Cycle News - Archive Issues - 1970's

70 an inch • • • 00 _ __ 1eW• • tt. Cantilever mount Stock 4.5" measured rear ax le travel 3.5 " measured rear axle travel Bottom mount forward Price 1 pair 12 .9" dampers 2751b.l in . springs after standard shocks wear out Total ROSE BOWL IN F.b, 16, '7 S o Ap' . 27. '7S PASADENA 9am to 2pm AHYOHECAH BEA SELLER ! $50-70 12 ·15 1 pair 11.9 " or 12 .9" mod ified dampers 21 00 Ib.l in . (or hea vier) spr ings Cons truct ion cutting a nd welding Price $62-8 5 24-HR . I N FO RM ATIO N , CALL : (2 13) 588-7310 Price 4" measured rear axle travel 1 pa ir 11.9" dampers ' 288 Ib.l in . (o r heavier) springs 2 Bolt-on mounting brackets (incl. spr ings) Tota l $50-70 Total $100-120 Min. $15 $75-100 0.0 )'Our ....... , . ....."'0 .....,. ') _ -+o fot oo _ '1000 ....... _ -'d" _ ~ . . . . . . ~ •• h !loel 10 . _ ....... . .. Olcl 0" _ lI'O ,,"CI . u ....' "" _ , " ooId "'. _ _ • • "' ~ )'Cie wooIoIl 10' .:xr ~_ 10< _ 010""'- .... Hd. _1_ .. porto _ _ _heAd All _ ._ _ $ 19G-220 _ . . - lK~ r ~~ "'en. .... ..., ...... ...e4_" ""'ttIT . . - -.I ..ll -de4 to._ _ c--"_ . - _ . "" s.. , ,. _ ol . ~ -.II • • • ~ CA_ING'SSHOW ~ ~ HIADQUAmlS _otfk~ .........n -= ~ cnsLS....... ' ,0.101 . . hoi .:27 . .......... CoIMnOo M27. [ $38 .95 $9G-110 "T his mod may requ ire modified dampers. If so , add $50 to t he tot al pr ice . oma _ _a,,, ...-sIa, (Zll) sa'·IUS (Zll) Sll-4SSI The next incr em en tal step is obvious : buy new da mp en. When y our o rigi nal dam pen d on't damp any more or did n 't da mp well enoug h to suit you in the first place, y ou can im prove su sp ens ion performance by replacing them with a better grade of co nv en tio nal damper . Among current favorites in the group of tw in tube oil -damped shock absorbe rs remain the KONI, at ab ou t $ 70 a set plus springs, and th e Boge /Mulholland at abou t $50 a set p lu s springs. There's even an intermediate step here, of course. If your particular brand of dampen are rebuildable and you can get the rebuild kits, you can rebuild the st oc k dampers. Then you're bac k to "as new" performance. If "as new" wasn't too red hot to start with, you haven 't gained much and you have spent some time and money . It's a good general rule if you do rebuild your originals to always fill the shock bodies with a better grade of damping fluid. Use th e Bel-Ray LT series gook, ATF, one of the silicone-based fluids , or something like th at. It'll generally work better even if it doesn 't cure all th e ills in your stock shocks. So far, y o u h aven't increased your rear wheel travel but you 're enjoyin g a better, more controllable rid e and none of the origmal geometry or steering characteristics o f y o u r motorcycle h ave been affected. The next leve l o f complica tion you can contemplate is moving the bottom shock mounts forward to a poin t on the swingarm directly beneath the top shock mount, actually offset just a shade to the rear. On our test bed frame this brought the bottom mount from 2.5 inches in front of the re ar ax le to 6.5 inches up the swingarm. A simple bolt-on bottom shock mounting bracket is being sold by Cooper Motors, the Maico distributor for the West , at a price of $38,95 a pair including springs . If y ou used 13 inch (or thereabouts) dampers in the stock configuration, you will need 12 -inch dampen when the bottom mounts are moved forward in order to fit in the Cooper bolt-on brackets while keeping the swingarm within some bounds of a reasonably level loaded configuration. The modification will also require heavier springs. If you were using 75 Ib./in. , springs before, consider so met h in g around an 88 lb. /in . rate now. Cooper provides 90, 100, or I 10. At the cost of • different dam p en, th e ne w sp rings, an d the bolt-o n mountin g brackets, t he rear ax le travel on th e test bed fr am e was in creased to fo ur in ch es. If you already hav e t he proper length d am pen an d proper ra te sp rings or ca n tr ade for them, the co st of this gain in rear wheel travel is co ns iderably less. However , co nven tio nal oil- filled dampers will w ear o u t quicker when mounted further up the swingarm and there remains the nagging possibility of bending th e swingarm. It never happened in te st ing them but, frankly, the two test riders are not very hard on machinery even in su bject ing this modification to in ten tio nal hard use. Maybe you are. The next step goe a little beyond th'es co nfi ne s of the average ho me workshop. You can retain the bottom shock mounting position an d weld a boxed bracket to the rear V-tube th at comes down to the swingarm p ivo t. The new bracket should be centered o