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/125872
Fast women E.C.. I've got a p roblem. It 's my ne w motorc ycle. I'll call him lIusk y. He 's a perfect size 125 CR with a y ello w ta nk and perfect ma n ners . lie 's th e lat est model (1 9 74) you kn ow. w ith th e ribs bracing his coo ling [ins, 3 2 m m Bing , and I'm told h is in t ern als are bigger and b etter than t't'er ( large cran k and etc.]. I' v e got him t ricked ou t. f rom al u min u m c l u t ch, small reversed .\lo t oplat to an air inl et horn f rom a 250. Th e stinger has been modified. b ut all h is p orting is stock. Well E.C.. th e problem is th ese two "racy w o men " h e's b een ha nging around with , Elsi e and Su zi e. Though t hey di spla y ver y poor ma nners (do n:t see m to b e a b le t o ha ndle th em sel ves if yo u know wha t I me an), th ey're co nsis ten tly over-p owering m y [rirnd ty lIusk y. His co usins in th e b ig city and Europe d o n 'I see m to ha ve th is problem . Hoto can 1 teach th e co un try bump kin to o verc om e his g utless ness ? I'm racin g him at 4.300 f eet so one problem is he's o ver carb ure t ed; t hey tell m e that a s maller Mikuni, e tc . will starve h im a t high RPM and he's a rev ve r. t hat's f o r sure. Ma y be a reed -oalue l Or will 1 have to have him operated o n ? I can't afford to lose the reliability my friend has gi ve n me. Can y ou help. E. C.? . Got a technical problem that needs expert advice? Send queries to "A sk E.C." c/o Cycle News. Your reply will appear in the paper within a few weeks. Hard questions may take a little lonl,ocr to ans wer, Honda radial heads -, Th e bike is a 125 Elsin o re and th e question is: What p erf ormance gains can I ex pect with t he addi tion of a high co m pression radial head and a to rqu e pipe s uc h as th e o nes from D&G Performanc e or N orris Roberts Honda ? A Iso w ould th e high compressio n h ead be any harder o n th e m otor? 1 kn ow th e .ltT 125 pist o n w ill gi ve m or e low end gru nt if ins talle d i n th e Elsin or e , b ut how w ill it af f ec t th e mid-range and top end? Jo e Jamieson Gard en Gro ve. Calif. [ don 't know about these heads or pipes (excep t that [ th ink they're both the same) sin ce [ haven 't tested them. But we will find out for you in the near future. I'm moving to Florida, sh o uld be there in about three weeks, because of com mitments to Mai co , Zu ndapp , Tyran , Steen's and Webco. I wi ll be writi ng a ne w column, "E .C. 's Test Bench." T his co lu mn will be direct ed toward tes ting of all t he new hardware products on the m ar ke t. If th e produc t is good , I' ll let you. th e race r-reader, know. If it 's bad . ['II let the manufacturer know, give h im a chance to make it righ t. and then re-t est it. , I Products will be tested two ways. Anything that pertains to horsepower will have a complete dyno run . Ch arts will be kept on horsepower readings and engine tempe rature s. (Yo u can pick up a lot of horsepower o n any engine by just raising the compression but when you get it to the track you wind up going slower t han a stocker if the compression is too h igh .) The final check will be on a racing bike in competiti on under one of my ride rs . These 12 riders have jobs to do : first , and most important, to test racing products and give me the in fo rm at ion to improve t he products or pass along to you t hat it is a good pro duct, worth using on your bike. Second. win races . It it's street bike goodies or safety equipment. t hat will also be tested , o n road bi kes. You're righ t abo ut the MT pist on . lt will give you a lilli e be tter bo ltom end torque bu t will h ur t t op end hor sep o wer co nsiderably. I'm work ing on a tech article no w on all t hose neat tric ks for th e CR 12 5:\1 Ho nda to get extra ponies . Zundapp 30 I have so often h eard yo ur "a m e affiliat ed with th e w ord Z undapp that I f eel that you must have a very intimate knowledge and understa nding of these engin es. Rec e"tl y I purchased a '73 Rick man-I Zii MX after having o w ned a Zundapp 100 Scrambler and ha ve acquired an extrem e fo nd ne ss for these bikes. 1 have no intention of racing th e Rickman. but bought it primarily th e basis of R ickman handling and Zundapp durability, to us e 0 " cross country treks in th e mountains. N ot ha t'"g a great d eal of ex perience wit h two st rokes a nd lack ing a t horo ugh unde rs tan d ing of Zundapp engine s in particular, I'm writing t o d raw upon yo ur experie nces with these engi nes so that 1 can b ec ome more familiarized with all the id iosyncracies of th e Zundapp 125. 