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/141064
o N " '" ~ Review: uTw o Stroke Tuner's Handbook" Distribu ted by Webco Pap er , 156 pp. , $2 .9 5 C"l .... e> N '" ;: w Z W ...J o > o by Ron Schneiders Gord on J ennings ' new b ook , "Two ·S tro ke Tuner's Handbook ," po ssess es a unique ad vantage at the o u tset: By its mere e xi ste nc e it is the "best " be cau se i t - is the "only ." Furthermore, th at it is ver y b adl y needed is evide nced by th e number of broken scooters with h oled pistons found after every de manding race. The tw o -str ok e engin e , unlik e th e four-stroke, is relatively easy to ch ange. A significan t ch ange can be made with a $30 grinder and a handful o f stones. Bu t will it be an improvement? Can ' th e ch an ge be balanced with other needed ch an ges so th at the system wo n ' t self dest ru ct ? Most riders in co mpetition eventually decide to "improve" their engi n e becau se they know -th a t the en gine can be mad e faste r (t heir co mpetitors' are) and b ecau se it's "easy" - t o d o (in th e strict ly m e ch an ical sense) . T heir kn owl ed ge, tho ugh , is bi ts an d pieces, a m a g a zin e a rticle h er e, a chance cam men t ove rheard, th e earnest advice of a frie n d. N o on e is b orn with the ab ility to tune two-s tr ok e engi nes an d un til n ow th ere h aven ' t been any good . boo ks o n the subject . J enn in gs ' b o ok corrects th is sit uation. He very me th odicaily goes th rough each section of the engine, an d eac h p ar t of th e o peration and ex plains the p rin cipl es involved, n o t only in the stock mode but in th e race m ode. In simple te rms he de scribes th e limi ts of ma ter ials, how to d e termin e those limits, and h ow to extend them. J ennin gs explo des a lot of popular myths such as t he n otio n that if an 8 : I co mp ression ratio is good, a 16: I ratio is better, an d the eq ually popular notion th at the biggest carbureto r y ou can fit to the cyli n der is th e best . His primary thesis is that any idio t can get more power out of an engine by simply ma kin g it rev faster. T h ere is, h ow ever , a limit imposed b y ma terials on h ow fast th e engine can rev without des tr oyin g itself, so the w o rk of the tuner is to in crease p ower an d powe r b and with out ex ceeding the me ch an ic al limits of the engine. T his the me is carried th roughout the book and if the maj o rity of hom e tuners absorb no thi ng but this messa ge from the book, they will have received go od valu e fo r th e $ 2 .95 purchas e price. There is much more to be h ad , howeve r: Occasio nal ly Mr . Jennings gets turned on by his material and when he does the result is reall y beautiful. His descrip tio n of what . ha pp ens at th e mo men t o f co mb ust io n (p age 35) can n ot fail to give an y reason ably sen sitive tuner a greater insigh t into what is happening ins ide h is engine , which is th~ first n ecessary step toward co n trol, T here is en o ugh material in the b ook to en ab le a would-be tuner to sta rt modifying h is engine and be assu red of good results. Many of the pitfalls are de scribed and the measures to avoid them ' are care fully ex plained. Perhaps one of th e mo st sign ifican t aspects of th e book, howeve r, co ncern s that wh ich is no t said. Mr. Jennings is very careful to n o te when he 'is on solid ground and when he is o n the threshold of either his own knowledge o r the state of the art. This is extre me ly valuable to any seri o us tuner b ecause it e nab les him to know j us t whe n he can proceed quickly , and with co nfide nce , and wh en h e must exercise extreme cau tio n. Two-S tro ke Tuner's Handbook is not a perfect book, of co urse. Man y questions are raised but not answered, particularly q uestions pertainin g to specific bits and pieces of h ard ware. Whe n you get to the en d you wish there wer e fo ur or five mo re chapters . Bu t perhap s Mr. J ennings is ' pl anning a second vo lume or a se q uel. T he bo o k is sufficien tly wo rth wh ile ' th at it should h ave been given a be tt er , e ditorial and proof-reading effort. Bro ken type abo unds. T here are so me inaccuracies th at should have been picked up by th e editor, such as