Cycle News - Archive Issues - 1980's

• IS • rrt trac o 00 '- Or, how to make a TT bike from your CR250R Honda motocrosser 0') By Jerry Greer Photos by Dale Brown and Dan Mahony emember TT scrambles? 'inhey' remember Tile 5uperbikers ra last year? It pitted the country's (iirt trackers against the top road racers ana motocross- 14 For myself, SRO tracks and mIf iriil up my week· ends and I enjo,y Iy. The price of race entry fees is low, the competition is interesting, the fast sliding is a ball, and the up-\teep'on my Champion din track framed Yamaha 400 is low. Compared to a I1lOtOCJ'OIISeI getting a comparable number of race dates per month, the upkeep dollars are downright negligible. No broken frames, no new shocks , no new sprockets, no new chains, fewer tires , no new rims , hubs and spokes . In short, low bucks to go TT racing. I like that. I also liked the idea of possibly being competitive on a modified motocrosser among a bunch of dirt track bikes. And, if it didn't work out, so what? People forget. (Except for the time my '35 Indian kick-starter pedal tagged me in the forehead and left the neatest grade-five bolt head imprint. Nobody lets me forget thatl) But I was sure it would work, at least well enough fo sportsman scrambles where track con ditions vary considerably, from smooth to pretty bumpy. ' . ~ __ From where I sat, it seemed .~ mcXlifying a motocrosser similarly to those of the Superbiken' woUl be easy '7 enough, and be aff~IY.i,~. I man the project by c1iOOlling a '79f HoDda CR!50Rmotocrosserto modify. 1'beTe are 1'Ienty around. I then listed all of the handling and engine performance traits of the MX bike that were undesirable from a fast, smooth track racing standpoint, and then listed all the traits of a typical dirt track framed special that were desirable, From the two lists, I then culled out those desirable traits whiCh could only be achieved with lots of money and machine shop resources, or those which were only de sirable, but not absolutely essential to the success of the vehicle. For example, on one hand , the stock 29 degree rake and 4.7 inches of trail, were undesirable from a sliding standpoint, but I couldn't do much about it inexpc:nsively,. So, I decided to see if u1d sUffer too much the more typical 26·27 3.5 inch mill or contrack framed TT bikes. her hand, the Motocrosser needed t iowered in a bad way. '"Ehe center of ~vi~ was approximatel! 30'l inches above the ground witli the seated in the foreward mounted position, as compared to a TT bike', lower average 22 to 24 inches above ground CG. Since I was able to easily lower the bike and significandy reduce the problem of high CG, I did so. Doing so also diminished the inherent high altitude problem with long-travel suspension motocrossers . Lowering the bike eliminated the air gap between the rider's feet and the ground. The necessity of this move is evident if you've ever pitched the bike into a corner, got it down as far as you thought prudent, and then stuck your foot down - only to find it still six inches above ground. 1t11 make you believe in being closer to the ground on a smootli, slidy track. Anyway, that was the general sol'ting out process I used to develop the performance envelop for the motocross bike-turnedTTbike. Before ¥OIl go any further, you want to know if the project bike woded. Right? Yes, it worked. Eddie Lawson ' umped on it at Sad.d1eback and daz zled: everybody who- was out 'Saturday afternoon practicing on the short tl'aclr.. ;The daizlees included a~way bike rider wlio trieCt, but couldn't keep up, an assorted nuJnher of motocross riders (em everything from an identical, but unmodified Honda CR!50R, to a poor soul on a clapped-out Ossa exercising his death wish. Tbe track stunk - big potholes on the number two corner, which would have made the track unridable on a conventional TT bike . And the rest of the track was so hard, dry and snotty that the motocrossers could barely, and I mean barely, negotiate the track without doing ground loops , wowees, and gymnastic tricks normally associated with the Olympic Games. Lawson thought the bike did great , having started out as a motocrosser. All he asked for was a steering damper. naer , Next, Ross Klatt, a hot Pro Novice in the din track ranks this year, blazed around on it. He liked it too, but didn't love it . Fortunately, I kept lap times on both him and Lawson. Lawson, a dirt track Expen, and recent winner of this year's Daytona Lightweight road race , was just a quiver faster than Klatt. After I told Klatt about the lap times, he liked the bike better. He also admitted the track was so bad that if he were required to go and cut some laps on his 250cc dirt track framed bike , he's probably be enjoying the comfort of a semi-private room at Saddleback Community HosphaI. As a later backup test, I had Pete Hames, one of the hottest 250cc Sportsman TT and short track riders in the nation ride the bike at Indian Dunes. He, like Klatt, has the latest trick TT bike which obviously handles different1y. He didn't appear comfortable on the Honda, but he did go fasd He then tried his own bike out on the small track, but didn't visibly go much faster. The Honda certainly was usable and competitive. The last test was my own . I rode the modified motocrosser in an Open Expert TT race at Corona Raceway, giving away a 250cc advantage to the bigger 500cc thumpers and such. The two previous weeks, I had finished third on my 400 Yamaha in a Champion dirt track frame. This week, I fmished . ... . yq>, third again! And I wasn't nearly :is tired. ; On a scale of one to 10, I'd give ita " nine and a half on cobby TT tracks and a seven on smooth TT tracks. In standard motocross trim, it would get a big six on cobby tracks and a four on smooth tracks. Let's get into the nuts and bolts of how to make your Honda motocrosser into a TT bike . A separate table lists the pieces necessary to make this conversion. Since the Honda puts out good, competitive. horsepower, and is light (216 Ibs. dry), there wasn't too much to take off. and ( saw no need to make the engine less reliable and more expensive by hopping it up. About all I could scavenge off was the front fender, kickstand, front number plate and the rim locks.

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