Saturday, April 24, 2010

Still Trying to fix the Derbi.

So I pulled apart the derbi case and discovered that yes indeed, the engine seizure was due to a bearing on the crankshaft freezing up. Why would that happen, I wonder? I suppose it could be due to lack of lubrication, though the unburnt oil from the 50:1 should be lubing it, or it could be that this is a 31 year old bearing and at some point it's going to say NO MORE.

Since I had borrowed a bearing puller from Naz I decided to rebuild one of my puch motors while I was at it. While I was working on this I had a realization:
Almost everyone I know pulls the rubber seals off the bearings when they install them on the crank. But those seals are to protect the bearing from contamination such as bits of metal getting mixed in with the bearing when you seize your cylinder. Does it make more sense to keep the rubber on? Is there a possibility of the rubber melting within the crankcase?

Here is a picture of the E50 I rebuilt:

This motor will go very fast, it was ripping before but it wouldn't idle very well which I discovered was due to the crank bearings being totally shot.
-port-matched case
-70cc Athena Piston port kit
-19mm intake
-20mm PHBG
-3 shoe clutch

Ok, back to the derbi. As it turns out, the flat reed bearing sizes were different than a variant. Here are the bearings that I pulled out of my piston port case:
-6303 (this is the one that seized) on one side of the crank
-6302 (other side of the crankshaft)
-6203 (though this one actually just says "203", I'm assuming that it is the same as a 6203)

And in case anyone else is rebuilding a piston port variant from 1979, here are the seals:
-17.28.6 x 2
-16.24.4 x 2 for the pedal shaft

In other news I just sold old Orange and Black Maxi. That bike has been with me for a long time in various incarnations and I was a little sad to see it go. The orange and black front end was one of the first things powdercoated by Mike Rafter and the Motomatic Team and after sending everything to me he said, "I will NEVER powdercoat EBR's again." Also, this bike took second place in the Latebirds Invitational Club Relay Race. And considering first place was this bike which won the Polini Cup, that's pretty decent. But, it's departure means more money for moped parts and it went to a good home so I'm sure it will continue to rip around Seattle for many more years.

The last few moments of me and Ol' Orange and Black:

Whenever I see a picture of myself standing next to one of my mopeds I am struck with how little mopeds are. Or I am a giant. Could be both.

Gotta peel off the Mosquito Fleet badging.

That's all for now, peds are gonna roll!

Thursday, April 15, 2010

Derbis are weird.

First off, in my last post I mentioned that my piston and cylinder were pristine. Here are some photos:
As you can see, there is a little but of scoring but really it's not too bad. The rings look good and based on the performance right before the seizure(?) it seems like it's all good.

In other news, I got some new treats! First off, I'm a big fan of quality controls. Like these! These new controls are really cool. Long pull throttle, moped length tube, nice S shaped levers, and neat little levers for choke and decomp.

I also got some new reed material for my polini reed setup. Green reeds, .35mm of thickness will take me to the promise land of speed!

So I began digging elbow deep into the derbi, and I discovered some things:
Derbi swingarms are really solid.
Also, Derbi was REALLY into branding everything they manufactured.

Pop quiz: In front of you is four pullers. What do they have in common?
Answer: None of them fit into this flywheel. Looks like I'm in the market for a three jaw puller. Or at least in the market for borrowing one.
When I pulled the cylinder and head off the Derbi I discovered this HUGE spacer/ gasket. Based on the thickness of a cylinder ring I'd guess this thing is 3mm thick. I don't understand at all. Is this necessary so the piston won't hit the head? Wouldn't this raise the timing? or is the cylinder decked so the spacer is necessary for timing? I don't know.
And lastly is the pipe that Naz and I cut and rewelded. Naz did such a good job rewelding the header after we cut it that it looks like it's always been that way.

Anyhow, that's whats up in my shop. I hear that there is some scooter rally going on in Kentucky this weekend. Wish I could be there but them's the breaks.

Wednesday, April 14, 2010


Monday I was riding to the Mars Bar and cruising down 8th st in Ballard which is pretty much a slight downward incline for a couple of miles.

