GPR Camp: Replica Racers

MT Mike's Track bike thread.

Today was a really long, and really cool day.

We started by crossing the bridge and heading down to LA.


MT Mike has been looking for a second bike for the kart tracks. His RS with the CR80 is being modded with yet a third engine, but it's taking some time. Plus, a number of us are getting set up with Derbi GPR track bikes. When folks have closely matched bikes it's just a bunch more fun when riding together.

A couple of brothers, Ed and Alex, in LA use to race a Derbi in SoCal in the early and late 2000's. We got to hear a bunch of fun stories from them. They have since moved on, and put their bike up on Craig's. I saw their post, and shared it with Mike--who decided to go for it. The drive down was quite nice. It rained a bit in LA, and then the drive back tonight was uneventful--which is a very good thing!

These photos are pretty lame, as they were basically taken in the dark. But they should give you some idea of how cool this little bike was in it's day, and how we should be able to bring it back to a significant percentage of that glory.

And so the process begins. I stared out with something easy--the silencer came in pieces, and needed a repack. Pretty easy to do. You can get the packing material from lots of places. I usually go with the $9 FMF stuff from Treats. Since it was already apart I didn't have to drill out the rivets. Nice thing too as the Arrow has a bunch of them.

So I started out with some cleaning. Then rolled the packing onto the inner perforated cylinder, finessed it into the carbon fibre tube, installed the end piece, and riveted it back together. The unit has seen come crashes so I need to make some adjustments to get it back together. It came out nice though.

I need to do this for the Metrakit silencer for my bike, but I only had enough packing material for one silencer, and since I can run the Jolly Moto can on mine for now Mike's bike won out.

One of the things missing on MTTB (MT's Track Bike) was the Woodruff key. The docs state that it's a D6888, but that seems to be a standard rather than a size. So I'm going to have to source one for it. But they seem to be relatively reasonably priced. Of course you don't really need the key because you can set it with your ocular unit.

I'll need to source the proper gasket, but here it is on the bike. Yeah a rivet didn't hold, but I'll fix it.

Back on the MTTB action today. Took apart the Mikuni TM24, and did some cleaning up. It had some yellow slim going on in there.

Well it's been a minute! If this was my bike I wouldn't have worried so much about the woodruff key, because really you don't need them. But since it's not my bike I wanted to be proper about it. I ordered one from Treats, but it must have gotten lost on the way home because it wasn't in the bag when I got home. So I went the next day to pick it up. And I had ordered the wrong one! So I pulled one off of another bike, and then went to Treats. Will hooked me up with the correct one. I should have asked him the dimensions. He did say it was like a Puch stator side, but skinnier.


I did a bit of cleaning before the final assembly--since it was a good opportunity. To set the torque I pulled the plug, and employed a piston stop. Some folks freak out about this method, but really the torque on this nut is only 35-45Nm so it's not a big deal. The plug looked good.


Then I drained the old gas. I had no idea how long it had been sitting around, so I figured it should be drained.


I also installed the carb. Then adde some fresh pre-mix. Then I turn on the MyCron, put the tranny in second, turned on the fuel, and turned on the choke. Gave the throttle o few twists, pushed, and let out the clutch. Magic! The bike started right up--even the MyCron tach was working. Of course then I had to shoot a quick video, and send that off to Mike. I found out, sadly, that feature only works with iPhones. He's got one of those super fancy Android units. Oh well. I'll have to remember the PW to my youtube account, and upload it there.

After all the excitement it was time to give it a bit of a washing.


It's cleaning up nicely.


Then it got dark and cold. I shouldn't complain though, because at least it's warm enough to wrench outside of a good part of the day.

Had a chance to pull some plastics off of Mike's bike for a bit of work. There are some cracks, and Mike want's the bike to be white.

Look like it's going to be pretty easy to sand off the blue.


Replaced the bent bar.


The exhaust manifold. This is from the Arrow pipe.


Went to bleed the brakes only to find that the master is leaking like on the Silver Bike.