1 ha ve alread y -had t o disa ss emble t he engine and replace th e ge ar se lec to r rod and se lec to r s haf t bearing race (righ t cov er) . (Had a problem with a ro ck that was bigger than yo ur Zundapp, didn 't yo u? . . . E.C.) N ow tha t th is pr oblem is corrected , an Enduro Kit added. and th r engine nearl y brok en in. I w ould lik e to begin sorting o ut t h e carburction for i t appears to be ° nning ext re mely rich . ru (It is rich ... E.C. ) Do y ou recomm end an y particu lar jet sizes and n eedle setting and h o w much ca n I d eviat e f ro m th e initial f acto ry se tti ngs witho ut harming th e eng ine? Den ver 's 5. 20 0 f eet ab o ve sea le v el. A ft er f i t t i ng , a Skyway s ile ncer /spark arrest or co mbination . m ust the jetting b e altered an d wh at effec t will th is ha ve o n p eak inessr (T he Sky will hurt yo ur top end a little hit but not enough to bother y ou ... E.C. ) A lso, wh at can 1 d o to broade n th e p o uierband witho u t a great dea l of expense? Do yo u handle t he Z undapp bik es and parts ? If so , please se nd all th c info rma tion you can spare o n th e m o r a list an d prices on your offerings. 0" Karl Dallarosa Wheat Ridge. Colo. I think my Bing carb tech will hand all your jetting needs. A very big Zundapp Tech article is in th e making and [ t hink it will han dl e a ll yo ur questions as far as horse power needs go. You sho uld see it in Cycle lVl'WS next week. Yes, we do carry the ~undapp s in Florida . We have a full inventory of par ts and will mail order any part needed to any place in t he world. A ll parts o rde rs go ou t with in 24 hours aft er placed. E.C. & Walker Dept. Zundapp 5 09 Ind ust r ial Avenue Boynton Beac h , Florida :134 35 Phone 3 0 5/ 73 7-69 17 o r 3 05/73 2-18 9 0 Husqvarna Bumpkin R eno, Ncoada Maybe no thing shor t of major surgery will fix the problem . Somebody u p t here in the big doggy land where Huskies come from ble w it. Let's see what we Can do to help his problem . The 1974 Husky engine is totally different than the 19 73 Husky. I've had other people call me abo ut this problem also, but I haven 't seen o ne of the engines or had a chance to make a layout o f the 1974 125 Hus ky. So I called my very good friend Dr. David Hagg. His sons Bobby and Steve have been riding fo r Husky fo r t he las t couple of years an d t hey have been working with the 125 Husky since it firs t ca me into the United States . I asked Dave what the stock port ti ming of the 1974 Hus ky is. T his is what he [aid on me. With an exhaust tim ing of 78 degrees . 3 5 degrees of blow down and 175 degrees of intake. Whic h all boils down to one thing, th e engine is just too far on t he road racer side for mo tocross un less you are one super ride r and can keep t he engine in the 10,000 t o 10, 5 0 0 RPM range. Anywhe re bel o w o r above yo u have zero ho rsepower. Wbat can we do ? Firs t t hing, ta ke that trick Mo to plat off. [f any th ing, you need mo re flyw hee l weigh t t han yo u had stock so that whe n yo u do ge t it up to the point a t which it makes horsepower . it will s tay there. Then change the gearing to lOon tbe front and stan with a 60 on th e rea r. You 've got to have it geared low enough so tha t you can use all s ix gears. With this port timing two mo re gears wouldn 't hurt you a bit. Next c hange your carb to a 30m m Bing. It just won't ta ke a 32mm carb and give yo u an y to rque (d o n 't use a :\Iikuni). In the 3 0 mm Bing 1 would use either a 5 I ·59 1 o r a 5 I -5 9 2 vaporizer. I think that the 5 1-595 th at the carb comes with will be too rich a t y our altitude. Stinger size should be somewhere around seven-eighth inch size. ' Check your kicking com p ression. You need so me where in the r.. ge of m 165 to 175 pounds. Don't ru n any more than the I i 5 pounds because it wi ll keep the engi ne from revving. 