Centrifugal Clutch One-Way Bearing Won't Engage

[Dustmonkey]

Like KCvale, it has been my understanding that a pull start or powered start is required when using a centrifugal clutch.

Those centrifugal clutches need a bunch of RPM (like a couple thousand) to engage, and it is doubtful that you could pedal the bike fast enough to get the clutch to engage and cycle that force back to the engine to get it to fire.

 

[Steve Best]

Like KCvale, it has been my understanding that a pull start or powered start is required when using a centrifugal clutch.

Those centrifugal clutches need a bunch of RPM (like a couple thousand) to engage, and it is doubtful that you could pedal the bike fast enough to get the clutch to engage and cycle that force back to the engine to get it to fire.

You can't ever pedal a centrifugal clutch fast enough to start. The weighted clutches are on the motor side and unstarted, it does not move.

If however, you had a one way bearing between the motor and the drivetrain it would turn the motor whenever the drive goes faster than the motor, like when bump starting. You would still need the manual clutch lever for pedaling with the motor off but with motor running, it would coast to a stop with no need of the manual clutch. I've never seen it built on a motorized bicycle but we use similar systems in industry to move conveyors from different drive sources or directions. Automatic transmissions use a similar system to get 2 forward and one reverse speed from a single planetary gearset.

 

[Quenton Guenther]

hi,

Whizzer automatic clutches use a one-way bearing to allow pedal starting the motor, however not aware of any other drives that use them. We use the same clutch parts in our 4 stroke drive system as we do in the clutch systems we make for Whizzers, the major difference being the one-way bearing.
Have fun,

 

[KTOKTO]

A pedal start with a centrifgual should be possible with a sprag type of clutch with the manual clutch engaged right? Or am I missing something here? Searching this site for some of the key words pull up conflicting info but there seem to be quite a few people out there who have a one way clutch bearing and are pedal starting their centrifugal clutch bikes.

I've been looking around for vendors of these types of clutches but everything I am finding is either sold out or a vague description in ebay listings.

 

[KTOKTO]

By all means please tell us about this magical CF clutch that apparently don't work!

Is this what you are looking for? Start watching at 18:45 and you will see the sprag catch.

 

[Frankenstein]

Ei yie yie people. On the centrifugal clutch kits for these 2 strokes is rather simple, I think it was Fred who made the video for installation, he even specifically mentioned a one way bearing.

Basically, an extention is placed on the output shaft of the motor, on that shaft, in order from the inside of the motor out, is a clutch bell with a bevel gear on it, inside the gear is a one way bearing, this is an important part to keep lubed, after that is a clutch boot which is directly attached via taper or key to the extention. When the motor turns it will engage the boots with the bell which then turns the bevel gear.

If you pedal the bike to start, then once you let the normal clutch go, and the large clutch gear engages the bell's gear the one way bearing starts turning the motor over because the motor is obviously moving slower than the bell's gear on the outside of the shaft. I drew a picture now stop thinking too much and get all picture book with it.

 

[KTOKTO]

Thanks for the drawing, I get it now. Harry Potter was right!

 

[Frankenstein]

Magic's the best thing to happen to motors since science failed us.

 

[KCvale]

Magic's the best thing to happen to motors since science failed us.

Hehehe...
I use two freewheel (one-way) bearings in my 4-stroke shifters.
One on the output shaft so you don't drag the belt when pedaling with the engine off, the other is for the pedals so they don't move when the engine is on.

Unfortunately I have not seen the magic ones yet ;-}

 

[RoadRunner1973]

Just installed a centrifugal clutch on my 66cc engine (which has been running fine with a friction clutch for 200 miles). Can't pedal it at the moment because the cranks don't clear the case. To try and start it, I just coast down my driveway and then pop the friction clutch. I'm getting nothing but the clutch bell spinning. When i slowly walk the bike, I can get the one way bearing to engage but nothing beyond that and certainly not long enough or securely enough to get the engine to start.

What am I doing wrong? Does the bolt that holds the whole assembly together need to be even tighter?

I had the same problem thanks for the info