MHarryE
Elite Member
- Joined
- Feb 15, 2009
- Messages
- 2,980
- Location
- Northeastern Minnesota
- Tractor
- Kubota M7-171, M5-111, SVL75-2, RTV900XT & GR2120; CaseIH 1680 combine
Here is another explanation of the phenomena - this explanation pertaining to motorcycles but the same thing and probably easier to understand example with the cold oil equivalent to sticky honey on a slice of bread and trying to slide it.
I can't explain why it should move if the gears are in neutral but then again I don't have a cross section of the transmission. Yes, I have had transmissions transmit some power while in neutral but in the cases I can recall due to excessive heat and not excessive cold.
When I get home it should be below zero (F) and I will try my M135GX. Different transmission but a lot more wet clutch packs involved. It's also time I tested the block heater.
Q. Why does the Rear Wheel Turn when the bike is cold and I start in Gear, with the Clutch Pulled in.? Why is it difficult to start.?
A. The F650 has what is called a "Wet" Clutch.
Unlike many cars, where the clutch is separated from the Engine and sump, many bikes have a clutch which runs in an oil bath, the same oil that lubricates the rest of your engine.. You might ask how this works when oil is pretty slippery stuff, but if there are enough plates (The F has 7), strong enough springs there will be enough friction. Plus Oil is a very viscous liquid, so some of the transfer of the engine power across the plates is done though the oil.
A wet clutch has multiple plates running in the engine's motor oil, like the F650 engine. A dry clutch runs in its own housing and consists of one or two plates. Think BMW boxers and Moto Guzzis and most cars and trucks. They both work fine, if properly designed. A wet clutch is typically more compact and will usually engage more progressively, however as it wears, it tends to foul the engine oil with clutch material. Wet clutches are also quieter than dry clutches (think Ducati). Richard #230
Dry clutches last longer, too in most cases. Some are equally quiet, as the BMW dry clutches are noise free. Ducati has the market for noisy clutches! Don't even have to see the bike coming to know what it is. Changing a wet clutch pack is almost always easier than dry bike clutches. More labor involved in most cases, for dry ones. Costs? Wet clutch packs are much cheaper as well, when comparing the BMW clutch assemblies. Feel? Not much difference, these days, but there was a day when the early BMW dry clutches on the early boxers were snatchy! Randy748/Calif
Oil itself, until it breaks down over time or with wear, has a fairly high viscosity for a fluid. Ever dropped a piece of toast with honey on the floor and tried to pick it up sliding it across the floor a bit. Difficult isn't it.? In the same way the very small amount of oil between the plates is the same. Viscosity is temperature-related. When it is cold, oil is "thicker", i.e. has a higher viscosity.
The Clutch comprises a "Basket" Part#1 (External) & Part#2 Internal, Several Friction Disks Part #10, Several Steel Disks Part #11, and a Pressure Plate #12, which jams the whole sandwich together using the springs, 6x Part #1.
The difference between Neutral and in-gear with the Clutch in, is that in Neutral the Clutch Basket, which houses the Clutch Friction Plates and the Smooth Steel Plates against which each friction plate presses), is not driven by the Engine at all.
However In-gear with the Clutch in, DOES drive the clutch basket, BUT the pressure plate, (Large Circular Plate which jams all the individual Clutch Friction Plates against the Steel) is held AWAY from the disks, allowing them to slip past each other. Now they are NOT held away by very much and if you think back to your toast, a thick cold oil (like the honey) between the plates, will actually allow the plates to transfer some of the engines power to the Countershaft and hence to the rear wheel. That's why your rear wheel spins with the bike in gear, clutch in and the bike on the Centrestand.
So what happens is that your poor starter is meeting with resistance, albeit LESS than if you did not use the clutch at all, but quite some resistance nonetheless, and is trying to DRIVE the bike, essentially with the starter alone.! It's like starting your bike or your car in gear without the clutch in, but less severe. If you ever drove a manual car, do you remember learning to drive and forgetting to depress the clutch.? Remember how the car surged forward.? Yup just like that, poor starter motor running off the battery trying to move the ENTIRE car, or bike.
