Tested Dirt Bike Products - Yoshimura Exhaust, Enduro Seat/Billet Disk Gaurd, Kenda Tires - Experts on Dirtbikes at Dirt Rider Magazine

Products Tested
Yoshimura YZ250F Exhaust, Enduro Engineering KTM Seat and Billet Disk Guard, Kenda Southwick Tires and Silkolene RG2 GreaseENDURO ENGINEERING BILLET REAR DISC GUARD
In the world of rear disc guards, most are a very strong stamped or billet guard that is attached to the stock tabs on the swingarm. Those guards generally work pretty well, but the tabs are the weakest link. Some guards weld to the stock aluminum caliper mount, but some are unique. DeVol manufactures one the axle passes through, and Scotts makes a full billet guard that includes a new billet carrier. Now there is the Enduro billet disc guard. It bolts to the stock tabs but also has billet arms that run up along both sides of the caliper mount. EE claims its guard is 250 percent stronger than those that merely bolt to the swingarm tabs. We didn't test the strength on any rocks, but the unit looks good, mounts in a snap and seems strong. For $59.95, it appears to be priced right. Best of all, EE plans to manufacture them for other models soon.
ENDURO ENGINEERING: 517/393-2421; www.enduroeng.com
Rating 8.5AMERICAN KENDA SOUTHWICK K770
The Southwick K770 is designed for extreme mud and sand conditions and is available in most popular sizes. The tires feature tall, sharp knobs with a very open pattern that promises to clean well in mud and dig deep in sand at a bargain price-$33 to $72 depending on size.
We met renowned tire tester/designer Frank Stacy at our favorite sandy desert riding area. The place is fat with steep sand hills and trails that go up, down and across the slopes. Fresh rubber of an aggressive nature is key to a good time. Extreme sand treads, like the Bridgestone M26, Dunlop D773 and IRC M5B, are favorites of riders in the area. Compared with those tires, only the extreme M26 has knobs anywhere near as widely spaced as the Southwick. Stacy installed the Kenda tires, inflated them to 12 pounds and we hit the trails. We purposely looked for the deepest and softest sand we could find. The directional rear tire offers massive hook on sand hills and climbs like crazy with minimal wheelspin. It handles soft cambers pretty well, too. The front tire allows amazing stopping performance in soft dirt. We were able to steer and stop on soft trails we normally just sort of aim the bike. We did get into some harder conditions, and-like any extreme sand/mud-pattern front tire-the front slid fairly suddenly. The same was true of the rear, but to a lesser extent.
The wear on the Southwicks was minimal after the first day. On the second day, we climbed some sand hills with rock outcrops and rode some rocky areas and stream beds. Wear became more apparent, but the tires were still quite good. We went to Los Angeles County Raceway. LACR has two moto tracks, and both are composed of desert sand. They are usually intermediate terrain, but an overcast day ensured that moisture stayed in the track surface. Again the tires worked quite well considering they were too aggressive for the terrain. All riders commented on the straight-line acceleration qualities of the rear as well as the straight-line stopping grip of the front.
A third day in the desert after the rear knobs were well-rounded, and traction was still impressive. The front tire looked like new. We were blown away by the straight-line performance of both tires and with the value for the money. Performance leaned over was at or near the capabilities of other extreme tires. We felt they were a bit better in sand than in mud or snow, but still great tire values. Most of the time we would opt for the Kenda Millville rear, since it has a much wider range, but for sand, the Southwick is a clear winner.
The Southwick joins the renamed Millville intermediate-terrain and Carlsbad hard-terrain tires recently released by Kenda.
KENDA USA: 614/866-9803; www.kendausa.com
Rating rear in Sand 9.5, Rating Front in Sand 8,
Rating Rear in Mud 9, Rating Front in Mud 8ENDURO ENGINEERING KTM SEAT
One recurring theme in our KTM tests this year has been test riders bagging on the seats. The basic problem is the seat base. KTM dishes the underside of the SX-style seats to lighten them and improve airflow to the airbox. Where the rider sits most there is far less foam in the seat than it looks. For '03, even the E/XC four-strokes have the SX-style seat. Enduro Engineering didn't actually change the seat base, but it understood the demand for a better seat and sourced seats from SDG built to its specifications. We tried a standard-height seat with soft foam ($99.95), a tall (one inch taller than stock) with soft foam ($105.95) and a tall/firm ($105.95) model. Ken Faught raced his 525 E/XC both days at the GFI Elsinore GP, and by Sunday morning he was talking (we won't say sniveling) about butt-itis. So we swapped to the standard-height soft seat for Sunday. Karel Kramer opted for the tall/soft at Elsinore. It took a couple of laps for him to get accustomed to the grippy seat cover. Both felt that softer foam was a great benefit for the GP's conditions. As they put more time on the seats, though, Kramer thought the soft model was letting him feel too much of the seat base. He swapped again to the tall/firm seat. When new, the tall/firm seat was a bit of a stretch for a six-foot-one pilot, but with a little time, it broke in nicely.