1 recd va lve wo uld help but i ts not \ go ing t o be the answer to the pr oblem bec ause the e x ha us t port is j us t to o b loody high. On ce thc meta l is gone you ca n' t put it ba c k o n. . . Do a ll o f the above things first. Then - if tho se 1w o little sweeties are still giving you a problem. watch Cycle N ews for the time when I will be in F lo rida. Send me yo ur engine co m p le te and I will rede sign it co mpl et ely . make a new cylinder liner for it and make it int o a reed engine. Then we will tea ch those two huss y women a les so n. The mysterious DT360 detonation caper so lved - or sidestepped lI'e ha ve b an ent irety baf fled as to ho u . t o slo p d ct o natio r O il t h ree differen t 1974 Ya mah a 360 Endure s wit h COl ig nitio n. Th e dealer has pr essur e-t est ed the entire engine fo r any air leak s tw ice. with negative results. lI'e ha re tried virtually all brands and grades of gaso line. NGK plug heat ranges f ro m i · 10 an d ma in Je t sizes from 160 to 23 0. A11 to no auail. The new mod el appears to be co m ple te ly o b liv ious t o th e o cta ne ofth e gasolin e. It co n t in ues to d et onate wit h th e lowest oc ta nt' regular to th e high est o ctane available fr om a gas pum p . Th e timing has also be en pr ecisel y se t t wice b y th e dealer. and th ,'Y ha ve do ne their best to solve t he pr oblem. (A p paren tl y• .llitsubishi w as over f rom J apa n. lr yin g t o so lve the pr oble m al Ya mahu l ntl. rcccntly. ) Cunt ac t w ith t hem has result ed in a stopg ap cu re : pla y ing wit h th e timing m ar ks. IloW CZ Jl7. CVC 1l th is IUlJ nu t really solued th e pr oblem yet . Do w c n eed a ,,,' w timing lighl ? Is tlu: CD I unit th e cu lp rit ? Can it be modified t o Slop ad vancin g t h e spa rk at th e corre ct R I':I/, if it is t o blame ? Mean wh ile, thes e bik es just -keep o n d eto nating, pingi ng. o r making high speed rattling so unds (like ball bearings b e in g shot ar o u n d insid e th e comb ustion cham be r) bctuicen f our and six th ousand RI'.ll. Peak d et onation occ urs at 5 40 0 RI'.I!. The ne w DT360.. may be lead an ch ors but they 'rc still the best end uro bike Yamaha has built yet. It 's to o bad su ch severe det onation spoils its co m ple x ion. Can anything be done, E. C. ? Yamaha should never ha ue let th is one o ut so soon. Bill H emdo n Gl endale, Calif. Bill . yo u're nOI the o nly o ne baffled abo ut t he problem of detonation in the DT 360A Yamaha Enduro . Ya maha would also like to have the answer. :\Iay be the y have it figured out by now, but t he followin g is what I came up with. The ca rb that co mes o n the bike is a 30 m m ca rbo I think that Yamaha chose that because they were trying to get better gas mi leage. whic h has proved t o be Mistake No . I. But before I get into th e carb, let's touch on the ignition first: the CO l t ha t co mes o n the bike. There's no way to really time it wit h th e timi ng ligh ts that we have in the Sta les. Just se t it to wh at th e fac tory ca lls for . If th e tim ing is st ill erra ti c, the n have yo ur dealer send it back to Yam ah a. It's covered under warraruv . Now back t o the c:{rb. I went over to llarry foste r's Yamaha and told them abou t the problem y o u were hav ing. Harry said yes . the re was a Yamah a 36 0 in the sho p right now that had a problem. You bet it did. It had a fun ny five port hole right through the top of the piston . So Ron. o ne o f the mechanics. said that he would wo rk with me 10 see if we could fin d T he Answer. First, we pulled off the carb and look it apart. This bike had less than 50 miles o n it and had not been touched. It was ex acrly the way it came from the fact o ry . First thing [ no ted was the carb was o nly a 30mm Mikuni. .\ ha ! This had me o n guard right from t he sta rt. Taking the ca rb apart, [ found that it bad. stock from the facto ry, a 5FJ8 needle (with the clip in the second notch from the bottom); No . :1 slide cu ta way: 24 IOX needle je t, No. 50 pilo t jet and 180 main je t. 0 The next s tep was to m o to r up to Suzuki City and have Gene go through all his jets and come up wit h some needle jets and need les fo r me. We figured o u t righ t off that the small cur b was j ust to o littl e . but we 'd give it the benefit of the doubt. We chose 6 1'8 , and 6F4 needles. In need le jets , we wen I fo r a 1'-0 and a 1'-4. For you sha rpies t hat ju st caugh t me and a re saying. "Ah- ha h! Thuts no t th e right nee dle jets for the side mai n je t ca rb l; " Yo u' re right . the y' re no t. With the se jets. you use the regular Mi kuni je ts and jet the earb off t he bottom of the bowl. leaving the je t