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Lubrication port > Modified Centrifugal Clutch - 48cc, 60cc, 66cc, 70cc, 80cc - pull-start/pedal-start, 2 stroke

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Lubrication port > Modified Centrifugal Clutch - 48cc, 60cc, 66cc, 70cc, 80cc - pull-start/pedal-start, 2 stroke

Post by Fabian on Mon Jan 16 2012, 04:56

Below are the photos of my (modified) centrifugal clutch, commonly available for 2-stroke, centre mount engines, as an accessory kit, attaching to 48cc, 60cc, 66cc, 70cc and 80cc motors.
Unfortunately the photo compression software on has made the text boxes virtually unreadable.

In short: the centrifugal clutch in it's boxed form lacks any provision for regular lubrication, except for disassembling the clutch itself.
From my experience (and with surprising consistency) the thin film of grease in between crankshaft adapter sleeve and the clutch bell runs dry within 300 kilometers (approx 240 miles), which leads to lockup and damage of the mechanism.
So far, and after modification, my total trip distance has been 800 kilometers with perfect reliability, giving the clutch a small squirt of motorcycle chain lube (ideally with graphite in the lube) every 100 kilometers.
It's important to note that only a small amount of chain lube be used because you are trying to avoid pushing lubricant to the front of the centrifugal clutch where it can be thrown onto the clutch shoes.

A word of caution when drilling through hardened steel with a full cobalt bit: securely mount the clutch bell in a drill press and use the "SLOWEST POSSIBLE RPM and don't be aggressive in using too much downward pressure on the drill bit.
Take your time as you can't rush this part of the process; full cobalt bits are terribly brittle and will easily break if grabbing inside the hole. Be especially slow and gentle when the drill bit is about to break through the surface hardening on the inside diameter of the clutch bell gear.
It's easy to know when you've reached that depth as the bit will be squeaking and squealing; generally making noises of protest and impending doom. If the drill bit is going to break, it will most likely happen at this point.
Treat the drilling process like it is your baby and everything will turn out perfectly. Rush the process and it will end in tears.
Note: Any drill bit used in this process must be "full cobalt".
Start by drilling a 2mm pilot hole (using a drill press) in the middle width of the gear, directly on the base of the tooth profile. You don't want the drill bit to rub or cut into the side of the tooth face and weaken the tooth profile.
Finish up by carefully (and very slowly) running a 2.5mm drill bit through the hole.
This two step process is required because a 2.5mm drill bit is slightly too wide for the bottom of the tooth profile, and will tear away the flutes of the drill bit.
Remember it's a two step process: 2mm full cobalt drill bit, followed by a final pass with a 2.5mm full cobalt drill bit using care and caution and painstakingly slow drill speed and drill pressure.

To make access easier when aligning clutch bell to aerosol tube, simply drill a 6mm hole in the clutch cover and make a 1mm notch in the clutch bell so when the rear wheel is gently turned backwards, the flat blade screw driver catches in the notch, as shown in the photos.
Once the system has been lubricated, place a 6mm grommet or rubber blanking plug in the clutch cover access hole and use a wide rubber band wrapped around the centrifugal clutch case to cover the 2.5mm access hole for aerosol tube insertion.
It might be a simple solution but it works perfectly.

A point of note is that the centrifugal clutch will need to be lubricated more often if the bicycle power delivery setup is single speed, as per the standard engine kits.
This style of setup has the centrifugal clutch slipping for a significantly longer duration when accelerating from standstill than a multi-gear enabled system, like the SickBikeParts shift kit.
The following two photos explain why the Chinese 2-stroke bicycle engine accessory kit will quickly burn up any lubrication between the surfaces of clutch bell and crankshaft extension sleeve, if excessive slippage is forced on the system for an extended period of time.
By far the best way to reduce slippage from a standing start is to reduce the load on the centrifugal clutch, and the best way to reduce the load is to purchase a multi-gear enabled system like the SickBikeParts shift kit, or any other similar device.
Single speed systems might be cheap and simple but it's like driving around in high gear all the time.
How long would a car clutch last if trying to to accelerate from endless sets of traffic lights in top gear; without any lubrication in the bearings.



If the modification shown in the (below) photos are of help, as to providing a reliable centrifugal clutch and you want more info or instructions, my email address is:














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