Cycle News - Archive Issues - 1970's

~ ,.. C'I QJ ..0 o .... u o An Italian Del Orto d08$ the carbin' chores. The air/oil fork modif"lC8tion is not stock. but is factory-recommended. (Left) A shower of dirt follows the big HoD number one where"er it goes. opmron that the metals and metallurgy are up to Swedish standards. The engine rests in a chromemoly double down-tube cradle frame with a box structure swingarm that is extremely rigid and well gusseted. The total weight of the package with gasoline came in on the official Cycle News spring scales at 212 pounds. Caressing the frame members is an abundance of plastic parts that . save weight and provide a place to put the traditional orange paint. How is it made? If you've been around the motocross scene for awhile then you know what it takes to make a competitive motorcycle. Even more than that you know what it takes to make an already competitive motorcycle rideable. In th e "money-is-no-object" world of dreams let's build a special one-off motocrosser and see how it works. The first thing we 11 need is a frame. No use messing around, let 's have Champ ion /Schwerma bu ild us a chromemoly frame, rectangular section swing arm, Timken tapered roller bearings in the fork stem , and heavy duty silent rubber /metal swing arm bushings. For forks we will get a set of 7-in ch travel Showa forks with optional gas conversion kit. Mounting the forks will be a beefy set of solid aluminum cast allo y triple clamps that are strong enough to avoid any of the flex that destroys the handling of the Japanese marques. At ' the rear end we are in a bind ; No two rear shocks, working independently of each other are going to work exactly the same; monoshock suspension works exactly the same, but puts a lot of weigh t up high, doesn't travel as far as dual shock suspension, and has the famous dead stick hop . It is ,truly a dilemma. We have seven inches up front, but can 't figure out how to go about responding to bumps in the rear - Why not put a set of gas forks on the rear swing arm, in a reverse of leading link suspension, to get seven inches of trailing link travel. Okay, it sounds logical so far , but now the dream bike decisions get a little tougher. To finish the rolling chassis we need wheels, rims, brakes, and tires. Let's just pick out the best front brakes we can start with , the proven conical front hub off of a Yamaha (manufactured by Sun) , nobody faults the front brake on a Yamaha. On the rear why don't we get a little tricky and mount an Airheart disc brake wi th H&H caliper to add a little pucker power. Now that is sanitary . The rims have got to be shoulderless alloy , and we might as well buy Sun rims and strap up a Yokahama 4.60 Super Digger on the rear and a 3.00 on the front . Hey, for a dreamland project the bike is beginning to take shape. Let 's roll our imagination out in the sun and finish bolting it together. Starting ' at the top let's begin w ith Malcolm Smith handlebars, Ou ry grips, Magura levers, Magura quarter tum throttle, Preston Petty fenders (oran ge, of course), Wescon cables , A.C .S. up and over expans ion chamber, Trapp silencer, Unifilter in an ABS plastic air box, Daido 5 25 Super chain, Whittaker plastic gas tank, Ossa foot pegs, number plates, hi-density foam seat and a Champion spark plug. For a journey into phantasy land we came away with a pretty nifty bike , utilizing some of the best accessory products available. As a matter of fact utilizing nothing but accessory products that were designed to replace production parts on other makes. Okay, let's bolt the engine in and see what it's like to ride the machine we built. Since we used the same parts to build our dream bike that Harley-Davidson used to build their MX-250 we might as well put in their engine. What is it like to ride? The bike is tall, it has to be when it has seven inches of travel at each end. Seat height is a King Kong like 36". The height makes the bike feel as though you are precariously perched on top of a monoshock, but the long 57 " wheelbase eases the tippy feeling once y ou get it on. It's best to pretend that you are Stackable or Weinert when you let the clutch out cause this Harley wants to travel at rapid rates of speed. Just hang your toe on the shift lever and hook a big hand full. There isn't a lot of compression , but because of the chrome bore it takes about a lap to warm things up, e specially with the light alloy cylinder keeping it cool. It 's a neat bike . Before you know it you are going faster th an you want to . The whole story behind this engine with its Bultaco like power (and innards) is to short shift it. Drive it hard through the mid-range and shift before y o u hit the top. It is more like riding a weak 400 than a 250. It has torque out the yang-yang, Gobs and bundles of get -me-to-the-ch urch-on time power. Stock it is one of the quickest 250's around. Not the fastest, although its top speed is higher than that of a YZ, but the quickest , The abundance of mid-range torque allows the rear wheel to drive the 4.60 knobby in and all the rider has to do is keep it going. R icky Pilgrim of San Marcos Harley-Davidson rode the test bike in the Support class at the Cyclerama National this summer and was on his wa y to a sure second place when his pipe broke. Pilgrim suggests that the be st way to get it around the track is to use -th e Kent' Howerton banzai clutch tactics in the comers. The bike has impressive drive out of the slow comers when you go in one gear higher than normal, feather the clutch and drop the hammer. Does the unusual suspension work? This is sort of a yes . and no proposition, in a surprising manner. The Kayaba Gas rear forks work well, with the power on and with the power off. The rear forks are stubby nitrogen-gas telescoping units similar to ones found on mini-bikes except three ti mes as structurally sound. We measured over five inches of travel just bouncing and pushing down on the bike while it was stationary. The b ike is fun, and the proof of the pudding is that y ou just don't notice the rear end at all. The front is a different matter. It works as good as any Japanese fork on the market, and because it is housed in sturdy triple clamps better than most. But it doesn't have that European feeling, best known as Maico-ism. The H-D company knows this and they suggest switching to alr-oil vsusp ensioa on the front. The recommended alterations are 185cc of 10 wt. Bel -Ray fork oil and approximately 37 Ibs, of inert gas or air (do not use oxygen). Bits and pieces You can't argue with the components on the machine. The levers, fenders, bars, and other accoutrements are high quality . The pipe broke during the testing, as did the ABS plastic on the edges of the airbox. Both of these areas need work. The carb flange connecting the Del Orto carb to the air box is a strange rectangular shape which defies hose clamps. Since the joint also defies silicone seal duct tape became the final answer. What is a trick b ike without duct tape? The decals on the tank peeled off. Shoddy , but it was one of t h e first bikes in the -co un try and will probably be fixed by the time the bike reaches fu ll production. The Trapp silencer fell off. A person could walk a motocross track every Monday and make a few bucks in scrap metal by collecting the silencers that fell off on Sunday. Ricky Pilgrim had trouble adjusting to the disc b rake set-up on the rear. It wasn't responsive enough for him. San Marcos Harley-Davidson, who supplied the bike and the technical info , bolted up a Yamaha rear hub with no problem. Conclusion The only conclusion that can be derived from this test is that the Harley-Davidson MX-250 is a new entry that because of the ridiculously small number of machines in the country, will not see wide appeal. When the Harley becomes available it will be the catalyst for a "Buy American" rage that could lead to coining a new phrase - "Win American." • 23

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