I was enjoying my new derbi, and just kind of blissfully riding when I thought, "You know, Phil is right, I shouldn't kit this thing. It goes plenty fast on 50cc and this way it will be more dependable." SQUELCH! The back tire locked up and I skidded for about 50 feet.

My initial thought was that I hard seized the motor... but how could that be? I pulled the plug and it looked perfect, I didn't notice any loud blats right before it seized that would indicate an exhaust leak or a massive case seal blowout...

Well, this morning I took the head off and the piston and cylinder look... spotless. Pristine. I removed the jug and have come to the preliminary conclusion that the crankcase bearings kicked the bucket. I'll post some pictures later, in the meantime, any derbi gurus know what size bearings and seals I need to get to rebuild this engine?

I read up in the Variant Manual and it looks like these are the bearing sizes:
Crankshaft - 6203/ 17.40.12 and 6204/ 20.47.14
Main Gear - 6301/ 12.37.12 and 6302/ 15.42.13

Now, the diagram in the manual shows a case inducted engine and I'll be rebuilding a piston port, but we'll see if the bearings are the same size.

Friday, April 9, 2010


Recently I bought this bike and brought it home from LA:

I was really excited to finally have a derbi to play with and this was to be my first foray into variated bikes. Lucky for me the Mosquito Fleet has some really talented and helpful people. Within a few days of me returning from the Latebirds invitational Michael Mike and I had done the following improvements:
-I had naz lathe off the restricting collar on the variator cheek
-he turned some lighter weights out of delron
-we welded a nut onto the wheel adjuster that was stripped
-we cut the header on the pipe and rotated it so that the pedals clear and the stinger kicks up at a radical angle like a simonini
-I swapped the stock 12-12 carb for a 15 SHA
-we properly spaced the front axle so that the bearings weren't just floating from side to side
-took off the crazy stock handlebars with the welded on perches and made a neat little handlebar bridge (This is one thing that drives me nuts about Derbis, the triple tree is so long that the top plate is wavy shaped and it's difficult to replace the bad stock handlebars with new nice handlebars, also, what if these forks give out? What forks have the same length head tube?)

I've been slowly going over the bike finding sketchy things and making them ultra solid so that when I'm wheelie-ing down the road with rosanna on the back I won't have to worry about whether or not the front wheel is going to fall off or if the variator is going to spin off into my leg.

Today I made some really nice aesthetic and functional improvements to the bike:
I put on some neat low rise handlebars and some new red grips, and during the process decided to simplify the wiring.

I HATE messy handlebars and the bane of my existence is ugly switches and a snarl of wires. So I had the great idea to put little switches on the riser that Michael Mike made me:

As you'll notice, there is a red switch for killing the bike and a yellow one for going into ninja mode (lights out). The caveat to ninja mode is that with the lightened variator weights when this thing is running reved (revved? rev'd?) out it is very loud. It sounds like an angry weed wacker fighting a cheetah.

Last but not least of my favorite things about this bike, the sweet ass pipe.

This was a Metrakit pipe that was right in the way of the pedals. I've always like the swept up angle that simonini's have so while Michael Mike and I were refitting this pipe to clear the pedals I positioned it in such a way that it looks really nice and aggressive. I love it. I couldn't be happier.

Further possible improvements on the way:
-New Seat. I love the stitching and the logo on this stock seat but alas it is rusted through and won't last much longer. I'm thinking about putting on either a Brooks saddle or that neat futuristic cafe seat from polini. NOT. Actually I'm thinking more along the lines of this:

-Install foot pegs so my boo can ride doubles
-Powdercoat. But what color?
-New shocks
-New Forks?
-Puch Reed kit? I have a polini four petal and a kit just sitting here. Oh the possibibilities!

Thursday, April 8, 2010

When can we stop being called hipsters?

Seriously. There are two things that squares say when they feel inadequate compared to someone younger/cooler:
1) call them a hipster
2) support their hipster claim by pointing out ironic choices the hipster in question made.

Has anyone here ever worn something explicitly to be ironic? It's such an easy game to play! "Hey look at that hipster with his ironic bob marley shirt and and his ironic bongo." That's called a hippy, friendo, not a hipster.

Am I right?!

Special thanks to die hipster for supporting my theory with every post.