mopeds


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.



Derbi SL build pt2
January 9, 2011, 12:35 pm
Filed under: Projects | Tags: , , , , , , ,

Got the beast running today. We had some little troubles with a bad head gasket then the wrong base spacing, but we got it all dialed in and it fired right up. Runs like a beast! Pretty quick, especially for a 12.12 sha. I can’t wait to get something bigger on there. We have some minor things to do still, but basically its all there. Score!

Sean got his new build fired up and its looking good. Obviously need some more little things, but hey, almost there and it sounds great.



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.