Suzuki RM-Z450 Motorsports - Dirt Rider Magazine

Well, I can say it has been a good ride. The yellow bike and I have bonded, as with any good relationship between man and machine. Except I wasn't very nice to the RM-Z or my wallet in the process. It survived some supercross, helped me train up for the Nationals, became first a practice bike and then, even worse, an off-road practice bike as I've lately been getting into WORCS racing.There were no problems in the beginning. I did the usual oil and filter changes and checked the spokes and the fuel, oil and coolant levels every time I rode. But I neglected to check the valves. Yet there still were no problems. At more than 40 hard hours, I decided that I'd better not push my luck. I did a top end and a valve job. Being a rookie mechanic, I made a fatal cam-timing mistake-and it was costly.Problem number two happened 80 hours into the bike's life. The bottom end was letting go. The bike was still running, and I should have known to stop riding it. I now know that metal shavings from the bottom end were carried up into the head, wearing everything out. This mistake meant I had to replace the whole top end as well as the bottom end (minus the transmission). I learned another lesson about four-strokes the hard way-through my checkbook.In October the bike was reassembled with the help of race mechanic Corey Shea. I used the RM-Z to keep in shape and try to get ready for the WORC racing series. I went to my local practice tracks and on quite a few trail rides. The hours kept racking up on the bike with no accompanying problems-just basic wear and tear, at a pro level. At about the 110th hour, some extra noise came from the chain area. The chain had worn right through the chain block and ruined the chain guide. Maybe I need to look over my bikes a little more closely? During the 122nd hour of torture to the bike, it just died-while landing off a jump. I kicked the bike for a while and heard some noise coming from the ignition side of the motor. The bolts that hold the magneto to the ignition cover had backed out, and when one broke off, the bike stopped running. I know they were Loctite-ened in, but maybe some oil had been left on the bolts. In hindsight, the bolts should have been replaced. I had another costly repair on my hands, including the ignition cover and magneto assembly.Late in the bike's pounding, I found that my subframe was broken just above the lower muffler mount. Over time I've had to replace the clutch, chain, sprockets, upper chain guide, rear brake pads and rear rotor (which had a small crack in it). I am a brake dragger, so I'm sure that led to the cracked rotor. I freshened up the looks one more time with a set of Factory Effex graphics.I rode the bike for 19 more hours without incident, then finally retired the Suzuki to the studio for the final teardown and photos. With the help of Jimmy Lewis, I tore through the motor, inspecting every part. We noticed the moderate wear on certain parts and the minimal wear to other components. I hadn't seen any metal in the sidecover oil filter from the ignition bolts coming loose. Well, when the cases came apart, we saw that the filter screens had done their job! We found where the missing particles had ended up. It is a shame you have to split the cases on this bike to get to them, but on the 2007 RM-Z450 you have easier access. The only other issue was the small end of the rod had some small galling inside and on the piston pin. I've learned that at my riding level and speed I need to be inspecting the top end of a 450 every 40 hours. This one might have been on its last leg. And that metal from the ignition didn't help.I've put a lot of good hours on this RM-Z450. One hundred forty-one, to be exact. I can honestly say that I was impressed with the bike-and surprised when I finally saw how expensive it is to be a struggling privateer, just in terms of bike parts! The first problem at 64 hours was my fault. The bottom end snafu at 84 hours is something that was going to happen on any bike; I just rode it too long while it was making noise. And the magneto bolts backing could have been prevented if I had put in new bolts. Truthfully, all I ever did to the bike was put in gas and change the oil and air filters. I never checked the valves, and the bike always started on the first or second kick. I'm going to miss this machine, but it won't miss me!Running Tally
Hours on Bike: 141(55 since last update)
Modifications: $2647.53
Factory Effex dual-grip seat cover: $59.95
Factory Effex Signature Series graphics kit: $109.95
Factory Effex Signature Series matching backgrounds: $59.95
Maintenance and Repairs: $7345.87 (not including tires)
13 qt Torco T-4MXR: $8.75 each 4 oil filters: $8.95 each
Tag Metals rear sprocket, 50T: $59.95
Tag Metals front sprocket, 14T: $29.95
Oury grips: $7.95
2 bolts: $2.98
Magneto cover: $129.91
Magneto gasket: $7.21
Clutch plates, metal and fiber: $140.50
6 clutch springs: $19.38
Magneto assembly: $354.29
Subframe: $367.67
Chain buffer: $32.13
Chain guide: $40.72
Chain plate: $29.68
Rear disc: $100.84
Rear brake pad: $28
5 sets Bridgestone front 401A ($92.97 each) and rear 402A ($116.42 each) tires*
*Mostly used takeoffs from race bike.