Cycle News - Archive Issues - 1970's

I (IJ • , , ,, , , 51 a: IilI , , ) • , ~ , , IilI , ..:::lI CO» , , ;... CO» , , / , , -er- , , C'l -e- C'l ... :; / ...0 E ... I <:J .... c, I a; rf.J If dual reeds, dual carbs was the hot setup for A Super karts ten years ago, it ought to work on a bike, huh? It works, and psychs the opposition as well. / I The complete k it, less exhaust pipe. Plans to market the conversion are in the works. Blow their minds and blow them into the bushes at the same · ime! t Kaw 100 double pumper reed conversion By Arthur Ridderhof Since the 10Gcc Green Streak was discontinued In 1972 parts have been progressively harder to find. Luckily, parts from the other Experimental Kawasaki port models 8mm F 9 degrees G ='!}={ \/----" t With our experimental Kawasaki we wanted all or at least almost all parts to be available over the counter, from local dealers, so that no foreseeab le parts hassles would keep us out of co m peti tion. The engine: 8mm 0 i -e.s .L mm ' " , boundary o f silicone rubber aro und th e insid e of th e ro tary valve cavity. Th e m o torc ycl e was d esign ed for IT-scramb les, so we were ab le to go to the maximum on almost everyth ing . The exhaust port was raised six mill imeters and widene d to 80% o f th e bore . The m ai n transfe rs, beca use of thei r already large size. were kep t stock on ly re-d irec t ed to a nine degree up draft. The rear transfer port was raised 4.5mm and wid ened 16 m m . (See Fig. 2) Unlike most reed valve co nversions, this one will wo rk without any vent holes in the piston, because the ree d valves feed through the botto m of the rea r transfer port. The rear boost port is fed d irectly by th e ree ds, as w ell as th e crankcase fuel/air mixt u re, as shown in Figu re I. The ex haust system is on e used in ro tary valve Ka wasa k is wi th a few di mensions al te re d to make it more co m pa tible for i ts ne w reed valve app lica ti on. (See Fig. 3) T he e ngi ne uses a s tan dard T rail Boss fly wh e el m a gneto, with th e not -sa -stan d ard ti m ing of 2.3mm BTDC. . Th e p oin t ca m was Kal -garded to keep th e ignition area t otally free o f oil. Ligh tin g coils wer e rem oved to d ecr eas e some of th e m agn e tic pull o n the flywheel, as well as appro xi m ately tw o and a hal f pounds of needless weight, A ll un necessary engine castings were re moved and trim med back to a minimum. T his was done mainly to re d uce weigh t , The clutch is a standard Trail Boss unit which shares the same part numbers as the Green S treak 100. The whole kick starter and ratcheting assembly was re moved, saving three and a quarter pounds. The entire engine received the Kal-Gard treat ment to minimize internal friction and hea t buildup. We found that the Kal-Gar d treatment reduced heat conside ra bly and probably gained horsepower at the rear wheel. The process is avai la ble through our faci lities at Two Stroke Continued 0" page 42 For m a ny years it was felt that th e rotary valve was the most efficient method of induction, eve n mo re so than the reed valve. The two strongest objections to reed valves were: (1) lack of throttle response, usually m a kin g it mandatory to install a larger carbureto r. etc. (2) the physical restriction of th e reed itself. The first prob lem was the easiest t o solve; use two large vent u ri , p um per carb u retors d esign ed to w ork a t low velocity (the 34 m m McCull och 9 1 A, B or C series ca rb ure tor). The second pr oblem (ree d restriction ) is partiall y solved b y m odem 4v reed cages which are more ae rodynam ic nan flat pla te or sq uare p y ramid ty pes. We wen t one ste p fur ther b y doubling the number of reed s to cut velocity through the reeds in hal f. T hen modifications to allow the carbu retors to operate at t h is new lowe r velocity were applied to the need le seat level and needle valves. So much for theory - after the rear portion of t he cylinder was milled off and our fabricated reed manifold was welded on. we had to block off the rotary valve port. We also had to find a way to keep the primary compression from leaking past the right side main bearing and dissipating out into the rotary valve cavity. The rotary val ve port was filled with epoxy and shaped to match the transfer cavity o n the opposite side. Provisions were also made to lubricate the bearing. To hold the pri m ary compression. we used a o n e -s i de shielded bearing and a Fig. 2 small-bore Kawasak i models arc re ad ily in terchangeab le. Some owners have even gone so far as using Suzu ki cyli nders and/or ' Honda pistons, etc. ..:.L , 3.8m m " " Heig ht of pist o n crow n 1'~1 .., 7 .25 " I at B.D.C. , .5" dia. Fig. 3 100cc reed valve -rJ~ICI -- ' .2 ··~ 6 .5" 8 .35" ~((t\Lj.l~tl((a.ua.rr .:",.....: t::.::: I .:,:. ... '- , I r .~. ",. -cart f 1 7/8" dia , 3.00 " dia . 2 ..00" ~ 3.45 " dia , dla .. " 3 .00" dia . Experimental Kawasaki 100cc reed pipe 2.5" d ia .

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