n a line from t he rear (lower) mounting position to the point where the frame ba ckbone and front down tube co m e togeth er at the steering he ad . This line sho u ld the in it ially be determined w ith swingarm in th e position it will attain when y ou sit on the b ike. With in a very narrow tolerance, t hat swin garm position sh o uld be level with th e ground when the bike is lo aded. Unless y ou also weld up a new support behind the bracket on this same imaginary line y o u run a very strong risk of bending the frame at that poin t. Without an y fu rth er modification, 12-inch dampen will fit on the base of t he new triangle you have constructed. Again, springs of some heavier rate will required. Probably something be between 100 and 120 lb. jin. will end up suiting most bike and rider combinations. The measured rear axle travel with this modification was 4 .5 inches. Cost of this modification coven the 12-inch dam p ers , heavier rate springs, plus cu tt in g and welding of the new bracket and support bar. You will have effectively ach ieved a cantilever design similar in appearance t o that on t he 1975 GP Husqvama, Penton/KTM, and Montesa V-75. Shock longevity is very adversely affected, if you are using the c o n ve n t i o n al oil-damped shock absorber. The cost of increased capacity shock bodies or radiator attachments should probably be figured into th is mad." •• • • •• • • ••• ••••••• •• • •••• •• On the frame of the test bi ke, it proved necessary to cu t and re-weld th e rear V·tube in order to acc o mmodate 13-inch shocks while retaining the stock bo ttom bracket. The addi ti o nal cu tting and welding costs (un less you have the eq uipm en t and skills) resul ted in a measured rear axle travel of 5,5 in ches. Some type of modified oil- only damper or a more expensive gas-oil damper proved to be a necessity for any serious co mp eti ti o n, such as a 30· mi nu te moto, or other prolonged, high stress riding. Welding and cutting labor was estim ated at $75-100 incl udi n g the little bits of metal that had to be cut to fabricate the boxed bracket and the T hen let Rolf Tibblin support. The price for modified oil and M ickey Quade dampers (such as aluminum body finned improve yo ur d irt-rtding skill KONIs) or gas-oil dampers (such as BilsteinsJ seems to be $100.110. t u ne your bod . Beg inner s t o pros. All makes This final modification will have the of bik es accepted - renta ls avai lab le. Tu it ion most noticeable effect on handling because, obviously, it's the most radical of those co nsidered . It will also probably require heavier spri ngs and higher visco sity fluid in the front forks. Both th e bolt-on brackets and t he relocated welded bracket will affect t he rake of the motorcycle frame. In 1320 Grand Ave. Suite 12, San Marcos, CA 92069 general , the tendency is for the bike to 714·744·2161 tum quicker when the front end is loaded up, as it usually should be in a tum. Whether or not this is a side effect you want, y o u 'll have to decide., Straddle tha t 'sickle. What actually happens with the siiock mounting position reloca ted is that the ......................................~ effective rake of the bike will change over a much wider range as weight transfer occurs from front to rear and vice vers a. There are probably even more changes taking place that simply riding it doesn 't immediately communic ate. There is a definite requirement to ride such modified : Flat Track Handlebars : frames with a heavier throttle hand, • • which in t um they see m to accep t, even : . $14.95 : demand. ' • • Somewhere in this collection of : H.J. Products : options, ranging in price fro m about : P.O. 1012225 · : $ 12 to about $220 is a step toward :: South Bend, Ind.46615 : m ore controlled , enjoyable handling ;; 219-289·3077 '.. : that will suit y ou. Total LTR suspension •••••••••••••••••••iaiAIlj for off-road bikes clearly isn 't fo r everybody wh o ri des a sc ooter and Greeves - Hodaka - Ossa so meti m es I wonder if it's for anybody Moto·X (:I Desert outside of the ranks of professional Nick Nicholson Motors o ff-r oad racers, At a cost of $70-100 per 11573 Vanowen, No. HoUywood inc h of increased rear axle travel, you've Racing since 1946. SeUing 2·suokes got to have some serious need for it . longer than anyone in U.S. And, like most needs, it m ay well be a pardy psyehological one: • • • • • • • • • • .. . • ·U IL.....:...._ ;",;.......:.:....:.... . Try ,us for your nesa dirE,b!k ~. _..J --=:....;.:;:;.._ Walk before you run (8) tr~;qva l~;;a : International Training Center IKEENER~ ~62 i CORKY ~ . · . 19·-

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