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Bike Mods With Guy Cooper

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This article was originally featured in the August 2017 print edition of Dirt Rider

Rear Shock

I had several works shocks. Theoretically they were all the same, but there was one that was better than the others. The Showa guys and my mechanic, Marshall Plumb, would swear up and down that I couldn’t tell the difference. So Marshall would send me out on the other shock and I’d come right back in going, “This isn’t the right shock.” I knew. It was weird. By all definition it should have been the same, but I just liked one in particular better. So it became—coming down to the wire—that shock would get shipped out, overhauled, and airfreighted back every week to get it right. They thought it was in my head. Marshall kept thinking there’s no way I’m going to be able to tell the difference because it should have the same feel. That was the only thing that mentally really bothered me.

Tires

I ran a Dunlop 695 rear and the K490 front 99 percent of the time. At Southwick they wanted me to run the 990s, and several times I’d run a 490 in the front because the 990 would stick, but it would, like, high-side me, so I kind of liked my 490.

We did tons and tons of testing prior to the nationals. You know you had the weeks off after supercross into the outdoor nationals, where we put in so much time. Then the first two or three months of the nationals, the way [team manager] Ron Heben set it up was there were seven factory riders, five in the 125, two in the 250. Everyone got the same equipment until the first round. After the first round the parts that were “onesies,” where they just had one of a special part, the guy in the top of the points would get it. So in Supercross I never got to test anything other than what I had at the start of the year because it went to LaRocco or Larry Ward. In the outdoors I got the chance to get all the one-off stuff.

Exhaust

So we were talking about one-off parts. In the outdoor season, there was this exhaust pipe that I ended up with—the Japanese didn’t like it but, to me, I liked right where the meat of the power was. It just felt so good in one area. The Japanese kept trying to convince me to try this other pipe. Every time Marshall—we’d test it probably 10 different times and we always went back to this one; they called it the 1062. The pipe was a one-off factory with “106.2” stamped on it. The Japanese tried to get me to run a different pipe they said had more torque, but I liked the feel of the power. Seemed easy to tell you were in the good range. I rode the bike wide open, so on this pipe the meat of the power was like three-quarters to wide open. It suffered off the bottom, but I didn’t ride there.

So the stock gearbox was a wide-ratio one, compared to the works gearbox. They had a close ratio, which finally reached production in ’93 and went into the ’94, ’95 RM125s. I didn’t like the close ratio; it was better for SX. The other guys could out-drag me down the straightaway if we did drag racing. But on the track where you couldn’t always get that shift, I could carry it through the ruts farther. With the wide-ratio gearbox and the pipe, it was great—we did our homework. Once I got this setup down I didn’t alter off of it for the last five or six races.

Steering Offset

We played with a little bit of offset at the very beginning, but the bike actually handled pretty good the way it was.

Suspension

Coming from my last couple of years working with Roger DeCoster at Honda, I always fought him. I wanted a softer bike. He wanted it stiffer. So my Suzuki was stiffer than my Hondas, but I knew I needed to go stiffer. And if you remember in ’88 the first of the works upside-down forks, those things were unbelievably harsh. That’s why George Holland didn’t run the upside-down. He ran conventional forks and I ran the upside-down forks. So I got used to a little bit of a harsh feel. But what that helped me with was when you would hit the berm because you felt everything in the track—you knew you were stuck in the berm. The upside-down works Honda forks, it would take me 3 or 4 or 5 feet through into the rut to realize that I had gotten there. So there was a benefit of having it not so plush.

Besides the shock and pipe, one part I remember, I think I had an M shifter, which the splines are halfway between what a production shifter is. So this way it was just a little bit…It’s a half of a click. So I would set it a little bit higher. I ride off the back of the bike. I needed to get my foot under the shifter. But a full click of a stock shifter was too much.

The factory bike had the Nissin brakes, and I griped every week because if it didn’t get rebuilt—the small piston, it would hang up. This is something I’d do almost every morning of a race. I’d sit on the bike and slowly pull the brake lever in. What was happening is, with that small piston, it would get bound up. So if you barely held it, like you were going into a sweeper, it would bind up to where you could keep pulling and it wasn’t pushing the plunger. All of a sudden it would give and then it would lock your front end up. A stock one didn’t have as precise brakes, so it wouldn’t have that binding to where it would jack with you. So I’d sit there and I’d make sure he rebuilt the master cylinder each week. If it wasn’t greased, you could definitely tell that… The brakes were really good though. And I’m a stab-and-go kinda rider on the rear, so more aggressive rear is better, and I’d skid the rear in and take off.