The soft foam is really cushy after it breaks in, so if you have anything close to enough inseam, go for the tall/soft seat. Once broken in, it doesn't really hold you any higher than the standard seat does. The extra foam is nice to have when you're accelerating out of turns while seated. Shorter riders will have to opt for the standard-height soft seat. Riders approaching 200 pounds or more will probably get the best results from the firm foam.The EE seats are cheaper than the cost of a foam and cover, and you get the entire seat including brackets. You can literally slap it on in seconds. If your bike has any serious riding time on it, the EE seat allows it to feel fresh and new with none of the hassle of installing your own seat cover and new foam.
We're sold on the convenience and price and were most impressed with the comfort factor as well. Just be aware of your tastes in seat foam and order accordingly. If you think the stock seat is impersonating a brick, go with the soft foam. If you find the stocker just a wee bit uncompromising, go with the firm models. Once broken in, we'd say the EE firm seat is still softer than a stock seat.
ENDURO ENGINEERING: 517/393-2421; www.enduroeng.com
Rating Comfort 9, Rating Price 9.5, Rating Convenience 10YOSHIMURA 2003 YZ250F EXHAUST
With Yamaha's current monopoly on the 250 four-stroke market, going back to the drawing board to build a second-generation 250F before the other manufacturers could build any competition only added insult to injury. Much to our liking, the 2003 YZ250F rolled off the assembly line lighter, faster and easier to start. In the process of updating its little thumper, Yamaha gave the linear powerband better bottom and mid with less top-end and overrev. Although the change was not for the worse, we got on the horn with Yoshimura to order a $745 Tri-Oval titanium exhaust system to see if we couldn't squeeze some more top-end out of our well-ridden 250F.
Typical of Yosh, the titanium system bolted up with ease. As soon as the YZ-F fired up, we instantly noticed the pipe was louder than the already-mouthy 103-decibel stock unit. We immediately felt the added bite to match the bark on the track. The Yosh system retained the stock's great roll-on power down low but really enlivened the thumper's mid to top. The Tri-Oval's exceptional peak power eliminated the constant riding at the rev-limiter for our rev-happy test crew. Our testers also noted they didn't have to shift as much and could carry a lower gear due to the greater overrev.
Despite the 105-decibel (ouch!) sound reading, every one of our testers greatly preferred the Yoshimura unit to stock. The system did come with a spark arrestor; we pulled ours out since we were only interested in the Tri-Oval's motocross performance for this test. Plus the decibels could have earned us a ticket here in California (the limit at the time of the test was 101, it will be 96 by the time you read this).
YOSHIMURA R&D;: 909/628-4722; www.yoshimura-rd.com
Rating 9.5SILKOLENE PRO RG2 SYNTHETIC GREASE
The last time we went truly gaga over grease was, well, never-until now. Even now, it isn't the chemical compound or the actual quality of the lube that has us excited. We have no doubt Pro RG2 is a great chassis lube with all the weather protection Silkolene claims for its lithium-based grease. It has a nice, clear red color that looks efficient, and it feels slippery yet has the viscosity needed to stay where it is put.
The problem with grease is that it is always greasy. That's good for bearing but icky sticky for hands and clothes. We've been able to get great use out of our can of Pro RG2, and we haven't actually had to touch it or get any on our hands. How sweet is that? Silkolene packages Pro RG2 in a pressurized can-not an aerosol can that sprays a light white grease, but a Cheez Whiz-type can with a semiflexible nozzle. You turn the can upside-down, push the nozzle sideways and it dispenses a perfect bead of grease on bearings or air filter edges with no mess and no fuss. Of course, if you really have to pack in the grease for a linkage or wheel bearing, you will need to get those fingers in there, but for the routine maintenance a motorcycle requires, you'll never need to touch it. When you put Cheez Whiz on a cracker, you don't smear it around with your finger, right? Silkolene is distributed by Tucker Rocky, so you can get Pro RG2 at any dealer for around $8. Our staff garage houses several cans.
SILKOLENE: 800/214-race (7223); www.silkolenestore.com; www.silkoleneusa.com
Rating 9.5