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/125877
_.- - - . -- - - ----,= - - - - - - - - - - - - - - The completed reed valve set up. E.C . like s Bing carb s. - The rad ia l head ' s combust io n c ha mber, and ... . . . a view fro m the top . . -.;...- - - - - - - - - - - - - - - - - - - - - -, Photo A. Now let 's look at the point that you are a better than an average rider and don't think that the reed is really what you want. You can c h oo se the Honda optional racing cy lin d er , manifold, carb and pipe. This cylinder from Honda puts out some pretty resp ect ab le horsepower. The Honda racing cylinder has a back port in it that the sto ck cylinder doesn't have. This back port is fed fro m the two side transfers. Third ports There 's another way of doing y o u r stock c y lin d er that I like better. This is in the style o f the factory third port d esign like used hy Zundapp in their works b ikes . (See Diagram Two.) This third port is fed by a port in the piston. (Diagram Three) If you use the st ock pist o n you h a ve to put this port in the bottom ring land and th e piston wit ho u t this ring which isn 't to o good b ecause you lose too much of your charge around the ring land w ith it being open. With the dy ke piston th e port goes u nde r t he dy ke ring. T h is port does two things : (A) h elps fill the back of t he cylinder; (B) keeps a fresh c h ar ge of gas and oil passing over the top of the rod bearing and a lso help s cool the lower side o f the piston dome. Cooling, is one of the spots wh ere the little Ho nd a has a problem. ( Like when you're ha lfway through y our moto y o u can feel your bike is j us t not pulling like it was at the sta r t. Th is horsepower loss is due to too much engine he at.] T he 100cc Elsinore kit b u ild s the bes t stock 125 into the be st 1 00 c lass motocrosse r a ro und . The y haven't been beat yet. Pho to B. T h is sp ecial exhaust f lange is worth yet another tad of horsepower increase. unbrea kab le r ing. The piston starts o f at standa rd a t 5 1mm an d I did this becau se I know t ha t a lo t of you have 10 0cc e ngi nes no w a nd are o ut of p isto ns . The last o ver size is 5 2mm. T hese 100cc kits can be o rdered in th ree st ag es. Stage One is lin er and pi st on for piston p ort. Stage Two is liner with reed por ts a nd p ist on with reed p orts. St age T h ree is a fa ctory th ird po rt m achined into th e liner and a piston with the th ird p ort in it . If you have a way o f m achining the ports yourself the st age one liner kit co m es with p orting spec s and in stru ctions th at will te ll y o u ho w to build any s tage. You don't have t o buy t h e com p le te kit just to ge t a pi st on. Pist on o r lin er can be purchas ed separately. Kn owing of some o f th e p roblems tha t a rrive d with so me of the o t h er kits th at h ave been sold I've ha d this liner ma de a little bigger on t he o utside d iame t er so you can rebore y o ur cy lin d er an d save that top en d . It's impo ssible fo r me to inspect yo ur cy lin der over th e p h o ne but if yo u wan t to ha ve me inspec t y ou rs send it to Florida and (' II advise yo u on wha t to do t he best way I kn ow how. Th ere is no c ha rge f or this servi ce , I'm he re to help any way that I can. Wh a t kind of horsep ower d oes this kit put out? 1 hav en ' t had time to dyno it . b ut we haven't been be at yet by a nyone. As soon as I gel to Flo rida I will star t wo rking o n a foll o w up a rticl e on this little screafuer and will tes t all the go- fast good ies o n the mar ke t fo r the 12 5cc Ho nda tha t we ge t . A ll you tuner s o u t ther e in Honda land. se n d your trick Hon da stuff to E.C .'s T est Ben ch, 50 9 Indus trial Ave ., Boynton Beach , FL 33435, with p rice list . Phon e numb er s of the hoi tip shops in l.os Angel es : ,-~---------=-=-------------- --_. - run Radial heads When s o m e of my Hondas first sh owed up a t a race with a radial head, it wasn't just for looks. With th e stock head machined to bring up the c o m p re ss io n ra tio to where I wanted it the engine pinged and detonated very b adl y. The d yn o he at ga ug e also showed that the he ad temperature was way too high fo r the engine to live long. One of m y Zundapp r acers was sitting in the co rn er and I said , " T ha t Zundapp head w ill help the p roblem," so I proceeded t o s tea l the head from it and headed for t he machine sh op. Four hours later I had it so it would fit the Ho nda. I felt th at with the diffe ren t design combustion c ha m be r and much better cooling it would pay o ff. Back to the dyno to .ge t ano th er power ru n to see if my t hought s were right. Well , t hey were, wit h almost a full horsepower gain everywhere an d th e en gine temp dr opped en ough so tha t a l the end of a m ot o t he bike was still pulling stro ngl y. This was th e star ting point almost a y ear ago. I.ast we ek we sta rt ed shippin g pr oducti on rad ial E.C. heads. It to o k a long tim e but I wa n ted and in sisted th at t he E.C . h ead was h etter th au the "! w > '" l/l o o lo- I c. Zundapp head and I wouldn't re lease it un til it was . With y o u r engine built in to a reed engine the stock pipe works well wi t h one inch c u t o u t of the he ad pipe for experts. For juniors leave it alone. Now, if you 're still looking for mo re horsepo we r it ca n be ha d in a pipe ch a nge . J & B in Ari zona ; D G Per fo rm a nc e, Flying Machine Fac t ory, Preci si o n Cycle a n d Bassani in Los Angeles a ll build very go od pipes fo r the l lo n d a , My reed pipes o r piston port pipes are huilt a nd tun ed 10 fit th e needs of th e engin e a n d rider they are goi ng to. We als o have a sp ec ia l exhaus t flange whi ch is worth a to uc h m ore horsepower fo r those wh o n eed it. Th e Honda en gine wei gh s in at 4 4 pounds o n my scale, whi ch m ak es it o n e of t he lightest en gines o n th e mar ket. With its su p er light c ran k an d m ag, plus the fac t th at it has a 50 m m st ro ke makes it pe rfect to slee ve d own into a 100cc m otorc ycle. There has been a 101 of demands f or kits like t his hut most of th e m weren't too good and t he bi gges t pr obl em has been t hat t here has been n o pis ton yo u could buy and con ver t with ou t a lo t o f tr ouble. l OOcc Elsino re Kn owi ng of t hese pro bl em s I h ave since d esigned a 10 0cc k it t hat should fit m o st ride rs' ne eds . T he E.C. 10 0ce lI ond a pi sto n is also a fo rge d one ri ng d yke racing pi ston usin g a Poppy DG 71 4- 6 3 9-70 2 0. Fl yi n g M a ch in e Fac to ry 213/530-4656 . Pre ci sion Cycle 2 13 /370·9978. Ba ssan i 714/630- 1821. J & B Glend ale, A rizo na 602/931-9235 . E.C. & Wa lke r, Boynton Beach , Florida 305/737-6917 or 73 2-1890 . • 29