an inc omplete sta te me n t o f Boyl e 's law (no c o n si de r ation o f vo lume ) and a co m p ressi on ratio given as " zer o rzero " when th e pi st on is h oled. Actually, it is 1: 1; ze:ro :zc:ro is math ematical nonsense. This migh t h ave been a J enn ing s attempt at humor, but if so it isn' t sufficien tly cle ar. J en nings has stated several times that he d oesn't lik e mathema tics: th a t this is th e case is q ui te evide n t in hi s bo ok. Formulas are given with n o a tt empt to . explain o r derive them so one has no wa y o f ev alu ati ng their validity. Som e of the formulas are a bit susp ect, at least mathema tically . One, for instance (page 56) states : L equals ExV over N. The units on th e left side are inc hes, the uni ts o n th e right side are degrees, feet . per secon d , an d revo lu tions per minute. These will approxim ately can cel o u t if on e converts the min utes to seconds (o r vice versa) an d the degrees to radians an d doesn ' t mind th e fact tha t 3 doesn't exactly eq ual 3 . 14 16. Bu t th er e is still a factor of 12 unaccounted for. J en n ings suggests that the tuner use a wave speed o f 1700 feet per second, but no tes the results migh t not be precise. Since that 1700 is not only wave speed but constan t and fu dge factor as well, I don't wo nde r that the result s aren't ne cess ari ly precise. T hese c on side ra tio n s will not a ffec t the p ractical tune r wh o is working with a grinding wheel and a wel din g torc h, bu t for us tuners wh o would ra th er build engines with a slide ru le in the comfort of o ur livin g ro oms, a few more o f the mathem a tical nice ties would be ap preciated. In his preface Mr. Jennings gives credit to an engineer who " diluted h is ignorance ." Mr. J en nin gs' book shoul d in tum do mu ch toward diluting th e ignorance: of m a n y n o n -e x p e rt tw o-stroke tuner s. Begin ners should be required to rea d this book before the y are p ermitted to touch a cylin de r with a grindin ~ stone or an e xpan sio n cha mbe r with a welding to rch. In Defens'e of Those Other Enduros b y Larry Langley , of the URA In a re cen t Cy cle ews, Ron Schneid ers, in his . Gambit column , wo ndered wh y the Shamro cks d idn't pull more ride rs to their enduro. Then h e we n t o n to whine an d moan abou t th e " Pro mo te r" type of organization which pulls ma ny more riders to fami ly -ty pe en d u ros. I' m n or sure if Ron was using a hypothetical organization o r had a particular one in mind b ut I do object to him lu mping District 3 7 clubs in o ne gro up an d th e p rivate promoters in another. T his is as ba d as say ing all m oto rcy clist s are "alike. I fee l he was w ay off in his co ncl usions. You see , Ron su ffers fr om wh at I'll call the Di strict 37 . sy n d ro me. This is th e be lief th at on ly a Distr ict 37 club can pu t o n a ch allenging , champion shi p en d u ro . Ron states in his colum n that promoters run the rid e rs over worn ou t trai ls wit h marginal marking an d suc h. I have b een on so me en d u ro s over worn out trai ls ' with marginal marking. A co uple were promoter organized and a co uple were District 3 7 sponso re d: I am a partner in United Racing Association (U RA ) and als o bel on g to AMA an d Distri ct 3 7. I am n ot an ti-Dist rict 3 7 b u t I d o objec t to bein g lumped together and h avin g barbs thrown at me. R e garding the Shamroc ks only pullin g 2 8 0 riders, I heard it wa s a bi tchin ' en d uro and pl an on riding it n ext year. H owever, an en d u ro m us t b e properly p romoted regardless of who is p utting it o n. This in cludes adve rtising' in Cy cle Ne ws, flyers to all th e clubs and b ike shops , and listing th e eve n t in the calendar sec tion o f Cycle News . How many times have y o u fo un d jou t abo ut a Distric t 3 7 end u ro by finding it in the cal endar secti on . Sure , the sche d ule is p rin ted in advance, bu t th e non-district 3 7 rid ers d on ' t kn ow about it. URA an d SRA are two prom o ter types who main la in a mailing lis t o f all the rid ers who eve r ro de on e of thei r even ts. \\rhen a n ew e ve n t co mes u p we p rint up lab els an d ma il flyers out to all th e ride rs ' on the list. How man y