Some models of big motorcycles are equipped with hydraulic clutches because the clutch can be disengaged with a light lever operation. This may sound like a maintenance-free solution compared to mechanical clutches, which require regular wire cleaning and lubrication, but the brake fluid, the hydraulic fluid, needs to be changed every two years. If you put it off, the engine side release may fail.
Hydraulic clutches require the same regular maintenance as hydraulic disc brakes
The V-MAX was produced for 22 years from its debut in 1985 and was loved by many riders for its one-of-a-kind style and character, and the popularity of the first generation never waned, even after a fully redesigned version was introduced in 2008.
Even the last model is more than 10 years old, and the condition of used motorcycles varies, so riders who are thinking of buying one should assume maintenance of the whole body. As for hydraulic clutches, it seems that there are many vehicles that cannot disengage until the lever almost touches the grip due to lack of maintenance.
There are two types of clutches to be used for gear shifting, mechanical clutch operated by wire and hydraulic clutch using hydraulic power. Both are mainly used according to the tension of the clutch spring, and hydraulic clutches are often used for large vehicles.
It is effective to strengthen the tension of the clutch spring to prevent the clutch from slipping in large vehicles with large engine power and torque, and by using Pascal's theorem, it has the advantage to lighten the clutch operability which becomes heavy with strong spring. Even for a mechanical clutch, it is possible to reduce strong spring with light force by balancing the fulcrum, force point, and action point of the clutch release arm. However, in that case, it is necessary to take a large stroke, and there is a limit within the range of common sense lever stroke. On the other hand, the hydraulic clutch can generate large force with limited lever stroke by the piston area ratio of master and clutch release, similar to the relationship between the master cylinder and caliper piston of the disc brake.
Such hydraulic clutches have the feature of stable operability compared to the mechanical type over a long period of time. Due to the long distance of the mechanical wire, poor lubrication of the contact area between the outer and inner wires directly leads to the deterioration of clutch lever operability. For this reason, many riders are particular about the subtle feeling of half-clutch connection and frequently lubricate the wires.
On the other hand, the hydraulic clutch does not need to worry about the extension and lubrication of the wire, and always provides a stable operation feeling. The relationship is similar to that of a hydraulic disc brake, where the piston automatically extends as the pads wear, and braking is always done with the same feeling, as opposed to a mechanical drum brake, where the brake lever play increases as the brake shoes wear.
This does not mean that hydraulic clutches are maintenance-free. The hydraulic fluid used in the hydraulic clutch is the same brake fluid used in the disc brake, and while it does not boil easily even when exposed to high temperatures around the engine, it is also highly hygroscopic. For this reason, it is specified in the service manual as a regular replacement part every two years. However, since there are no parts that wear out like disc brake pads (clutch plates also wear out, but their life span is generally longer than that of brake pads), they are often overlooked with no maintenance.
The clutch release of V-MAX is directly attached to the crankcase and hidden behind the flywheel cover and the middle drive cover, so it is hard to notice. Since the touch of the lever is uncomfortable and the disengagement is not good, I removed the hose leading to the clutch release and inserted a hexagonal wrench through the gap to remove the release body.
- Point 1 - The hydraulic clutch is an effective mechanism to operate a heavy clutch with light force.
- Point 2 - Hydraulic clutch fluid needs to be changed periodically once every two years as well as brake fluid.
The clutch release may be affected by heat depending on its mounting position.
The specification differs from year to year, but in this relatively early model (1986), the part that looks like the key part of the long nut is the passage for the clutch fluid. The passage of the bleeder plug is also long and protrudes, and this shape shows that it is installed in the deep part of the V type engine.
When air is supplied from the long nut side with an air compressor, the piston is pulled out from the front side of the release. There are some oozing marks, but no clear leakage. Unlike the external impression, the inside of the release is filled with deteriorated fluid that emits a strange smell and paste-like foreign matter.
The V-MAX is OEM parts set up and cannot be purchased as a single-piston, but as a set with the release body. Since the seal kit is set up as a single item, it is important to check the piston for scratches and damage. Remove the seals and clean them with parts cleaner.
It is the clutch release that pushes the pushrod that makes the gap between the clutch disc and the friction disc by the clutch lever operation. In contrast to the clutch located on the right side in the direction of travel, the clutch release, which pushes the push rod through the crankcase, is installed on the left side of the engine. The more specific mounting location is either the drive sprocket cover or the crankcase direct on most models.
