My motorcycles typically hold less than three quarts of oil, so using the same oil for everything isn't going to greatly increase the cost of changing the oil. The capacity of the wet clutch and transmission combined probably amounts to less than a quart.
Most of the bike engines I have taken apart do not have the gears submerged in an oil sump. There is usually a spray bar delivering jets of oil to gears and bearings and sometimes the crankshaft, which sprays oil like a wet dog shaking itself dry, is enough to keep the gears wet with oil. Lube that drips off the gears runs back into the engine oil sump to be picked up by the oil pump.
Actually I always wondered why the auto world didn’t just adopt m/c manual transmissions: the sequential shifting is much quicker and all-around better, IMO. Also, a clutch job on a bike is a non-event: drain the oil, remove clutch cover, remove clutch basket, replace plates! No “dropping,” “breaking,” or removing motor mounts.
The original Mini Cooper drive train layout allowed for clutch replacement similar to a motorcycle, @meanjoe. But their clutch was a dry single plate spicer type clutch. The Cooper setup was somewhat peculiar. Wet multi plate clutches do seem to have a great many advantages over the single dry plate and constant mesh transmissions would simplify shifting but pound for pound can they handle the torque load of conventional automotive manuals?
I agree. Having owned manual tansmission cars for decades, I understood that the fluid was a lubricant first with out combustion byproducts to deal with and not used as a hydraulic drive fluid. When used for purposes other then lubrication, they frequently have filters in my experieience. When used as a gear oil, they don’t. There are fewer chances for contaminants and the requirements in manual transmissions are usually just one dimensional; that is, provide lubrication. I have had manuals that used gear oil, motor oil and automatic transmission fluid. None had a filter. I have had friends who substituted auto transmission fluid for gear oil, just to make for easier winter shifting. One was an engineer and the other had a doctorate in physics and never felt the transmission lacked for lubrication. Quite the contrary. Both thought the lubrication was enhanced in cold weather. Being a lowly math teacher, I never questioned the wisdom of either guy. What is important for a manual transmission without a filter, is you check for metal filings that would indicate problems and if it had a magnetic plug, you keep it clean and functioning.
Hydrostatic transmissions are a type of manual transmission and do have a filter. But no automobiles have have them and they double as a hydraulic fluid both internally and else where. Now, having said all that, there maybe some hybrid manual transmission out there in the automotive world, that has a filter. That, being said just as a CYA.
@RodKnox: That Hayabusa is “wet clutch,” right? It puts out enough HP to put many “cages” to shame. Probably still fairly low on torque, relative to most autos…
Also, I think H-D’s V-Rod is a wet-clutch design. (Sorry, let me edit this to “is encapsulated in the block, shares motor oil with engine, and has no belt drive.”)
I’m not familiar with Harley’s beyond the late 80s and while I would feel somewhat certain they continue to use wet clutches on all models the toothed belt primary could throw me a curve, @meanjoe. A wet multi plate can handle a great deal more torque relative to diameter than a single or dual plate dry clutch and mounting the clutch at the transmission throws an increased torque load on the clutch.
That Hayabusa is "wet clutch," right? It puts out enough HP to put many "cages" to shame. Probably still fairly low on torque, relative to most autos...
The Suzuki GSX1300R aka Hayabusa has a wet clutch that runs in engine lube along with the transmission, 19 plates, 10 driving plates and 9 driven plates. The engine puts out about 102 lb-ft of torque at 7000 rpm and the factory claimed horsepower was 172.
As is common practice with motorcycle engine/transmission design, there is a primary gear reduction before the clutch, in the Hayabusa, this ratio is 1.596:1 or 52 teeth on the crankshaft and 83 teeth on the clutch, thus the clutch actually experiences 102 X 1.596 lb-ft of torque at full throttle and 7000 engine rpm.
Regarding that high torque loading, @BLE, do you suppose that the clutch and transmission and engine could stand up to repeatedly dropping the clutch at 7,000 rpm from a standing start?
Regarding that high torque loading, @BLE, do you suppose that the clutch and transmission and engine could stand up to repeatedly dropping the clutch at 7,000 rpm from a standing start?
Well, if you add a turbocharger to this engine, you probably should consider installing stiffer clutch springs. Seriously, there’s a reason that Suzuki GS series engines dominate motorcycle pro stock drag racing. It’s one of the most overbuilt motorcycle engines out there.
Enjoying a high performance car or motorcycle often involves pushing things to the limit and beyond. But everything does have limits. And exceeding them can be costly.
A few bits of additional data… There are motorcycle type dog-clutch transmissions for cars, race cars, that is. It is a standard upgrade on most racers, NASCAR, IMSA, Grand Am and the like. They use metallic or carbon multi-plate (2,3 or 4 plate) dry clutches. As for motorcycle wet clutches, most are multi-plate designs to handle the extra torque with very small diameter. Nearly every manual car has a single plate clutch for cost and noise (muliti-plate clutches rattle like heck).
Actually I always wondered why the auto world didn’t just adopt m/c manual transmissions: the sequential shifting is much quicker and all-around better, IMO. Also, a clutch job on a bike is a non-event: drain the oil, remove clutch cover, remove clutch basket, replace plates! No “dropping,” “breaking,” or removing motor mounts.
I don’t think the automobile crowd would tolerate the free lash that’s inherent in unsyncronized dog clutch transmissions plus the first time you nail the brakes in a panic stop and you find your car in sixth gear at zero miles per hour, you will sure wish you could just go straight to neutral and then first, without having to rock the car forwards and backwards so you can shift through all those gears to first. Dog clutch crashbox transmissions don’t like to shift unless the vehicle is in motion and stomping on the shifter in order to force it to shift is a good way to bend shift forks in the transmission.