It's been a while since I've had the chance to ride my NSR250R, but the SP and SE road-going racer models came with a "dry clutch" as standard equipment in some years. Here, let's take a look at the "dry clutch" that is in contact with the outside air, unlike the fully packaged wet clutch, for inspection and cleaning.
Image in advance of work by looking at genuine materials
Before this maintenance, we prepared the service manual and parts list for the model. The service manual contains technical data and cautions for disassembly and assembly. The parts list is used to check the assembly of the parts and the part numbers of consumable parts such as gaskets. Of course, if you find any damage to the parts, you can pick up the necessary parts from the parts list and order them. At Webike, you can order genuine parts for both Japanese and foreign motorcycles.
A "dry clutch" is exactly what it sounds like.
While most motorcycles use a wet clutch system (clutch system immersed in engine oil), the NSR250R's SP (Sports Production) model, a serious racer replica, used a dry clutch (the first generation SP model in 1988 had a wet clutch). This was to improve the ease of maintenance and to increase the cooling speed of the clutch, which tends to overheat when it gets hot. After removing the cover, grip the clutch lever and check if the outermost control plate rotates smoothly with your fingertips Let's check it out. If the clutch is stuck, it shouldn't freak out. This time it turned smoothly.
Remove the clutch spring fixing bolt.
The control plate is actuated by 5 bolts & clutch springs. Although it varies from model to model, clutches for motorcycles are generally 4 to 6 spring specification. This is the same for both wet and dry type.
Imagine an easy-to-use pick tool!
The multi-disc clutch specification, whether wet or dry, is a feature for motorcycles. The clutch friction disc and steel clutch plate are removed, and it is very convenient to have an easy-to-use pick tool. A pick tool with a magnetic rod is useful for the steel plate, and two thin pick tools are useful for the friction disc. The recommended homemade tool for clutch maintenance is the spokes of the spoked wheel that are no longer needed. By cutting off the nail heads of the bent spokes with a grinder, you can make your own L-shaped pick tool. The removed discs and plates can be hung on the step in the same order as they were assembled for easy inspection during restoration.
It's a dry clutch.
Pull out the end piece of the pushrod that allows the clutch to disengage. This part incorporates a cup-type oil seal (some models have a simple O-ring). (Some models simply have an O-ring.) This is designed to prevent gear oil from entering the dry clutch. If this seal is damaged and corroded, it may become sticky and clutch disconnection may not go smoothly. This time, it worked smoothly. There were no oil leaks or seepage. After removing the end piece of the push rod, remove the tightening nut of the clutch hub (also called clutch center) with an impact wrench.
Check dents on clutch outer.
Let's visually check the area where the forged aluminum clutch outer groove and the friction disc convexity meet. In many cases, the clutch outer groove of the motorcycle that has been repeatedly used for rapid start and rapid acceleration has become quite uneven. If it is uneven, smooth movement cannot be obtained and smoothness cannot be obtained when clutch is disengaged. Be sure to inspect it.
Focus on large oil seals!
The clutch outer can be removed by removing the clutch hub and removing the bolt that tightens the clutch outer. Hiding behind the clutch outer is the large oil seal. If there is damage to this oil seal lip, the clutch interior is dirty with gear oil. In this case, it was dry and covered with dust from the friction disc. Before restoration, it is recommended to clean up the clutch chamber thoroughly to avoid damaging the oil seal.
- Point 1・If you own a dry model, you should disassemble it periodically to check and clean the inside to maintain the condition.
- Point 2・If you have a feeling to own it for many years, you should buy spare parts for consumable oil seals and gaskets. It's too late after the sale is discontinued.!!
It is the wet clutch system that interrupts the driving force in the sealed clutch cover (lubricated by gear oil). On the other hand, unlike the wet clutch system, the wet clutch system operates in contact with the outside air. When the clutch is depressed, the sound of clattering can be heard, which is characteristic of the dry clutch. Although the wet clutch also has mechanical noise, the noise is not loud due to the constant lubrication with gear oil and the sealed clutch cover. Let's try to disassemble and maintain the dry clutch to take advantage of its easy maintenance.
This is a sports production model equipped with a dry clutch as it is a base motorcycle for racing and a homologation model. In order to achieve the best performance, daily inspection and maintenance is extremely important. For racing use, disassembly and maintenance will be done after practice rides and before races, but for everyday street use, the overwhelming majority of users are likely to leave the motorcycle unattended. It is important to understand the character of the model and to remember that without regular maintenance, it will not perform at its full potential. Not only that, but the life of important parts may also be shortened, so be even more careful.
What should be noted when disassembling is to visually check the condition of the concave groove of the clutch outer and the convex/concave groove of the clutch hub. In the case of wet clutch, lubrication by gear oil and oil film works to mitigate interference, so clearly "clear dents" are left on the dry clutch specification when comparing engine parts that have to ride the same distance. If you want to keep your beloved motorcycle for a long time, you should not only secure spare parts of clutch friction disc, clutch plate, and clutch spring but also spare parts of clutch hub and clutch outer.
Also, when you remove the clutch outer, you should check the condition of the large oil seal behind it. It is a part that does not leak oil easily, but if gear oil enters into the dry clutch chamber, the clutch disc will slip immediately. If the area around the oil seal is damp and black with oil stains, it will be necessary to replace the oil seal. Therefore, if you want to enjoy your motorcycle for a long time, you should keep a spare oil seal.
