photo of the campsite is right next to where we'll be staying for GPR Camp this year. I just posted a video of one of the roads we'll be riding too. I made a version of it with music, but you can't watch it in the States.

https://www.youtube.com/watch?v=za7eabZJdfk

ESP, well there are three. There is my Red bike which was my first GPR, and I've had a lot of fun on that bike. And that's why I put a bunch of effort into the custom restoration.

Probably my favorite of all time though is the Black bike. This a photo of it after I was hit by the Honda Driver. I wasn't able to get it running properly after the crash, but I hope to have it back on the road this year. That's why I built up a second engine for it.

And there's right now. The Silver bike I picked up recently to have something to ride. I'm having a total blast on it. It's weird riding what's basically a stock fifty after riding the hopped up bikes, but it's still fun.

That's really cool to hear. I was so surprised by the drive-ability of my Aprilia SR50R (post mods) that I didn't go with a big bore! I would like to find a bone stock benelli framed bike to fawn over someday too!

My 2005 came with 1.5HP, running a plugged exhaust, and a 14mm carb. It was not fun to ride--felt like someone had grabbed it by the throat, and squeezed the life out of it. But when it received the 1266% increase to ~19HP it was heady to ride. ;P

I'm really looking forward to what it will do when I get to exercise my new skillz of engine building/tuning on the next iteration of the bike. Hopefully next week I can join you with the waiting of the big parts order.

Oh and I think I saw a Nude for sale in Canada. Might be tricky to bring it to the States, but maybe not.

[toratora]

Celebrating ∏-day in San Francisco.

[toratora]

I'm currently wrenching on four bikes at the same time in an effort to get them ready for this summer's events! It's a bit heady to keep them all moving forward. This bike is getting very close. I noticed that the brake fluid resovour had never been opened. That's around thirteen years of the same brake fluid. It's been very windy around here so I had to wait it out—don't want dirt flying into the system. Yesterday though was pretty nice, and provided opportunity for changing out the fluid. Front and rear brakes now feel much much better.

While ordering parts for the Black bike I noticed that EZ Parts had this manifold for around 7€. I figured it was worth a try. It fits the carb well, but is clearly made for smaller carbs. I've taken the rotory tool to it and will have those photos later.

[toratora]

@ToraTora This is my first post on this forum and I want to start by saying a huge thank you to your for this thread. Your in-depth coverage of your GPR 50 escapades is just brilliant.

I am based in Kobe, Japan and I am looking at buying a GPR 50 2000 model. I currently own a Honda NS50F.

I noticed that you've added the arrow after market pipe on your silver GPR, what effect (if at all) does that have on performance? I'm assuming it's fairly minimal right?

What other mods would your recommend to boost performance without going the big bore route?

I appreciate your time and input.

Best wishes,

Will.

Thanks for the nice words Will. Glad you saw the PM too.

I've been super busying with GPR Camp planing, and getting the bikes ready. So much to do! That bike you are looking it looks very sweet. The cat seems to have taken great care of it, and while the price might see on the higher end the bike is probably worth it. I've seen ratty bikes priced in that neighborhood.

[toratora]

I've been working on another bike to have ready for GPR Camp. It came with an Artech pipe. I swapped out the stock carb for the Del 21 Racing that I have, and I could not get the bike to run properly. I thought it was a clogged pipe, or silencer. Inspected them and they were fine. I went through a whole number of things, and I was stumped. I finally decided to just put a stock pipe on it to see what it would do. That's when I discovered the real problem. Removed that sucker and now the bike runs like a Banshee.

[toratora]

Once the restriction hurdle was overcome I've been able to make some decent progress on this bike. It's running an EBE075 with a Del 21, and the Artek pipe. Stock reeds, and with the stock air box. The main jet is a 92. With the 075 engine running the Del 21 a 92 seems to be somewhat magical. But we'll see how it goes once the bike is all set for some proper test riding. This little bike has been sitting for probably six years or so, and it wasn't really put together well back then either, so I've had to go at a lot of little things to get this bike sorted.

[toratora]

The previous owner of this bike didn't like the full farings and had fitted a motard head lamp to the bike. That got disappeared on the freeway. Plus I'm installing a complete set of farings on this bike. One of the issues was returning the wiring system to support the stock headlights.

I kind of went a bit overboard, but I really don't trust crimping with the tools I have. So I tend to solder, and then add some heat shrink tubing. Makes it very nice.

[toratora]

Ed and I have done a serious amount of forking around with these bikes. This bike came with the newer forks, but currently has an older set. For these we can employ the AllBalls seals. The interesting thing about these forks is that there is a nylon insert that occludes the hole in the top of the shaft. We ended up drilling a couple of holes into the nylon part in order to gain access to the hole for proper torquing of the upper bolt. The service manual could do with some better instructions for the forks rather then remove the bolt, and torque the bolt!

The forks feel much better now, and they don't leak.

I was also able to get the intake manifold finished up, and mounted. I did have to change the main jet from a 92 to a 90 with the manifold change. I'm not sure why that would be. The new manifold does have a built in stuffer, and that seems to make enough of a difference that the 92 was too rich. This manifold created a shorter path from the carb. The throttle response is notably quicker.

[toratora]

Solder n' heat shrink is the ONLY WAY to go. Those tiny pin connectors are an enormous PITA - Very nice!! That's an interesting manifold, with the integrated stuffer, too !

I do feel like I'm over doing it, but I really don't trust the crimping tools I have.

The manifold is a bit of an experiment. So far it's working out well. Should have the bike out on the road soon. Might even take it out for Derbi de Mayo.