Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/141037
Ol M " m '" 0.. N .... Ol Ul ~ If /.00 0 ~ w Z W ..J U >- U Engin e. We ll, actu ally th ere is more yo u can do to w ring th e last ounce of powe r and performance ou t of th e pin t-size powerho use. C all it STAGE II I -A a nd prepa re for a permanent reed valve se t-u p on yo ur Rickman Zun dapp. An addi tional transfer port can be cut at a 30 degree pl a n e f ro m the vertical d ire c t ly in to the re ed c avity . See w hat it lo o k s like in Fig . 6 . You r engine stays this way unless you la te r p lug up the hole, a tedious process. It's an additio nal boost port taking a smooth flow of fu el ch arge in t o the cy lin d er and, lik e the name says, it boosts . This, plus th e other Stage II I mods is a total BTTW ra cing p ack age. You will have o n e very fast Rickman . There ' s n o apparent end to h ow fa r you can go to produ ce the ul timate lightweight ra cer give n time and bread, particularl y the large sac k s of go ld . Kn owing what y o u ' re doin g h elps, o f c o urse . I f BSA ever fields a full up , factory backed, n o h o lds b arred Rickma n m o to cro ss team , th e bik e th at E .C. built for Billy Barnes will p rob ably be used as a modcl. T ak e a stock Rickman Zundapp and add ab o u t $ 1700 over a nine mon th ge st atio n pe riod and the res ult is the machine yo u S('C on these pages , decked out in pai nt by Molly . c:==::::::::::::;;~-T----~\---~T--~~~~~~~~~= T he 10 0cc machine is piston po rt ed and is very competitive in class . ~---- If you're interested in what's possible, the following items are some of th e work that wen t in to making this 12 5 so meth ing close to the final expression of th e tuner's art in the ligh tweigh t fie ld . Fo r opene rs, the front of th e fram e w as he avil y gu ssc tted an d an ex tra su pport ring w as in stalled 10 keep th e forks fr om loosen ing d u rin g MX co mpe tition. The fr a me w as re pl ated and p olish ed a ft e r th e welding w as com p le te. Th e e ngi ne h ad a GP cran k ins talled 'fo r rel iabili ty a lo ng wi th a n o ld- sty le gea rb ox, which is b oth ligh ter and is closer rati o . All m oving parts in the engin e have been pl ated with a superha rd ch ro m e com pound to reduce in lem a! frict io n by an estima ted 15 %. Th e sc oo ter h as a Mo toplat ignition, a n ov elty fo r th e 12 5 Zundapp but someth in g that is in th e o ffing for stocke rs. The b ore has b een taken o u t t o 55mm an d th e h ead rew orked to fi t the charac teristics o f this p articular engine . It breathes th ro ugh a 3 0m m Bin g with a reed valve . Th e Yamah a re ar ReeJ l1=y whcel assembly provides it cushion drive for the bike to take the load off the ligh ter , close ratio gearbox. This, in turn, req uired reworking- the brake and brake pedal h UI still allows in te rch ange abili ty, going back to a Iigh te r Rickman huh for IT co m pe titio n. The frame was al so gussetted at the shock mounts to preven t any frame tweaking from loads trans mitted through ' the Koni shocks. Whew ! A rc yo u re ad y for a ll th at? E .C . Birt was and he 'll do it for a pric e an d the ch allenge, th e challenge of d o in g it righ t and b u ild in g th e faste st Rickman s in the \l' e st . May b e , just may be, the fastes t 12 5 s any wh e re. Is it all w o rth it? If you 're re all y serious about w in ning, or your spo nso r is, an d you' re good enough , the n it definite ly is . All that S tage III tri ck stuff docs make a difference. T h ough not expert riders (or we wouldnt b e noosepaper guys) , the C. '\1' slaff gets on a lot of different bikes and knows th e feel. To a man, every test rider stated in agreement that the Birt-prep ared 125 Rickman had all the speed and power of a 250 European motocrosser in close to stock trim . \l'hen you wick it, it immediarelv feels like a 250 and th e pipiness is ~onverted to something more like a surge of power. It's a lot of work to get it that way, but it's a very imp ressive m o tor. \ Thi s is the business part. E.C. designs and makes characteristics incorporating Soundma ster silencers. Th e ported cy linde r. Work ing with the ch rorn e-Hned barrel requ ires ski ll and the right tools. own pipes to compl ement engine Dal e Herbrandson of DH Enterprises, form er McCu lloch engineer, designed the reed valve for the Zundapps. Th ey are made of linen phenol ic material wh ich is digest ible if the reed gets sucked in. Th ey w ill be on the market in about a month . if you need one, for the Bing. Ama l concent ric or28 m m M ikun i.