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/125889
Field test Yamaha YZ 80 mini-motocross By Dick Wright The rune to 16-year-ol d bikers of t oday don't know h ow lucky th ey are. T en years ago wh en you want ed to give your kid a little dirt bi ke so he could have som ething to ride wh en th e fam ily wen t to th e boondoc ks, you had about one choice . A Yam aha 80 st ree t bike, ligh ts, 17-inch wh eels. It was heavy an d big. Now there ar e a lot of good, dirt-ready bikes to ch oose fro m. The 80 YZ Yamaha is th e new versio n of the standard 80 Mini Enduro . It has all th e , tric k stuff , five-sp eed gea rbox, spe cia l fitt ed forks whi ch reall y do th e job, th e po rting has been ch anged to give it more RPMs an d it h as a new pipe to go with th e n ew p orting. T he co mp ression is up fro m 6.8 to 7.4 , and the carb is now a 20 m m Mikuni (las t yea r it was a 16mm Teik ei ). The price is abou t $499 and we hear they are hard to get. To do the bi ke j ustice, we got a top min i champ to do o ur te sti ng, Bobby Kline is I 4·years -ol d an d wei gh s 82 pounds, His wins include the 19 73 Min i Nati onals in th e I IOcc Modified class, 19 74 World Mini Grand Pri x a t Indi an Dunes plus the 1973 IIOcc Novice class at Hopetown and h as 75 trophies at ho me , so he knows what it 's all abo u t. We we nt out to Valley Cycle Park in Moorpark, California and he rode it for an hour. Bob 's no t much of a talker but here is what he said: D W How do you like it ? B W Neat ! I would like to h ave o ne, it han dles gre at. D W How does it co mpare with th e other mi nicyc1es? B K It wo uld blo w my 75 Ho nd a in the weeds. D W Then it's fast en ough to race as is? B K It's a st o ck bike but it's fast enough to race in th e modified class, I'd like to race it just as it is now. D W Is there anything that is bad about the bike? B K. Every time you go over big jumps the rear shock s go "clunk . " I m ad e a sh o rt run on t he bike at th e end of the da y, and fo und that it had surprising power . In fact , going up a hill in seco nd gear the front end came up so easy, it kinda surprised me. 14·year-old Bobby Kline, o ur guest tester, is just t he kind of rider the 1975 Yamaha YZSO w as redesigned for. It wei gh s abo ut 145 Ibs. and comes race-read y. The YZSO is a big improvement over the famil iar Mini Enduro. We don't know what they did to the suspension, but it sure works ! Th e bike can be taken o ut to th e races t he next day after you buy it , if yo u follo w a little co mm on sens e break-in progr am. Ride it aro und t he fla t fire ro ad s fo r a full tank of gas, m akin g sure you don 't lug it down or tu m it all the wa y on, and stop ab o u t every 10 minutes and let it cool. After the firs t tank of gas lo ok it over fo r loose nu ts and b olts. Rid e it ea sy a co uple of more tanks full. After a lo ng da y of co w trail ing and about four tanks of gas , get the bike race ready, check it all over . You can leave the oil inje ction on until you learn how to tune it . I. Check nuts (they were loose on the head of th e test bike). 2. Oil an d adjust th e chain. 3. Check transmission oil. 4. Tire pressure: 10 front-12 rear. 5. Check the spark plug, if it 's too clean, it's lean. It should be the color of choc olate, otherwise go to a b igger main jet or raise the needle, if it 's lean at the low end. The jetting on our test b ike was O.K. 6. Service the air cleaner. If your ri der is a first time beginner, don't let him get his "race face " on, just go for a clean finish and you'll be surprised how well he finishes up at the end of t h e day . It 's hard for parents no t to get over-enthusiastic when their child starts in this, but let the little racer set his own pace and let him build up his confidence and ability and you will have a great time togeth er , you ca n believe it! Specifications Engine and fra me number ... .. 492 -0001 01 Basic color (fuel tank) . . Compet iti on y ell ow Net Weight 138 Ibs. ENGI NE 2-stroke. 7-port. Si ngle, Reed V alve. A ir cooled 47 x 42mm Bore/Stroke 72c c (4.39 CID) 74 1 C.R . AU T OL U BE Minimum Pump St ro ke/ Col or Code 0 .30 - 0 .35mm (0 .012.014 ) Dark bl ue Main Jet No . 170 Needle Jet 0-0 4J13·3 Jet Needle/Clip Position 1.5 Cut Away 22 .5 Pilot Jet Air Jet 0 .5 Starter Jet No. 30 Air Screw (t urns ou t) . . .. . .• . ....• •.. 1:y,. A ir Filter . . • . " Wet Foam Rubb er DRI V E Primary ... ... .. .. .. . . . . .• . Hel ical Gear CA PAC IT IES Tra nsmis sio n Fuel Tank SOOcc (17 oz.) SA E 10W30 Oil 1.1 gals. U nlead ed or Regu lar Front Fo rks 110cc (3 .7 oz.) 10 .20 or 30 wt . Fork Oil Tires (size/ no minal pressure) 6 Front : . . • . . .. •. . .. . . . ... . 2.50 -16/ 10psi Rear •. .. ... •. . .. . •. . .. .. . . 3 .00·14psi ELECTR ICAL Poin t Gap/Spa r k Plug (type/ gap) 0 .3-0 .4m m/NG K B7HS or Champ ion L-81Y/0.5- 6mm Timing (adva nced ) (retarded) 1.8 ±. 0 .15mm BTDC/6