dellorto SHA, dumb; running derbi, awesome

Just before the reno rally I spent a few days trying to get my thrown together derbi variant running. That should have been a relatively simple process figuring that the motor was running fine about a year ago in stock form. This clearly wasn’t the case. I did change a few things, primarily the top end, to a stock jug bored (long ago) to 60cc. I threw on the stock intake and carb and it ran rather well with decent pep and seemingly unlimited top speed. I went to ride it home (as I built it at Matt’s house way back in January) and it made it 1 float bowl in the stupid sha. I pedaled the rest of the way home.

So I tried cleaning the first carb, taking compressed air and carb cleaner to it twice. Same result, it died. So I tried a second 14.12 body with the same result. I asked Tom to borrow one, and this was even worse. It would kinda idle, but when reved it sounded like it was burping like there was a huge leak, but the seals were fine. So I tried cleaning that SHA again today to no avail (and why should anything change, the derbi has a spotless plastic tank).

Pissed off I finally decided to throw on Tom’s custom intake, his first from 3 or 4 years ago, 19mm funneled down to 14mm. My least favorite task on mopeds is running throttle cables, so I just pulled the throttle off ferbi which conveniently was already hooked to my dellorto phbg cap. I didn’t feel like routing the cable through the frame just yet, but I got it all bolted on and of course it fires right up and rides like a dream. It also fits in there super easy! Lesson learned: never use a SHA.

While working I also fixed the wiring which I kludged together back when I built the bike. Everything is much cleaner, the kill switch works as do the lights. So now the bike is almost done. It still needs fine tuning because all my dellorto jets are missing and my randomly picked phbg (84 main, 48 idle, needle ?) only works so well. The variator also needs some fine tuning to fully variate and reach higher RPMs. Despite it all, I think its a pretty cool bike that is fun to ride. With an air box it will keep the neighbors happy as well.

I’ve seen some stuff asking about switching derbi mags between bikes, and because all derbis have very subtle differences, the solution you come up with may be unique. This bike is older (PP) and had spoke wheels. Late bikes, or at least the Variant Sports, have brake hub tabs that are longer (they go lower towards the axle). I switched to a set of lowers from the variant sport so that the tab better held the revo hub, but the wheel couldn’t be properly centered. We then ground the hub down a bit so it all fit together. Fortunately rear wheels are easier as it seems just about all (but of course there are exceptions) have the same size tab for the hub regardless of the swingarm configuration. The biggest issue going to the revo mags is the cables as the ends on the newest variants are different. This is nothing some strong knarps cannot fix.

Finally a note if you are doing this: buy the fork lowers for whatever set of wheels you are switching to. All Derbi variants have the same fork uppers which allow all lowers to be 100% interchangeable. Tom had a spare set of revo mags and conviently forks, so he just swapped the lowers over and avoided ugly half-assed attempts at removing forks and grinding hubs.


’tis the season

hello fellow readers, sorry for the lack of updates the past few weeks. Well I am back from Hawaii (1st trip there, so much fun!), and that moped rally in reno is happening this weekend. There should be 6 of us superteens there, so get ready for some crazy fun times.

yesterday we had a little fix-it bbq at my house, and in typical fashion we didn’t get all that much done. Well that’s a lie, Bret got his maxi running after some silly wiring snafu, and Tom got his sweet new variant sport going but it is really really loud and I don’t think my neighbors were all that excited about it.

My green derbi is still being a turd, and after 2 different carburetors and some cleaning I think its time for a 3rd. Hopefully I can get one from Tom tonight, then I can throw that on with the sweet ninja pipe I am borrowing, then it should be able to rip for prolonged periods. When it was running (for exactly 1 float bowl before dying), it was fast. The bored out cylinder, ninja and clutch springs (+TJT) along with a 20t front and super small 32t rear make this bike quick off the line with a predicted top speed over 45 (maybe more downhills!). So yea, I’m excited but not in that its not running now. If I can’t get it dialed I’ll just bring my boring old magnum

Sean is building what may qualify as the ugliest maxi ever. He got an old newport frame out of Matt’s yard (rusty, faded, ugly), is reusing his grungy 5-stars with custom (crusty) white-walled vm100s, some faded old red freespirit forks, some rad bicycle bars, and some random pug shocks. Power wise its solid, with his old athena kit, 21 phbg (he was gonna build an intake, but why do more work when you can just trade parts with Tom?), and a really really chromed out biturbo. All in all practical, ugly, and probably structurally questionable.

Sorry, no photos were taken because we were working super hard, or maybe we were just drinking beer. I’m not sure, but the sausages sure were tasty. See ya’ll in reno.

Derbi SL Build Part 1

Matt and I started getting the SL all put together. We started with this:

Plans are to use the Rev mags, his green frame, my c-5 piston port motor with a bored stock cylinder, tjt, some pipe, treats cdi, dellorto sha, etc.

Of course in building any bike nothing is as ever as easy as it should be. For example, we had to mess with the forks because of course (as its a derbi) the brake hub tab on there differ for every year of production. Older bikes have smaller tabs higher up. These barely work with the rev hubs, and we determined it unsafe. Fortunately Matt has a set of never Variant Sport forks which have tabs that run much lower (to down closer to the axle), so we decided to use those.

If you’ve ever messed with derbi forks this picture should ring true. Gosh what a mess, and how it is NEVER easy to get those little rods in the hole (that’s what she said?). After much fandangeling, I got them in but turns out the wheel spacing is still wrong. So we sawzalled the tab in half on the fork arm to shimmy the wheel over, but even still its way off. So now we have to mod the hub plate to get that wheel centered so we can run a fender.

So its almost done and looking pretty cool. The big pirellis have about the same profile as a regular 2.25×17, so the little wheels don’t look too stupid (meaning big ‘ol fender gaps). We have to figure out the exhaust situation, find a carb, hook up the ignition, and get the front fender shored up. Exciting times. Oh yea, gotta find brake cables that work too.

derbi variant sport
July 15, 2009, 1:42 am
Filed under: Uncategorized | Tags: , , ,

so it was a sport, now its a mutt with parts from multiple derbis. DS50 motor, sport frame, variant sl forks, fenders and wheels. Ugly yes, one day pretty? Maybe.

This cylinder is awesome. Beautiful port map with all these boosters. It revs up really nice and sounds awesome.

limited rebuild
July 2, 2009, 4:53 am
Filed under: Projects | Tags: , , , , , , ,

So back in LA I noticed the rear wheel of my magnum had a little bit of play in it. I proceeded to blast a lot of people and hit personal land speed records. The other day as I rolled the limited on the stand I noticed the rear wheel now had about an inch of play (at the tire) and I dunno, I guess thats bad. So I pull the wheel apart and find some nice bearings. One is all crusty, the other looks almost decent, but 1 or 2 balls are dislodged from the cage and they move around way too much. I don’t want that blowing up at 55, so new bearings are in route.

The motor is getting closer, and now I have a lot of CDI boxes to try. I’ve got the OG hero box that I used for a few months that ripped, but benji thinks these others may in fact be a little better, so we’ll see. I’ve got these 3 to test and the other box is currently living on derbi if I need it.

I got a place to live, so now its time to finish the mopeds. I’m going to bring derbi (i think i decided on variant sport frame over ds50), and I need to finish the white magnum and sell it, just a few cosmetic touches there, and I want to get the limited running just as well as it did before, and I’d like to station that in the city for moped rides, and I need to get my racer tidied up for the september (maybe july???) races. So yea, I’ve got a lot to do. All must rip. Oh yea, fixed my friend’s derbi, turned out a ground was disconnected. Super nOOb