I can't explain why it should move if the gears are in neutral but then again I don't have a cross section of the transmission. Yes, I have had transmissions transmit some power while in neutral but in the cases I can recall due to excessive heat and not excessive cold.
When I get home it should be below zero (F) and I will try my M135GX. Different transmission but a lot more wet clutch packs involved. It's also time I tested the block heater.
Q. Why does the Rear Wheel Turn when the bike is cold and I start in Gear, with the Clutch Pulled in.? Why is it difficult to start.?
A. The F650 has what is called a "Wet" Clutch.
Unlike many cars, where the clutch is separated from the Engine and sump, many bikes have a clutch which runs in an oil bath, the same oil that lubricates the rest of your engine.. You might ask how this works when oil is pretty slippery stuff, but if there are enough plates (The F has 7), strong enough springs there will be enough friction. Plus Oil is a very viscous liquid, so some of the transfer of the engine power across the plates is done though the oil.
A wet clutch has multiple plates running in the engine's motor oil, like the F650 engine. A dry clutch runs in its own housing and consists of one or two plates. Think BMW boxers and Moto Guzzis and most cars and trucks. They both work fine, if properly designed. A wet clutch is typically more compact and will usually engage more progressively, however as it wears, it tends to foul the engine oil with clutch material. Wet clutches are also quieter than dry clutches (think Ducati). Richard #230
Dry clutches last longer, too in most cases. Some are equally quiet, as the BMW dry clutches are noise free. Ducati has the market for noisy clutches! Don't even have to see the bike coming to know what it is. Changing a wet clutch pack is almost always easier than dry bike clutches. More labor involved in most cases, for dry ones. Costs? Wet clutch packs are much cheaper as well, when comparing the BMW clutch assemblies. Feel? Not much difference, these days, but there was a day when the early BMW dry clutches on the early boxers were snatchy! Randy748/Calif
Oil itself, until it breaks down over time or with wear, has a fairly high viscosity for a fluid. Ever dropped a piece of toast with honey on the floor and tried to pick it up sliding it across the floor a bit. Difficult isn't it.? In the same way the very small amount of oil between the plates is the same. Viscosity is temperature-related. When it is cold, oil is "thicker", i.e. has a higher viscosity.
The Clutch comprises a "Basket" Part#1 (External) & Part#2 Internal, Several Friction Disks Part #10, Several Steel Disks Part #11, and a Pressure Plate #12, which jams the whole sandwich together using the springs, 6x Part #1.
The difference between Neutral and in-gear with the Clutch in, is that in Neutral the Clutch Basket, which houses the Clutch Friction Plates and the Smooth Steel Plates against which each friction plate presses), is not driven by the Engine at all.
However In-gear with the Clutch in, DOES drive the clutch basket, BUT the pressure plate, (Large Circular Plate which jams all the individual Clutch Friction Plates against the Steel) is held AWAY from the disks, allowing them to slip past each other. Now they are NOT held away by very much and if you think back to your toast, a thick cold oil (like the honey) between the plates, will actually allow the plates to transfer some of the engines power to the Countershaft and hence to the rear wheel. That's why your rear wheel spins with the bike in gear, clutch in and the bike on the Centrestand.
So what happens is that your poor starter is meeting with resistance, albeit LESS than if you did not use the clutch at all, but quite some resistance nonetheless, and is trying to DRIVE the bike, essentially with the starter alone.! It's like starting your bike or your car in gear without the clutch in, but less severe. If you ever drove a manual car, do you remember learning to drive and forgetting to depress the clutch.? Remember how the car surged forward.? Yup just like that, poor starter motor running off the battery trying to move the ENTIRE car, or bike.
