A slipper clutch helps prevent rear wheel chatter, hopping, or over-rev due to engine braking when aggressively downshifting. The slipper clutch allows a certain amount of “slip”, reducing the amount of engine braking, allowing the back wheel to spin relatively free.
Slipper clutches have been around a long time, first introduced by Honda back in 1982 on the Honda NR500 GP bike.
What are the mechanics of a slipper clutch?
The most used type of slipper clutch is called the “Ramp” type, so this is what we will focus on. The clutch hub has a number of ramps built into its design. When the rear wheel is trying to spin the engine, it causes the clutch plates to separate slightly.
During deceleration (slip), the clutch plates are forced away from each other, reducing the amount of engagement.
During acceleration (assist or grip), the clutch plates are forced together, increasing the amount of engagement.
The amount of slip applied is important, as enough drag needs to be applied in order to equalize the rear wheel speed against the engine speed, allowing for smooth acceleration when you open the throttle again. But not too much drag, that you load up the engine.
Are slipper clutches reliable?
Slipper clutches have been around for a long time and are generally very reliable. They have become standard kit on many bikes and a popular aftermarket option for those bikes that don’t have a slipper clutch as standard.
Slipper clutches prevent over-revving and reduce the amount of rear-wheel hop, bounce, chatter when you brake hard. This in effect, reduces the overall stress on the complete drive train, increasing the overall life and reliability of the complete system.
Can you bump or jump start with a slipper clutch?
It depends on the amount of slip set up for the clutch. If it’s tight and not allowing much slip, then you might not be able to bump start the bike. Some riders say they can get around this by using a higher gear and dumping the clutch.
Regardless of the slipper clutch set-up, many modern bikes have high compression engines, multiple cylinders, ECU controlled fuel injection systems, electric fuel pumps that require priming, working voltage, plus a decent amount of current/amperage to function, so bump starting is still often a problem even with a normal clutch.
Jump starting should not be a problem, providing you can get enough cranking current/amperage on the starter as you would have with a fully charged battery.
Bottom line… YMMV, all depends on the bike set up, compression ratio, electronics, etc.
This video gives a great overview on how a slipper clutch works.