PPMPR: Project Poor Man’s Pro Race

[toratora]

Well the ProRace bike runs again! Lots of power once it hits the pipe. Before that is bog city, so I need to do some tuning. I did do a quick needle drop of two slots and that help quite a bit. I couldn't do more than that though because all the jets were with the track bike. lolz

I didn't need to get much done. Put the pipe on, some coolant, adjust the clutch cable, and go for a test ride. Since I didn't have a battery installed in the bike (the Shirai that was in the bike failed) I couldn't run the MyChron to see at what RPM events were taking place. This is something that I'll want to get settled soon.

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Started in on the tuning yesterday. Made some progress, but then it started getting cold.

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The 106 seems to be pretty decent, with the needle on the second slot from the top. The previous top end ran a 114 with the same setup. I tried a range down to 98, and found 106 to be better. Still not there though. There might be a leak at the air mixture screw, and I might need to change that jetting too.

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The very first 77cc Stage6 Big Racing kits to make it to the States, and I got two of them. One for the PMPR, and one for the Silver bike (at least for now). Big thanks to Benji at Treats for making this happen.

Some of the prep work is done. It's a total rush, because I'm trying to get them ready for GPR Camp 3!! Very happy to see these are using O-rings rather than the metal head gasket like on the 88cc Big Racing kit.

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Prepping the top ends for installation.

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Details
Since its inception, Stage6 are committed to develop performance-enhancing tuning parts and don't shy away from tackling new tasks. As of now, they are getting into the market for geared mopeds by introducing the Stage6 Cylinder Kit Big Racing 77cc for Derbi Euro 2.

The cylinder kit includes:

77cc cylinder, aluminium, 50mm bore, with 5 transfer ports and 32mm bridged exhaust port
1-ring Vertex piston, d. 50mm
high compression cylinder head, monobloc, aluminium
gasket set (base and head gaskets)
The cylinder was developed in close cooperation with the MXS Racing experts; by benefitting from their considerable experience of gearshift mopeds and drawing from their own extensive technical know-how, Stage6 was able to design a thoroughly convincing new tuning cylinder.

The cylinder features a rather basic and inconspicuous exterior, but we all know that appearances can be deceptive. We're talking genuine ""Big Bore"" here – cylinder layout is not based on a modified standard model that was milled open to create a bigger bore, but was designed as a Big Bore right from the start, with matching transfer ports and a bridged exhaust port big enough to support the excess performance.

The BigRacing cylinders impress with ease of installation, outstanding performance, and high reliability.

- Installation is very easy, crankcase milling or any other modification are not necessary. Squish clearance is pre-set to a value optimized for the respective engine type.
- In terms of output, the BigRacing cylinders knock it out of the ballpark: we measured a whopping 23 PS and 13 Nm on our P4 test bench using a standard set-up (24mm carburetor, original ignition, racing exhaust etc.).
- Port timings are relatively low, cooling system volume is quite large and the piston is a top quality Vertex piston. All of these factors contribute to the cylinder's high dependability and robustness, provided that set-up and adjustments are appropriate.

Displacement is 77cc (50mm piston) and is accordingly not street-legal (in many countries). We strongly recommend a reinforced crankshaft with standard stroke.

The exterior is a replica of the original cylinder with a 49cc stamp; don't worry, this is definitely a 77cc cylinder!

Note: we recommend to use "long" cylinder head nuts to achieve correct torque when tightening the bolts.

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With the kit prepped it was time to instal it into the bike.

























Then I had to replace the bolt attaching the throttle side blinker.



Unfortunately I forgot to bring the skirts for the bike, but other than that the bike is together. With only some heat cycles on the engine I can say it runs really strong. The Stage6 BR77 promises to be a great kit.

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I was going to go out on the Friday Night Ride tonight, but couldn't quite pull it off. Still it prompted me to do a bunch of little things on this bike. First I did some quick test riding on it to make sure it would be okay to run it. The jetting feels pretty good. I noticed that the chain was a bit loose. I lifted up a bit, and the rear sprocket moved. All six bolts were loose. So I had to bend up the tabs, and torque them down. Then I did a quick chain adjustment. After that getting the panels back on.



There's a bunch of little things that I need to attend to on this bike. I have a new rear disc for it, so when I put that on I'll properly attend the rear sprocket too.

[toratora]

Finally had a chance to do some riding with the new setup. It has power, but it is really really way up there. It bogs well into the nines, and will push into the fourteens! Not at all what I was expecting from this bike. To ride it properly means to really be in the game. It does not want to be ridden slow at all. It's exciting to ride. A whole lot of fun, but not a combination that would suit someone without skills. Nor would it be fun to ride in a parade. It really doesn't like being below the nines.

The build is still very new, so maybe as it runs in things will change. I also need to tune it a little bit, but it feels a lot more like a track bike, than a proper street bike. Still I can't say that I'm disappointed with it—just not at all what I was expecting.

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Well this explains a lot! The Stage6 Big Racing BR77 factory dyno chart.

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Today wasn't the perfect day for collecting vistas, but that's okay—there were still some decent shots to find, and some new ones that I hadn't found previously.











I was finding the bike really difficult to ride today. Looks like the water pump seal blew, and let water into the clutch/gear box. The milky fluid was coming out of the gear box vent, and leaking all over the back end of the bike.

¯\_(ツ)_/¯