cl ubs take the time an d effo rt to do th is? T he flyers sho uld accurately indica te ho w diffi cu lt th e en duro is go ing to he ; hard , medium or easy . Easy should n't be a c uss w o rd as lo n g as it's fun an d in teresting. T he promo tin g organiza tio n should make every eff or t to insure a safe ru n . an d this incl udes properly marked co u rses (rib bo n an d dan ger mar kin gs), com mu n ications a ro und th e co u rse , first aid and amb ulance servi ces . URA, for example , uses the In tern at ion al Racin g Crew (I R RC) for R ad io co m m u n ica tio n s, Service Searc h an d Rescue (SSA R) for first aid (Most o f SSAR members are highl y trained para-medics and h ave full y eq uip ped =- 4-wheel drive veh icles.) , an d alwa ys has an ambulan ce on hand o r the end uro d oes n ot start. At a rece nt en d u ro put o n by an organi zati on wh ich Ro n praised as being on par with District 37 , there were n o (repeat NO ) ambulan ce or toilets present. Ro n made mention in his article that th e promoter type enduros are generally run ove r the sa me old worn out terrain wi th n o rega rd for th e rider wh o h as pai d h is h ard earned mo ney . Well, the las t three Dis tri ct 3 7 en d u ro s I have ridden (2 of wh ich we re National End ures) we re ove r well us ed te rrai n. In fact , o ne of the endu ro lo op s was one whic h th e club used th e ye ar before but ran b ackwards this year. Als o at th e Last Chance Na tio nal End uro th e course was sabotaged , and Ron sta te d at the time that it was a sh ame , it wasn 't the club's fault , ever y one understood, etc. . Bu t if a promoter end uro gets sabotaged , according to Ron , it 's be cause of poor course marking, stupidity, e tc . Notice th e pattern . Also, it has now b een six months since th e Last Ch an ce , an d the club (CE A) still hasn't sen t fin ishing pin s or as far as I kn ow troph ies. If a promoting club -did this th ey would be o ut o f busin ess soon. I call it a rip off , pure and simp le. Why d o riders p ass up the Dist rict 3 7 en du res fo r the fa mily ty pe ? Firs t of all, th ere is no begin ne r clas s in AMA. The begin ners are lumped in with th e be tter .B riders so they do n ' t stand mu ch of a chance (If winnin g a tro ph y . Sp eakin g o f tro p hi es 1 h ave n eve r seen an en d uro with mo re th an 20 percent finishing t rophying. Since th e beginner riders ha ve a tendency to ride rather slo wly th ey cr eate bo tt len ecks fo r th e be ttes riders. I h ave seen th em ru th lessly kicked off th e trail so that th e ride rs would n o t be slowed d own . Sounds fun, huh ? Perhaps Distr ict 37 co uld co me up w ith a C classification and start them behind the 0 th ers. A lso , no p oin ts co uld be accu mulated unti l the rider is mo ved up to B class ; say after three end uros. As far as p romo te r o rganization s putting on q uality even ts, URA recentl y th rew the 2 50 mile La me Dog En duro fro m Desert Ce nter to Nee dles an d b ac k, S RA promoted the Cal ifo rn ia City Gran d Pri x after the Elsino re Grand Pri x we n t to Rive rsid e Racew ay , an d CRC threw a G rand Pri x at Ca rlsb ad. T hese wer e qu alit y ru ns, as k the rid ers wh 0 p ar ticip at ed . If eit he r a District club o r an organizer consisten tly puts on sub -part ru ns , th ey sho uld be made aware th at the ri ders will n ot stan d fo r it an d imp ro vem en Is th at must be made or th ey wo n't ride it next time . . And R on , in closing, if you think all p ro m o ter type enduros are too tame I'll glad ly res erv e a number fo r yo u in next year's Lam e Do g. NEW UNBREAKABLE LEVER NOW FR OM THE P E OPL E WH O F IRST IN TROD UCED T HE OL D F A SHI ON E D P LAST IC L EVER S T O TH E M OT O R C YCLE IN D U STR Y CO MES T H E A L L N EW M A GNUM MX LEV ER MA GN UM'S N E W PR I N C I PL ES O F E NG I NE E RIN G G IVES Y O U TH ES E_ A D V ANTAG ES : I . BE T TER LE V ERA G E 2 . L O N GE R C A BLE LI FE 3 . S HO RT ER R EAC H 4 . S TRA IG H T P U LL 5 . TO TA L DES IG N T O ELIMINATE ALL ST R ESS A ND W E AK PO I N TS THE ONLY LEVER DESIGNED FOR PLASTICS ALREaDY AVAIl ABLE AT BEilER DEALERS . DIHS~'r.lRDIBUTORS , .... -, INQUIRE: MAGNUM LEVERS (213) 830-1&00 GARDENA, CALIF. ..