In both cases, since it is located on the left side of the vehicle, it is easily affected by moisture when it is stored outdoors on a side stand without a vehicle cover. In addition, if the release is mounted directly on the crankcase, it is necessary to consider the effect of heat from the engine. Of course, there is nothing to worry about if the maintenance has been carried out regularly, but if the motorcycle has been bought second hand with no known maintenance history, or if the motorcycle has been owned for a long time but the fluid has never been changed, the deterioration may have progressed.
The symptom of a clutch release that does not engage when the clutch lever is depressed is terminal and is difficult to occur on a motorcycle that is ridden on a daily basis. However, fluid oozing or leaking from the release does not necessarily occur only on the immobile motorcycles. There have been cases where a stain on the bottom of the engine was thought to be oil but turned out to be clutch fluid.
When fluid leaks from the release, it is fed through the master cylinder, which reduces the amount of fluid in the reservoir tank and lowers the fluid level in the inspection window. If you miss this and continue to use the motorcycle and the tank becomes empty, air will get caught in the hose and the clutch will not disengage. To avoid such a problem, it is essential to check the fluid level in the reservoir tank.
- Point 1 - Clutch fluid deteriorates by absorbing moisture in the air and being affected by heat.
- Point 2 - If fluid leaks from the clutch hose or release and the master cylinder is empty, the clutch cannot be operated due to air bite.
The Yamaha V-MAX is a long-selling model that is often poorly maintained.
When the fluid inside the release was cleaned out with parts cleaner, traces of deteriorated fluid remained and there were bumps where a fingernail could get caught. Since the material is aluminum, there are no signs of corrosion, but it is no wonder that the pistons do not operate smoothly and affect the clutch operation.
The cylinder honing tool is used to polish the inside of the cylinder to remove dirt. This tool is available in several sizes according to the cylinder's inner diameter, and the roughness of the grinding wheel on the tip can also be selected.
After adjusting the tension applied to the three legs with the nut on the shaft and inserting it inside the release, turn and grind it with an electric drill while spraying it with lubrication spray. Instead of turning in the same position, stroke up and down inside the cylinder to remove dirt. It is important to select a fine grindstone and not to over tension the grindstone because the inside diameter must not be enlarged.
There was still a little dirt on the surface, but I was able to scrape off the hard deposits where the clutch fluid had turned. I cleaned off the rest with a metal polishing compound.
The Yamaha V-MAX is one of the most common hydraulic clutch-related problems found on the Internet. This may be because it is a long seller, has a large number of units on the used motorcycle market, and the clutch release is mounted directly on the crankcase. Riders who are not interested in motorcycle mechanisms may not be aware of the existence of the clutch release itself, as it is hidden behind the middle drive gear cover of the shaft drive (or drive sprocket cover for chain drive).
In such a situation, the condition of clutch release deteriorates due to heat and moisture of the engine and deterioration of clutch fluid. Specifically, deteriorated fluid becomes gel or sludge and accumulates inside the release, or fluid that seeps outside the release crystallizes and prevents smooth movement of the piston.
In addition, dirty fluid may adhere to the piston seal surface and damage the seal itself as it strokes, thereby causing fluid seepage and leakage to progress. The clutch release is the opposite of the brake caliper, with the seal mounted on the piston side. The dust boot covers the gap between the piston and the release, but if the fluid leak that has developed inside of it reaches its limit, it will flow out of the release and cause fluid to stain under the engine.
When the inside of the release is dirty like V-MAX introduced here, it is reasonable to think that the inside of the master cylinder and clutch hose is also dirty. First of all, it is the first step to keep the clutch in good condition to change the clutch fluid every two years even if there is no discomfort in operation, but if the operation feeling becomes worse or fluid leakage is confirmed, it is necessary to overhaul the clutch release.
The seal set that attaches to the piston should be sprayed with a rubber seal assembly compound to ensure a good fit. Clutch fluid = Brake fluid may be applied, but handle with care not to get it on painted surfaces or on the outside of the release body.
While inserting the piston into the release body, put the dust booth set on the tip over the release body, and apply grease to the contact surface with the pushrod. If there are any fluid oozes left on the engine side, clean it up.
Push the assembled release through the narrow gap and fix it with two bolts. After the clutch hose is reassembled, the fluid is injected from the master cylinder side, but it is important to clean the master cylinder and hoses separately before reassembling because if the inside of the hoses is dirty with deteriorated fluid, the dirt will flow back into the release.
- Point 1 - A clutch that has not had the fluid changed for a long period of time may have various problems.
- Point 2 - If there is any discomfort in the operation of the clutch lever, it may be necessary to overhaul the master cylinder in addition to the release.
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See Accessories for YAMAHA VMAX 1200
